diff --git a/src/applications/paste/controller/PhabricatorPasteEditController.php b/src/applications/paste/controller/PhabricatorPasteEditController.php
index 7aa28673da..dcc4900951 100644
--- a/src/applications/paste/controller/PhabricatorPasteEditController.php
+++ b/src/applications/paste/controller/PhabricatorPasteEditController.php
@@ -1,249 +1,244 @@
 <?php
 
 final class PhabricatorPasteEditController extends PhabricatorPasteController {
 
   private $id;
 
   public function willProcessRequest(array $data) {
     $this->id = idx($data, 'id');
   }
 
   public function processRequest() {
     $request = $this->getRequest();
     $user = $request->getUser();
 
     $parent = null;
     $parent_id = null;
     if (!$this->id) {
       $is_create = true;
 
       $paste = PhabricatorPaste::initializeNewPaste($user);
 
       $parent_id = $request->getStr('parent');
       if ($parent_id) {
         // NOTE: If the Paste is forked from a paste which the user no longer
         // has permission to see, we still let them edit it.
         $parent = id(new PhabricatorPasteQuery())
           ->setViewer($user)
           ->withIDs(array($parent_id))
           ->needContent(true)
           ->needRawContent(true)
           ->execute();
         $parent = head($parent);
 
         if ($parent) {
           $paste->setParentPHID($parent->getPHID());
           $paste->setViewPolicy($parent->getViewPolicy());
         }
       }
 
       $paste->setAuthorPHID($user->getPHID());
       $paste->attachRawContent('');
     } else {
       $is_create = false;
 
       $paste = id(new PhabricatorPasteQuery())
         ->setViewer($user)
         ->requireCapabilities(
           array(
             PhabricatorPolicyCapability::CAN_VIEW,
             PhabricatorPolicyCapability::CAN_EDIT,
           ))
         ->withIDs(array($this->id))
         ->needRawContent(true)
         ->executeOne();
       if (!$paste) {
         return new Aphront404Response();
       }
     }
 
     $v_space = $paste->getSpacePHID();
     if ($is_create && $parent) {
       $v_title = pht('Fork of %s', $parent->getFullName());
       $v_language = $parent->getLanguage();
       $v_text = $parent->getRawContent();
       $v_space = $parent->getSpacePHID();
     } else {
       $v_title = $paste->getTitle();
       $v_language = $paste->getLanguage();
       $v_text = $paste->getRawContent();
     }
     $v_view_policy = $paste->getViewPolicy();
     $v_edit_policy = $paste->getEditPolicy();
 
     if ($is_create) {
       $v_projects = array();
     } else {
       $v_projects = PhabricatorEdgeQuery::loadDestinationPHIDs(
         $paste->getPHID(),
         PhabricatorProjectObjectHasProjectEdgeType::EDGECONST);
       $v_projects = array_reverse($v_projects);
     }
 
     $validation_exception = null;
     if ($request->isFormPost()) {
       $xactions = array();
 
       $v_text = $request->getStr('text');
       $v_title = $request->getStr('title');
       $v_language = $request->getStr('language');
       $v_view_policy = $request->getStr('can_view');
       $v_edit_policy = $request->getStr('can_edit');
       $v_projects = $request->getArr('projects');
       $v_space = $request->getStr('spacePHID');
 
       // NOTE: The author is the only editor and can always view the paste,
       // so it's impossible for them to choose an invalid policy.
 
       if ($is_create || ($v_text !== $paste->getRawContent())) {
         $file = PhabricatorPasteEditor::initializeFileForPaste(
           $user,
           $v_title,
           $v_text);
 
         $xactions[] = id(new PhabricatorPasteTransaction())
           ->setTransactionType(PhabricatorPasteTransaction::TYPE_CONTENT)
           ->setNewValue($file->getPHID());
       }
 
       $xactions[] = id(new PhabricatorPasteTransaction())
         ->setTransactionType(PhabricatorPasteTransaction::TYPE_TITLE)
         ->setNewValue($v_title);
       $xactions[] = id(new PhabricatorPasteTransaction())
         ->setTransactionType(PhabricatorPasteTransaction::TYPE_LANGUAGE)
         ->setNewValue($v_language);
       $xactions[] = id(new PhabricatorPasteTransaction())
         ->setTransactionType(PhabricatorTransactions::TYPE_VIEW_POLICY)
         ->setNewValue($v_view_policy);
       $xactions[] = id(new PhabricatorPasteTransaction())
         ->setTransactionType(PhabricatorTransactions::TYPE_EDIT_POLICY)
         ->setNewValue($v_edit_policy);
       $xactions[] = id(new PhabricatorPasteTransaction())
         ->setTransactionType(PhabricatorTransactions::TYPE_SPACE)
         ->setNewValue($v_space);
 
       $proj_edge_type = PhabricatorProjectObjectHasProjectEdgeType::EDGECONST;
       $xactions[] = id(new PhabricatorPasteTransaction())
         ->setTransactionType(PhabricatorTransactions::TYPE_EDGE)
         ->setMetadataValue('edge:type', $proj_edge_type)
         ->setNewValue(array('=' => array_fuse($v_projects)));
 
       $editor = id(new PhabricatorPasteEditor())
         ->setActor($user)
         ->setContentSourceFromRequest($request)
         ->setContinueOnNoEffect(true);
 
       try {
         $xactions = $editor->applyTransactions($paste, $xactions);
         return id(new AphrontRedirectResponse())->setURI($paste->getURI());
       } catch (PhabricatorApplicationTransactionValidationException $ex) {
         $validation_exception = $ex;
       }
     }
 
     $form = new AphrontFormView();
 
     $langs = array(
       '' => pht('(Detect From Filename in Title)'),
     ) + PhabricatorEnv::getEnvConfig('pygments.dropdown-choices');
 
     $form
       ->setUser($user)
       ->addHiddenInput('parent', $parent_id)
       ->appendChild(
         id(new AphrontFormTextControl())
           ->setLabel(pht('Title'))
           ->setValue($v_title)
           ->setName('title'))
       ->appendChild(
         id(new AphrontFormSelectControl())
           ->setLabel(pht('Language'))
           ->setName('language')
           ->setValue($v_language)
           ->setOptions($langs));
 
     $policies = id(new PhabricatorPolicyQuery())
       ->setViewer($user)
       ->setObject($paste)
       ->execute();
 
-    $form->appendControl(
-      id(new PhabricatorSpacesControl())
-        ->setObject($paste)
-        ->setValue($v_space)
-        ->setName('spacePHID'));
-
     $form->appendChild(
       id(new AphrontFormPolicyControl())
         ->setUser($user)
         ->setCapability(PhabricatorPolicyCapability::CAN_VIEW)
         ->setPolicyObject($paste)
         ->setPolicies($policies)
         ->setValue($v_view_policy)
+        ->setSpacePHID($v_space)
         ->setName('can_view'));
 
     $form->appendChild(
       id(new AphrontFormPolicyControl())
         ->setUser($user)
         ->setCapability(PhabricatorPolicyCapability::CAN_EDIT)
         ->setPolicyObject($paste)
         ->setPolicies($policies)
         ->setValue($v_edit_policy)
         ->setName('can_edit'));
 
     $form->appendControl(
       id(new AphrontFormTokenizerControl())
         ->setLabel(pht('Projects'))
         ->setName('projects')
         ->setValue($v_projects)
         ->setDatasource(new PhabricatorProjectDatasource()));
 
     $form
       ->appendChild(
         id(new AphrontFormTextAreaControl())
           ->setLabel(pht('Text'))
           ->setValue($v_text)
           ->setHeight(AphrontFormTextAreaControl::HEIGHT_VERY_TALL)
           ->setCustomClass('PhabricatorMonospaced')
           ->setName('text'));
 
     $submit = new AphrontFormSubmitControl();
 
     if (!$is_create) {
       $submit->addCancelButton($paste->getURI());
       $submit->setValue(pht('Save Paste'));
       $title = pht('Edit %s', $paste->getFullName());
       $short = pht('Edit');
     } else {
       $submit->setValue(pht('Create Paste'));
       $title = pht('Create New Paste');
       $short = pht('Create');
     }
 
     $form->appendChild($submit);
 
     $form_box = id(new PHUIObjectBoxView())
       ->setHeaderText($title)
       ->setForm($form);
 
     if ($validation_exception) {
       $form_box->setValidationException($validation_exception);
     }
 
     $crumbs = $this->buildApplicationCrumbs($this->buildSideNavView());
     if (!$is_create) {
       $crumbs->addTextCrumb('P'.$paste->getID(), '/P'.$paste->getID());
     }
     $crumbs->addTextCrumb($short);
 
     return $this->buildApplicationPage(
       array(
         $crumbs,
         $form_box,
       ),
       array(
         'title' => $title,
       ));
   }
 
 }
diff --git a/src/applications/people/storage/PhabricatorUser.php b/src/applications/people/storage/PhabricatorUser.php
index d86f5e380d..aa93485dd2 100644
--- a/src/applications/people/storage/PhabricatorUser.php
+++ b/src/applications/people/storage/PhabricatorUser.php
@@ -1,1241 +1,1250 @@
 <?php
 
 /**
  * @task availability Availability
  * @task image-cache Profile Image Cache
  * @task factors Multi-Factor Authentication
  * @task handles Managing Handles
  */
 final class PhabricatorUser
   extends PhabricatorUserDAO
   implements
     PhutilPerson,
     PhabricatorPolicyInterface,
     PhabricatorCustomFieldInterface,
     PhabricatorDestructibleInterface,
     PhabricatorSSHPublicKeyInterface,
     PhabricatorApplicationTransactionInterface {
 
   const SESSION_TABLE = 'phabricator_session';
   const NAMETOKEN_TABLE = 'user_nametoken';
   const MAXIMUM_USERNAME_LENGTH = 64;
 
   protected $userName;
   protected $realName;
   protected $sex;
   protected $translation;
   protected $passwordSalt;
   protected $passwordHash;
   protected $profileImagePHID;
   protected $profileImageCache;
   protected $availabilityCache;
   protected $availabilityCacheTTL;
   protected $timezoneIdentifier = '';
 
   protected $consoleEnabled = 0;
   protected $consoleVisible = 0;
   protected $consoleTab = '';
 
   protected $conduitCertificate;
 
   protected $isSystemAgent = 0;
   protected $isMailingList = 0;
   protected $isAdmin = 0;
   protected $isDisabled = 0;
   protected $isEmailVerified = 0;
   protected $isApproved = 0;
   protected $isEnrolledInMultiFactor = 0;
 
   protected $accountSecret;
 
   private $profileImage = self::ATTACHABLE;
   private $profile = null;
   private $availability = self::ATTACHABLE;
   private $preferences = null;
   private $omnipotent = false;
   private $customFields = self::ATTACHABLE;
 
   private $alternateCSRFString = self::ATTACHABLE;
   private $session = self::ATTACHABLE;
 
   private $authorities = array();
   private $handlePool;
   private $csrfSalt;
 
   protected function readField($field) {
     switch ($field) {
       case 'timezoneIdentifier':
         // If the user hasn't set one, guess the server's time.
         return nonempty(
           $this->timezoneIdentifier,
           date_default_timezone_get());
       // Make sure these return booleans.
       case 'isAdmin':
         return (bool)$this->isAdmin;
       case 'isDisabled':
         return (bool)$this->isDisabled;
       case 'isSystemAgent':
         return (bool)$this->isSystemAgent;
       case 'isMailingList':
         return (bool)$this->isMailingList;
       case 'isEmailVerified':
         return (bool)$this->isEmailVerified;
       case 'isApproved':
         return (bool)$this->isApproved;
       default:
         return parent::readField($field);
     }
   }
 
 
   /**
    * Is this a live account which has passed required approvals? Returns true
    * if this is an enabled, verified (if required), approved (if required)
    * account, and false otherwise.
    *
    * @return bool True if this is a standard, usable account.
    */
   public function isUserActivated() {
     if ($this->isOmnipotent()) {
       return true;
     }
 
     if ($this->getIsDisabled()) {
       return false;
     }
 
     if (!$this->getIsApproved()) {
       return false;
     }
 
     if (PhabricatorUserEmail::isEmailVerificationRequired()) {
       if (!$this->getIsEmailVerified()) {
         return false;
       }
     }
 
     return true;
   }
 
   public function canEstablishWebSessions() {
     if ($this->getIsMailingList()) {
       return false;
     }
 
     if ($this->getIsSystemAgent()) {
       return false;
     }
 
     return true;
   }
 
   public function canEstablishAPISessions() {
     if (!$this->isUserActivated()) {
       return false;
     }
 
     if ($this->getIsMailingList()) {
       return false;
     }
 
     return true;
   }
 
   public function canEstablishSSHSessions() {
     if (!$this->isUserActivated()) {
       return false;
     }
 
     if ($this->getIsMailingList()) {
       return false;
     }
 
     return true;
   }
 
   /**
    * Returns `true` if this is a standard user who is logged in. Returns `false`
    * for logged out, anonymous, or external users.
    *
    * @return bool `true` if the user is a standard user who is logged in with
    *              a normal session.
    */
   public function getIsStandardUser() {
     $type_user = PhabricatorPeopleUserPHIDType::TYPECONST;
     return $this->getPHID() && (phid_get_type($this->getPHID()) == $type_user);
   }
 
   protected function getConfiguration() {
     return array(
       self::CONFIG_AUX_PHID => true,
       self::CONFIG_COLUMN_SCHEMA => array(
         'userName' => 'sort64',
         'realName' => 'text128',
         'sex' => 'text4?',
         'translation' => 'text64?',
         'passwordSalt' => 'text32?',
         'passwordHash' => 'text128?',
         'profileImagePHID' => 'phid?',
         'consoleEnabled' => 'bool',
         'consoleVisible' => 'bool',
         'consoleTab' => 'text64',
         'conduitCertificate' => 'text255',
         'isSystemAgent' => 'bool',
         'isMailingList' => 'bool',
         'isDisabled' => 'bool',
         'isAdmin' => 'bool',
         'timezoneIdentifier' => 'text255',
         'isEmailVerified' => 'uint32',
         'isApproved' => 'uint32',
         'accountSecret' => 'bytes64',
         'isEnrolledInMultiFactor' => 'bool',
         'profileImageCache' => 'text255?',
         'availabilityCache' => 'text255?',
         'availabilityCacheTTL' => 'uint32?',
       ),
       self::CONFIG_KEY_SCHEMA => array(
         'key_phid' => null,
         'phid' => array(
           'columns' => array('phid'),
           'unique' => true,
         ),
         'userName' => array(
           'columns' => array('userName'),
           'unique' => true,
         ),
         'realName' => array(
           'columns' => array('realName'),
         ),
         'key_approved' => array(
           'columns' => array('isApproved'),
         ),
       ),
       self::CONFIG_NO_MUTATE => array(
         'profileImageCache' => true,
         'availabilityCache' => true,
         'availabilityCacheTTL' => true,
       ),
     ) + parent::getConfiguration();
   }
 
   public function generatePHID() {
     return PhabricatorPHID::generateNewPHID(
       PhabricatorPeopleUserPHIDType::TYPECONST);
   }
 
   public function setPassword(PhutilOpaqueEnvelope $envelope) {
     if (!$this->getPHID()) {
       throw new Exception(
         pht(
           'You can not set a password for an unsaved user because their PHID '.
           'is a salt component in the password hash.'));
     }
 
     if (!strlen($envelope->openEnvelope())) {
       $this->setPasswordHash('');
     } else {
       $this->setPasswordSalt(md5(Filesystem::readRandomBytes(32)));
       $hash = $this->hashPassword($envelope);
       $this->setPasswordHash($hash->openEnvelope());
     }
     return $this;
   }
 
   // To satisfy PhutilPerson.
   public function getSex() {
     return $this->sex;
   }
 
   public function getMonogram() {
     return '@'.$this->getUsername();
   }
 
   public function isLoggedIn() {
     return !($this->getPHID() === null);
   }
 
   public function save() {
     if (!$this->getConduitCertificate()) {
       $this->setConduitCertificate($this->generateConduitCertificate());
     }
 
     if (!strlen($this->getAccountSecret())) {
       $this->setAccountSecret(Filesystem::readRandomCharacters(64));
     }
 
     $result = parent::save();
 
     if ($this->profile) {
       $this->profile->save();
     }
 
     $this->updateNameTokens();
 
     id(new PhabricatorSearchIndexer())
       ->queueDocumentForIndexing($this->getPHID());
 
     return $result;
   }
 
   public function attachSession(PhabricatorAuthSession $session) {
     $this->session = $session;
     return $this;
   }
 
   public function getSession() {
     return $this->assertAttached($this->session);
   }
 
   public function hasSession() {
     return ($this->session !== self::ATTACHABLE);
   }
 
   private function generateConduitCertificate() {
     return Filesystem::readRandomCharacters(255);
   }
 
   public function comparePassword(PhutilOpaqueEnvelope $envelope) {
     if (!strlen($envelope->openEnvelope())) {
       return false;
     }
     if (!strlen($this->getPasswordHash())) {
       return false;
     }
 
     return PhabricatorPasswordHasher::comparePassword(
       $this->getPasswordHashInput($envelope),
       new PhutilOpaqueEnvelope($this->getPasswordHash()));
   }
 
   private function getPasswordHashInput(PhutilOpaqueEnvelope $password) {
     $input =
       $this->getUsername().
       $password->openEnvelope().
       $this->getPHID().
       $this->getPasswordSalt();
 
     return new PhutilOpaqueEnvelope($input);
   }
 
   private function hashPassword(PhutilOpaqueEnvelope $password) {
     $hasher = PhabricatorPasswordHasher::getBestHasher();
 
     $input_envelope = $this->getPasswordHashInput($password);
     return $hasher->getPasswordHashForStorage($input_envelope);
   }
 
   const CSRF_CYCLE_FREQUENCY  = 3600;
   const CSRF_SALT_LENGTH      = 8;
   const CSRF_TOKEN_LENGTH     = 16;
   const CSRF_BREACH_PREFIX    = 'B@';
 
   const EMAIL_CYCLE_FREQUENCY = 86400;
   const EMAIL_TOKEN_LENGTH    = 24;
 
   private function getRawCSRFToken($offset = 0) {
     return $this->generateToken(
       time() + (self::CSRF_CYCLE_FREQUENCY * $offset),
       self::CSRF_CYCLE_FREQUENCY,
       PhabricatorEnv::getEnvConfig('phabricator.csrf-key'),
       self::CSRF_TOKEN_LENGTH);
   }
 
   public function getCSRFToken() {
     if ($this->isOmnipotent()) {
       // We may end up here when called from the daemons. The omnipotent user
       // has no meaningful CSRF token, so just return `null`.
       return null;
     }
 
     if ($this->csrfSalt === null) {
       $this->csrfSalt = Filesystem::readRandomCharacters(
         self::CSRF_SALT_LENGTH);
     }
 
     $salt = $this->csrfSalt;
 
     // Generate a token hash to mitigate BREACH attacks against SSL. See
     // discussion in T3684.
     $token = $this->getRawCSRFToken();
     $hash = PhabricatorHash::digest($token, $salt);
     return self::CSRF_BREACH_PREFIX.$salt.substr(
         $hash, 0, self::CSRF_TOKEN_LENGTH);
   }
 
   public function validateCSRFToken($token) {
     $salt = null;
     $version = 'plain';
 
     // This is a BREACH-mitigating token. See T3684.
     $breach_prefix = self::CSRF_BREACH_PREFIX;
     $breach_prelen = strlen($breach_prefix);
 
     if (!strncmp($token, $breach_prefix, $breach_prelen)) {
       $version = 'breach';
       $salt = substr($token, $breach_prelen, self::CSRF_SALT_LENGTH);
       $token = substr($token, $breach_prelen + self::CSRF_SALT_LENGTH);
     }
 
     // When the user posts a form, we check that it contains a valid CSRF token.
     // Tokens cycle each hour (every CSRF_CYLCE_FREQUENCY seconds) and we accept
     // either the current token, the next token (users can submit a "future"
     // token if you have two web frontends that have some clock skew) or any of
     // the last 6 tokens. This means that pages are valid for up to 7 hours.
     // There is also some Javascript which periodically refreshes the CSRF
     // tokens on each page, so theoretically pages should be valid indefinitely.
     // However, this code may fail to run (if the user loses their internet
     // connection, or there's a JS problem, or they don't have JS enabled).
     // Choosing the size of the window in which we accept old CSRF tokens is
     // an issue of balancing concerns between security and usability. We could
     // choose a very narrow (e.g., 1-hour) window to reduce vulnerability to
     // attacks using captured CSRF tokens, but it's also more likely that real
     // users will be affected by this, e.g. if they close their laptop for an
     // hour, open it back up, and try to submit a form before the CSRF refresh
     // can kick in. Since the user experience of submitting a form with expired
     // CSRF is often quite bad (you basically lose data, or it's a big pain to
     // recover at least) and I believe we gain little additional protection
     // by keeping the window very short (the overwhelming value here is in
     // preventing blind attacks, and most attacks which can capture CSRF tokens
     // can also just capture authentication information [sniffing networks]
     // or act as the user [xss]) the 7 hour default seems like a reasonable
     // balance. Other major platforms have much longer CSRF token lifetimes,
     // like Rails (session duration) and Django (forever), which suggests this
     // is a reasonable analysis.
     $csrf_window = 6;
 
     for ($ii = -$csrf_window; $ii <= 1; $ii++) {
       $valid = $this->getRawCSRFToken($ii);
       switch ($version) {
         // TODO: We can remove this after the BREACH version has been in the
         // wild for a while.
         case 'plain':
           if ($token == $valid) {
             return true;
           }
           break;
         case 'breach':
           $digest = PhabricatorHash::digest($valid, $salt);
           if (substr($digest, 0, self::CSRF_TOKEN_LENGTH) == $token) {
             return true;
           }
           break;
         default:
           throw new Exception(pht('Unknown CSRF token format!'));
       }
     }
 
     return false;
   }
 
   private function generateToken($epoch, $frequency, $key, $len) {
     if ($this->getPHID()) {
       $vec = $this->getPHID().$this->getAccountSecret();
     } else {
       $vec = $this->getAlternateCSRFString();
     }
 
     if ($this->hasSession()) {
       $vec = $vec.$this->getSession()->getSessionKey();
     }
 
     $time_block = floor($epoch / $frequency);
     $vec = $vec.$key.$time_block;
 
     return substr(PhabricatorHash::digest($vec), 0, $len);
   }
 
   public function getUserProfile() {
     return $this->assertAttached($this->profile);
   }
 
   public function attachUserProfile(PhabricatorUserProfile $profile) {
     $this->profile = $profile;
     return $this;
   }
 
   public function loadUserProfile() {
     if ($this->profile) {
       return $this->profile;
     }
 
     $profile_dao = new PhabricatorUserProfile();
     $this->profile = $profile_dao->loadOneWhere('userPHID = %s',
       $this->getPHID());
 
     if (!$this->profile) {
       $profile_dao->setUserPHID($this->getPHID());
       $this->profile = $profile_dao;
     }
 
     return $this->profile;
   }
 
   public function loadPrimaryEmailAddress() {
     $email = $this->loadPrimaryEmail();
     if (!$email) {
       throw new Exception(pht('User has no primary email address!'));
     }
     return $email->getAddress();
   }
 
   public function loadPrimaryEmail() {
     return $this->loadOneRelative(
       new PhabricatorUserEmail(),
       'userPHID',
       'getPHID',
       '(isPrimary = 1)');
   }
 
   public function loadPreferences() {
     if ($this->preferences) {
       return $this->preferences;
     }
 
     $preferences = null;
     if ($this->getPHID()) {
       $preferences = id(new PhabricatorUserPreferences())->loadOneWhere(
         'userPHID = %s',
         $this->getPHID());
     }
 
     if (!$preferences) {
       $preferences = new PhabricatorUserPreferences();
       $preferences->setUserPHID($this->getPHID());
 
       $default_dict = array(
         PhabricatorUserPreferences::PREFERENCE_TITLES => 'glyph',
         PhabricatorUserPreferences::PREFERENCE_EDITOR => '',
         PhabricatorUserPreferences::PREFERENCE_MONOSPACED => '',
         PhabricatorUserPreferences::PREFERENCE_DARK_CONSOLE => 0,
       );
 
       $preferences->setPreferences($default_dict);
     }
 
     $this->preferences = $preferences;
     return $preferences;
   }
 
   public function loadEditorLink($path, $line, $callsign) {
     $editor = $this->loadPreferences()->getPreference(
       PhabricatorUserPreferences::PREFERENCE_EDITOR);
 
     if (is_array($path)) {
       $multiedit = $this->loadPreferences()->getPreference(
         PhabricatorUserPreferences::PREFERENCE_MULTIEDIT);
       switch ($multiedit) {
         case '':
           $path = implode(' ', $path);
           break;
         case 'disable':
           return null;
       }
     }
 
     if (!strlen($editor)) {
       return null;
     }
 
     $uri = strtr($editor, array(
       '%%' => '%',
       '%f' => phutil_escape_uri($path),
       '%l' => phutil_escape_uri($line),
       '%r' => phutil_escape_uri($callsign),
     ));
 
     // The resulting URI must have an allowed protocol. Otherwise, we'll return
     // a link to an error page explaining the misconfiguration.
 
     $ok = PhabricatorHelpEditorProtocolController::hasAllowedProtocol($uri);
     if (!$ok) {
       return '/help/editorprotocol/';
     }
 
     return (string)$uri;
   }
 
   public function getAlternateCSRFString() {
     return $this->assertAttached($this->alternateCSRFString);
   }
 
   public function attachAlternateCSRFString($string) {
     $this->alternateCSRFString = $string;
     return $this;
   }
 
   /**
    * Populate the nametoken table, which used to fetch typeahead results. When
    * a user types "linc", we want to match "Abraham Lincoln" from on-demand
    * typeahead sources. To do this, we need a separate table of name fragments.
    */
   public function updateNameTokens() {
     $table  = self::NAMETOKEN_TABLE;
     $conn_w = $this->establishConnection('w');
 
     $tokens = PhabricatorTypeaheadDatasource::tokenizeString(
       $this->getUserName().' '.$this->getRealName());
 
     $sql = array();
     foreach ($tokens as $token) {
       $sql[] = qsprintf(
         $conn_w,
         '(%d, %s)',
         $this->getID(),
         $token);
     }
 
     queryfx(
       $conn_w,
       'DELETE FROM %T WHERE userID = %d',
       $table,
       $this->getID());
     if ($sql) {
       queryfx(
         $conn_w,
         'INSERT INTO %T (userID, token) VALUES %Q',
         $table,
         implode(', ', $sql));
     }
   }
 
   public function sendWelcomeEmail(PhabricatorUser $admin) {
     $admin_username = $admin->getUserName();
     $admin_realname = $admin->getRealName();
     $user_username = $this->getUserName();
     $is_serious = PhabricatorEnv::getEnvConfig('phabricator.serious-business');
 
     $base_uri = PhabricatorEnv::getProductionURI('/');
 
     $engine = new PhabricatorAuthSessionEngine();
     $uri = $engine->getOneTimeLoginURI(
       $this,
       $this->loadPrimaryEmail(),
       PhabricatorAuthSessionEngine::ONETIME_WELCOME);
 
     $body = pht(
       "Welcome to Phabricator!\n\n".
       "%s (%s) has created an account for you.\n\n".
       "  Username: %s\n\n".
       "To login to Phabricator, follow this link and set a password:\n\n".
       "  %s\n\n".
       "After you have set a password, you can login in the future by ".
       "going here:\n\n".
       "  %s\n",
       $admin_username,
       $admin_realname,
       $user_username,
       $uri,
       $base_uri);
 
     if (!$is_serious) {
       $body .= sprintf(
         "\n%s\n",
         pht("Love,\nPhabricator"));
     }
 
     $mail = id(new PhabricatorMetaMTAMail())
       ->addTos(array($this->getPHID()))
       ->setForceDelivery(true)
       ->setSubject(pht('[Phabricator] Welcome to Phabricator'))
       ->setBody($body)
       ->saveAndSend();
   }
 
   public function sendUsernameChangeEmail(
     PhabricatorUser $admin,
     $old_username) {
 
     $admin_username = $admin->getUserName();
     $admin_realname = $admin->getRealName();
     $new_username = $this->getUserName();
 
     $password_instructions = null;
     if (PhabricatorPasswordAuthProvider::getPasswordProvider()) {
       $engine = new PhabricatorAuthSessionEngine();
       $uri = $engine->getOneTimeLoginURI(
         $this,
         null,
         PhabricatorAuthSessionEngine::ONETIME_USERNAME);
       $password_instructions = sprintf(
         "%s\n\n  %s\n\n%s\n",
         pht(
           "If you use a password to login, you'll need to reset it ".
           "before you can login again. You can reset your password by ".
           "following this link:"),
         $uri,
         pht(
           "And, of course, you'll need to use your new username to login ".
           "from now on. If you use OAuth to login, nothing should change."));
     }
 
     $body = sprintf(
       "%s\n\n  %s\n  %s\n\n%s",
       pht(
         '%s (%s) has changed your Phabricator username.',
         $admin_username,
         $admin_realname),
       pht(
         'Old Username: %s',
         $old_username),
       pht(
         'New Username: %s',
         $new_username),
       $password_instructions);
 
     $mail = id(new PhabricatorMetaMTAMail())
       ->addTos(array($this->getPHID()))
       ->setForceDelivery(true)
       ->setSubject(pht('[Phabricator] Username Changed'))
       ->setBody($body)
       ->saveAndSend();
   }
 
   public static function describeValidUsername() {
     return pht(
       'Usernames must contain only numbers, letters, period, underscore and '.
       'hyphen, and can not end with a period. They must have no more than %d '.
       'characters.',
       new PhutilNumber(self::MAXIMUM_USERNAME_LENGTH));
   }
 
   public static function validateUsername($username) {
     // NOTE: If you update this, make sure to update:
     //
     //  - Remarkup rule for @mentions.
     //  - Routing rule for "/p/username/".
     //  - Unit tests, obviously.
     //  - describeValidUsername() method, above.
 
     if (strlen($username) > self::MAXIMUM_USERNAME_LENGTH) {
       return false;
     }
 
     return (bool)preg_match('/^[a-zA-Z0-9._-]*[a-zA-Z0-9_-]\z/', $username);
   }
 
   public static function getDefaultProfileImageURI() {
     return celerity_get_resource_uri('/rsrc/image/avatar.png');
   }
 
   public function attachProfileImageURI($uri) {
     $this->profileImage = $uri;
     return $this;
   }
 
   public function getProfileImageURI() {
     return $this->assertAttached($this->profileImage);
   }
 
   public function getFullName() {
     if (strlen($this->getRealName())) {
       return $this->getUsername().' ('.$this->getRealName().')';
     } else {
       return $this->getUsername();
     }
   }
 
   public function getTimeZone() {
     return new DateTimeZone($this->getTimezoneIdentifier());
   }
 
   public function __toString() {
     return $this->getUsername();
   }
 
   public static function loadOneWithEmailAddress($address) {
     $email = id(new PhabricatorUserEmail())->loadOneWhere(
       'address = %s',
       $address);
     if (!$email) {
       return null;
     }
     return id(new PhabricatorUser())->loadOneWhere(
       'phid = %s',
       $email->getUserPHID());
   }
 
   public function getDefaultSpacePHID() {
     // TODO: We might let the user switch which space they're "in" later on;
     // for now just use the global space if one exists.
 
+    // If the viewer has access to the default space, use that.
     $spaces = PhabricatorSpacesNamespaceQuery::getViewerSpaces($this);
     foreach ($spaces as $space) {
       if ($space->getIsDefaultNamespace()) {
         return $space->getPHID();
       }
     }
 
+    // Otherwise, use the space with the lowest ID that they have access to.
+    // This just tends to keep the default stable and predictable over time,
+    // so adding a new space won't change behavior for users.
+    if ($spaces) {
+      $spaces = msort($spaces, 'getID');
+      return head($spaces)->getPHID();
+    }
+
     return null;
   }
 
 
   /**
    * Grant a user a source of authority, to let them bypass policy checks they
    * could not otherwise.
    */
   public function grantAuthority($authority) {
     $this->authorities[] = $authority;
     return $this;
   }
 
 
   /**
    * Get authorities granted to the user.
    */
   public function getAuthorities() {
     return $this->authorities;
   }
 
 
 /* -(  Availability  )------------------------------------------------------- */
 
 
   /**
    * @task availability
    */
   public function attachAvailability(array $availability) {
     $this->availability = $availability;
     return $this;
   }
 
 
   /**
    * Get the timestamp the user is away until, if they are currently away.
    *
    * @return int|null Epoch timestamp, or `null` if the user is not away.
    * @task availability
    */
   public function getAwayUntil() {
     $availability = $this->availability;
 
     $this->assertAttached($availability);
     if (!$availability) {
       return null;
     }
 
     return idx($availability, 'until');
   }
 
 
   /**
    * Describe the user's availability.
    *
    * @param PhabricatorUser Viewing user.
    * @return string Human-readable description of away status.
    * @task availability
    */
   public function getAvailabilityDescription(PhabricatorUser $viewer) {
     $until = $this->getAwayUntil();
     if ($until) {
       return pht('Away until %s', phabricator_datetime($until, $viewer));
     } else {
       return pht('Available');
     }
   }
 
 
   /**
    * Get cached availability, if present.
    *
    * @return wild|null Cache data, or null if no cache is available.
    * @task availability
    */
   public function getAvailabilityCache() {
     $now = PhabricatorTime::getNow();
     if ($this->availabilityCacheTTL <= $now) {
       return null;
     }
 
     try {
       return phutil_json_decode($this->availabilityCache);
     } catch (Exception $ex) {
       return null;
     }
   }
 
 
   /**
    * Write to the availability cache.
    *
    * @param wild Availability cache data.
    * @param int|null Cache TTL.
    * @return this
    * @task availability
    */
   public function writeAvailabilityCache(array $availability, $ttl) {
     $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
     queryfx(
       $this->establishConnection('w'),
       'UPDATE %T SET availabilityCache = %s, availabilityCacheTTL = %nd
         WHERE id = %d',
       $this->getTableName(),
       json_encode($availability),
       $ttl,
       $this->getID());
     unset($unguarded);
 
     return $this;
   }
 
 
 /* -(  Profile Image Cache  )------------------------------------------------ */
 
 
   /**
    * Get this user's cached profile image URI.
    *
    * @return string|null Cached URI, if a URI is cached.
    * @task image-cache
    */
   public function getProfileImageCache() {
     $version = $this->getProfileImageVersion();
 
     $parts = explode(',', $this->profileImageCache, 2);
     if (count($parts) !== 2) {
       return null;
     }
 
     if ($parts[0] !== $version) {
       return null;
     }
 
     return $parts[1];
   }
 
 
   /**
    * Generate a new cache value for this user's profile image.
    *
    * @return string New cache value.
    * @task image-cache
    */
   public function writeProfileImageCache($uri) {
     $version = $this->getProfileImageVersion();
     $cache = "{$version},{$uri}";
 
     $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
     queryfx(
       $this->establishConnection('w'),
       'UPDATE %T SET profileImageCache = %s WHERE id = %d',
       $this->getTableName(),
       $cache,
       $this->getID());
     unset($unguarded);
   }
 
 
   /**
    * Get a version identifier for a user's profile image.
    *
    * This version will change if the image changes, or if any of the
    * environment configuration which goes into generating a URI changes.
    *
    * @return string Cache version.
    * @task image-cache
    */
   private function getProfileImageVersion() {
     $parts = array(
       PhabricatorEnv::getCDNURI('/'),
       PhabricatorEnv::getEnvConfig('cluster.instance'),
       $this->getProfileImagePHID(),
     );
     $parts = serialize($parts);
     return PhabricatorHash::digestForIndex($parts);
   }
 
 
 /* -(  Multi-Factor Authentication  )---------------------------------------- */
 
 
   /**
    * Update the flag storing this user's enrollment in multi-factor auth.
    *
    * With certain settings, we need to check if a user has MFA on every page,
    * so we cache MFA enrollment on the user object for performance. Calling this
    * method synchronizes the cache by examining enrollment records. After
    * updating the cache, use @{method:getIsEnrolledInMultiFactor} to check if
    * the user is enrolled.
    *
    * This method should be called after any changes are made to a given user's
    * multi-factor configuration.
    *
    * @return void
    * @task factors
    */
   public function updateMultiFactorEnrollment() {
     $factors = id(new PhabricatorAuthFactorConfig())->loadAllWhere(
       'userPHID = %s',
       $this->getPHID());
 
     $enrolled = count($factors) ? 1 : 0;
     if ($enrolled !== $this->isEnrolledInMultiFactor) {
       $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
         queryfx(
           $this->establishConnection('w'),
           'UPDATE %T SET isEnrolledInMultiFactor = %d WHERE id = %d',
           $this->getTableName(),
           $enrolled,
           $this->getID());
       unset($unguarded);
 
       $this->isEnrolledInMultiFactor = $enrolled;
     }
   }
 
 
   /**
    * Check if the user is enrolled in multi-factor authentication.
    *
    * Enrolled users have one or more multi-factor authentication sources
    * attached to their account. For performance, this value is cached. You
    * can use @{method:updateMultiFactorEnrollment} to update the cache.
    *
    * @return bool True if the user is enrolled.
    * @task factors
    */
   public function getIsEnrolledInMultiFactor() {
     return $this->isEnrolledInMultiFactor;
   }
 
 
 /* -(  Omnipotence  )-------------------------------------------------------- */
 
 
   /**
    * Returns true if this user is omnipotent. Omnipotent users bypass all policy
    * checks.
    *
    * @return bool True if the user bypasses policy checks.
    */
   public function isOmnipotent() {
     return $this->omnipotent;
   }
 
 
   /**
    * Get an omnipotent user object for use in contexts where there is no acting
    * user, notably daemons.
    *
    * @return PhabricatorUser An omnipotent user.
    */
   public static function getOmnipotentUser() {
     static $user = null;
     if (!$user) {
       $user = new PhabricatorUser();
       $user->omnipotent = true;
       $user->makeEphemeral();
     }
     return $user;
   }
 
 
 /* -(  Managing Handles  )--------------------------------------------------- */
 
 
   /**
    * Get a @{class:PhabricatorHandleList} which benefits from this viewer's
    * internal handle pool.
    *
    * @param list<phid> List of PHIDs to load.
    * @return PhabricatorHandleList Handle list object.
    * @task handle
    */
   public function loadHandles(array $phids) {
     if ($this->handlePool === null) {
       $this->handlePool = id(new PhabricatorHandlePool())
         ->setViewer($this);
     }
 
     return $this->handlePool->newHandleList($phids);
   }
 
 
   /**
    * Get a @{class:PHUIHandleView} for a single handle.
    *
    * This benefits from the viewer's internal handle pool.
    *
    * @param phid PHID to render a handle for.
    * @return PHUIHandleView View of the handle.
    * @task handle
    */
   public function renderHandle($phid) {
     return $this->loadHandles(array($phid))->renderHandle($phid);
   }
 
 
   /**
    * Get a @{class:PHUIHandleListView} for a list of handles.
    *
    * This benefits from the viewer's internal handle pool.
    *
    * @param list<phid> List of PHIDs to render.
    * @return PHUIHandleListView View of the handles.
    * @task handle
    */
   public function renderHandleList(array $phids) {
     return $this->loadHandles($phids)->renderList();
   }
 
 
 /* -(  PhabricatorPolicyInterface  )----------------------------------------- */
 
 
   public function getCapabilities() {
     return array(
       PhabricatorPolicyCapability::CAN_VIEW,
       PhabricatorPolicyCapability::CAN_EDIT,
     );
   }
 
   public function getPolicy($capability) {
     switch ($capability) {
       case PhabricatorPolicyCapability::CAN_VIEW:
         return PhabricatorPolicies::POLICY_PUBLIC;
       case PhabricatorPolicyCapability::CAN_EDIT:
         if ($this->getIsSystemAgent() || $this->getIsMailingList()) {
           return PhabricatorPolicies::POLICY_ADMIN;
         } else {
           return PhabricatorPolicies::POLICY_NOONE;
         }
     }
   }
 
   public function hasAutomaticCapability($capability, PhabricatorUser $viewer) {
     return $this->getPHID() && ($viewer->getPHID() === $this->getPHID());
   }
 
   public function describeAutomaticCapability($capability) {
     switch ($capability) {
       case PhabricatorPolicyCapability::CAN_EDIT:
         return pht('Only you can edit your information.');
       default:
         return null;
     }
   }
 
 
 /* -(  PhabricatorCustomFieldInterface  )------------------------------------ */
 
 
   public function getCustomFieldSpecificationForRole($role) {
     return PhabricatorEnv::getEnvConfig('user.fields');
   }
 
   public function getCustomFieldBaseClass() {
     return 'PhabricatorUserCustomField';
   }
 
   public function getCustomFields() {
     return $this->assertAttached($this->customFields);
   }
 
   public function attachCustomFields(PhabricatorCustomFieldAttachment $fields) {
     $this->customFields = $fields;
     return $this;
   }
 
 
 /* -(  PhabricatorDestructibleInterface  )----------------------------------- */
 
 
   public function destroyObjectPermanently(
     PhabricatorDestructionEngine $engine) {
 
     $this->openTransaction();
       $this->delete();
 
       $externals = id(new PhabricatorExternalAccount())->loadAllWhere(
         'userPHID = %s',
         $this->getPHID());
       foreach ($externals as $external) {
         $external->delete();
       }
 
       $prefs = id(new PhabricatorUserPreferences())->loadAllWhere(
         'userPHID = %s',
         $this->getPHID());
       foreach ($prefs as $pref) {
         $pref->delete();
       }
 
       $profiles = id(new PhabricatorUserProfile())->loadAllWhere(
         'userPHID = %s',
         $this->getPHID());
       foreach ($profiles as $profile) {
         $profile->delete();
       }
 
       $keys = id(new PhabricatorAuthSSHKey())->loadAllWhere(
         'objectPHID = %s',
         $this->getPHID());
       foreach ($keys as $key) {
         $key->delete();
       }
 
       $emails = id(new PhabricatorUserEmail())->loadAllWhere(
         'userPHID = %s',
         $this->getPHID());
       foreach ($emails as $email) {
         $email->delete();
       }
 
       $sessions = id(new PhabricatorAuthSession())->loadAllWhere(
         'userPHID = %s',
         $this->getPHID());
       foreach ($sessions as $session) {
         $session->delete();
       }
 
       $factors = id(new PhabricatorAuthFactorConfig())->loadAllWhere(
         'userPHID = %s',
         $this->getPHID());
       foreach ($factors as $factor) {
         $factor->delete();
       }
 
     $this->saveTransaction();
   }
 
 
 /* -(  PhabricatorSSHPublicKeyInterface  )----------------------------------- */
 
 
   public function getSSHPublicKeyManagementURI(PhabricatorUser $viewer) {
     if ($viewer->getPHID() == $this->getPHID()) {
       // If the viewer is managing their own keys, take them to the normal
       // panel.
       return '/settings/panel/ssh/';
     } else {
       // Otherwise, take them to the administrative panel for this user.
       return '/settings/'.$this->getID().'/panel/ssh/';
     }
   }
 
   public function getSSHKeyDefaultName() {
     return 'id_rsa_phabricator';
   }
 
 
 /* -(  PhabricatorApplicationTransactionInterface  )------------------------- */
 
 
   public function getApplicationTransactionEditor() {
     return new PhabricatorUserProfileEditor();
   }
 
   public function getApplicationTransactionObject() {
     return $this;
   }
 
   public function getApplicationTransactionTemplate() {
     return new PhabricatorUserTransaction();
   }
 
   public function willRenderTimeline(
     PhabricatorApplicationTransactionView $timeline,
     AphrontRequest $request) {
     return $timeline;
   }
 
 }
diff --git a/src/applications/spaces/query/PhabricatorSpacesNamespaceQuery.php b/src/applications/spaces/query/PhabricatorSpacesNamespaceQuery.php
index ac02c306e7..77cb8aee5e 100644
--- a/src/applications/spaces/query/PhabricatorSpacesNamespaceQuery.php
+++ b/src/applications/spaces/query/PhabricatorSpacesNamespaceQuery.php
@@ -1,177 +1,188 @@
 <?php
 
 final class PhabricatorSpacesNamespaceQuery
   extends PhabricatorCursorPagedPolicyAwareQuery {
 
   const KEY_ALL = 'spaces.all';
   const KEY_DEFAULT = 'spaces.default';
 
   private $ids;
   private $phids;
   private $isDefaultNamespace;
 
   public function withIDs(array $ids) {
     $this->ids = $ids;
     return $this;
   }
 
   public function withPHIDs(array $phids) {
     $this->phids = $phids;
     return $this;
   }
 
   public function withIsDefaultNamespace($default) {
     $this->isDefaultNamespace = $default;
     return $this;
   }
 
   public function getQueryApplicationClass() {
     return 'PhabricatorSpacesApplication';
   }
 
   protected function loadPage() {
     $table = new PhabricatorSpacesNamespace();
     $conn_r = $table->establishConnection('r');
 
     $rows = queryfx_all(
       $conn_r,
       'SELECT * FROM %T %Q %Q %Q',
       $table->getTableName(),
       $this->buildWhereClause($conn_r),
       $this->buildOrderClause($conn_r),
       $this->buildLimitClause($conn_r));
 
     return $table->loadAllFromArray($rows);
   }
 
   protected function buildWhereClause(AphrontDatabaseConnection $conn_r) {
     $where = array();
 
     if ($this->ids !== null) {
       $where[] = qsprintf(
         $conn_r,
         'id IN (%Ld)',
         $this->ids);
     }
 
     if ($this->phids !== null) {
       $where[] = qsprintf(
         $conn_r,
         'phid IN (%Ls)',
         $this->phids);
     }
 
     if ($this->isDefaultNamespace !== null) {
       if ($this->isDefaultNamespace) {
         $where[] = qsprintf(
           $conn_r,
           'isDefaultNamespace = 1');
       } else {
         $where[] = qsprintf(
           $conn_r,
           'isDefaultNamespace IS NULL');
       }
     }
 
     $where[] = $this->buildPagingClause($conn_r);
     return $this->formatWhereClause($where);
   }
 
   public static function destroySpacesCache() {
     $cache = PhabricatorCaches::getRequestCache();
     $cache->deleteKeys(
       array(
         self::KEY_ALL,
         self::KEY_DEFAULT,
       ));
   }
 
   public static function getSpacesExist() {
     return (bool)self::getAllSpaces();
   }
 
+  public static function getViewerSpacesExist(PhabricatorUser $viewer) {
+    if (!self::getSpacesExist()) {
+      return false;
+    }
+
+    // If the viewer has access to only one space, pretend spaces simply don't
+    // exist.
+    $spaces = self::getViewerSpaces($viewer);
+    return (count($spaces) > 1);
+  }
+
   public static function getAllSpaces() {
     $cache = PhabricatorCaches::getRequestCache();
     $cache_key = self::KEY_ALL;
 
     $spaces = $cache->getKey($cache_key);
     if ($spaces === null) {
       $spaces = id(new PhabricatorSpacesNamespaceQuery())
         ->setViewer(PhabricatorUser::getOmnipotentUser())
         ->execute();
       $spaces = mpull($spaces, null, 'getPHID');
       $cache->setKey($cache_key, $spaces);
     }
 
     return $spaces;
   }
 
   public static function getDefaultSpace() {
     $cache = PhabricatorCaches::getRequestCache();
     $cache_key = self::KEY_DEFAULT;
 
     $default_space = $cache->getKey($cache_key, false);
     if ($default_space === false) {
       $default_space = null;
 
       $spaces = self::getAllSpaces();
       foreach ($spaces as $space) {
         if ($space->getIsDefaultNamespace()) {
           $default_space = $space;
           break;
         }
       }
 
       $cache->setKey($cache_key, $default_space);
     }
 
     return $default_space;
   }
 
   public static function getViewerSpaces(PhabricatorUser $viewer) {
     $spaces = self::getAllSpaces();
 
     $result = array();
     foreach ($spaces as $key => $space) {
       $can_see = PhabricatorPolicyFilter::hasCapability(
         $viewer,
         $space,
         PhabricatorPolicyCapability::CAN_VIEW);
       if ($can_see) {
         $result[$key] = $space;
       }
     }
 
     return $result;
   }
 
   /**
    * Get the Space PHID for an object, if one exists.
    *
    * This is intended to simplify performing a bunch of redundant checks; you
    * can intentionally pass any value in (including `null`).
    *
    * @param wild
    * @return phid|null
    */
   public static function getObjectSpacePHID($object) {
     if (!$object) {
       return null;
     }
 
     if (!($object instanceof PhabricatorSpacesInterface)) {
       return null;
     }
 
     $space_phid = $object->getSpacePHID();
     if ($space_phid === null) {
       $default_space = self::getDefaultSpace();
       if ($default_space) {
         $space_phid = $default_space->getPHID();
       }
     }
 
     return $space_phid;
   }
 
 }
diff --git a/src/applications/spaces/view/PHUISpacesNamespaceContextView.php b/src/applications/spaces/view/PHUISpacesNamespaceContextView.php
index ed28f53349..d63ae8e6f4 100644
--- a/src/applications/spaces/view/PHUISpacesNamespaceContextView.php
+++ b/src/applications/spaces/view/PHUISpacesNamespaceContextView.php
@@ -1,36 +1,49 @@
 <?php
 
 final class PHUISpacesNamespaceContextView extends AphrontView {
 
   private $object;
 
   public function setObject($object) {
     $this->object = $object;
     return $this;
   }
 
   public function getObject() {
     return $this->object;
   }
 
   public function render() {
     $object = $this->getObject();
 
     $space_phid = PhabricatorSpacesNamespaceQuery::getObjectSpacePHID($object);
     if (!$space_phid) {
       return null;
     }
 
+    // If the viewer can't see spaces, pretend they don't exist.
     $viewer = $this->getUser();
+    if (!PhabricatorSpacesNamespaceQuery::getViewerSpacesExist($viewer)) {
+      return null;
+    }
+
+    // If this is the default space, don't show a space label.
+    $default = PhabricatorSpacesNamespaceQuery::getDefaultSpace();
+    if ($default) {
+      if ($default->getPHID() == $space_phid) {
+        return null;
+      }
+    }
+
     return phutil_tag(
       'span',
       array(
         'class' => 'spaces-name',
       ),
       array(
         $viewer->renderHandle($space_phid),
         ' | ',
       ));
   }
 
 }
diff --git a/src/applications/spaces/view/PhabricatorSpacesControl.php b/src/applications/spaces/view/PhabricatorSpacesControl.php
deleted file mode 100644
index aa40238c56..0000000000
--- a/src/applications/spaces/view/PhabricatorSpacesControl.php
+++ /dev/null
@@ -1,49 +0,0 @@
-<?php
-
-final class PhabricatorSpacesControl extends AphrontFormControl {
-
-  private $object;
-
-  protected function shouldRender() {
-    // Render this control only if some Spaces exist.
-    return PhabricatorSpacesNamespaceQuery::getAllSpaces();
-  }
-
-  public function setObject(PhabricatorSpacesInterface $object) {
-    $this->object = $object;
-    return $this;
-  }
-
-  protected function getCustomControlClass() {
-    return '';
-  }
-
-  protected function getOptions() {
-    $viewer = $this->getUser();
-    $viewer_spaces = PhabricatorSpacesNamespaceQuery::getViewerSpaces($viewer);
-
-    $map = mpull($viewer_spaces, 'getNamespaceName', 'getPHID');
-    asort($map);
-
-    return $map;
-  }
-
-  protected function renderInput() {
-    $viewer = $this->getUser();
-
-    $this->setLabel(pht('Space'));
-
-    $value = $this->getValue();
-    if ($value === null) {
-      $value = $viewer->getDefaultSpacePHID();
-    }
-
-    return AphrontFormSelectControl::renderSelectTag(
-      $value,
-      $this->getOptions(),
-      array(
-        'name' => $this->getName(),
-      ));
-  }
-
-}
diff --git a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
index d89c782900..9602ee6227 100644
--- a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
+++ b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
@@ -1,3063 +1,3078 @@
 <?php
 
 /**
  *
  * Publishing and Managing State
  * ======
  *
  * After applying changes, the Editor queues a worker to publish mail, feed,
  * and notifications, and to perform other background work like updating search
  * indexes. This allows it to do this work without impacting performance for
  * users.
  *
  * When work is moved to the daemons, the Editor state is serialized by
  * @{method:getWorkerState}, then reloaded in a daemon process by
  * @{method:loadWorkerState}. **This is fragile.**
  *
  * State is not persisted into the daemons by default, because we can not send
  * arbitrary objects into the queue. This means the default behavior of any
  * state properties is to reset to their defaults without warning prior to
  * publishing.
  *
  * The easiest way to avoid this is to keep Editors stateless: the overwhelming
  * majority of Editors can be written statelessly. If you need to maintain
  * state, you can either:
  *
  *   - not require state to exist during publishing; or
  *   - pass state to the daemons by implementing @{method:getCustomWorkerState}
  *     and @{method:loadCustomWorkerState}.
  *
  * This architecture isn't ideal, and we may eventually split this class into
  * "Editor" and "Publisher" parts to make it more robust. See T6367 for some
  * discussion and context.
  *
  * @task mail Sending Mail
  * @task feed Publishing Feed Stories
  * @task search Search Index
  * @task files Integration with Files
  * @task workers Managing Workers
  */
 abstract class PhabricatorApplicationTransactionEditor
   extends PhabricatorEditor {
 
   private $contentSource;
   private $object;
   private $xactions;
 
   private $isNewObject;
   private $mentionedPHIDs;
   private $continueOnNoEffect;
   private $continueOnMissingFields;
   private $parentMessageID;
   private $heraldAdapter;
   private $heraldTranscript;
   private $subscribers;
   private $unmentionablePHIDMap = array();
   private $applicationEmail;
 
   private $isPreview;
   private $isHeraldEditor;
   private $isInverseEdgeEditor;
   private $actingAsPHID;
   private $disableEmail;
 
   private $heraldEmailPHIDs = array();
   private $heraldForcedEmailPHIDs = array();
   private $heraldHeader;
   private $mailToPHIDs = array();
   private $mailCCPHIDs = array();
   private $feedNotifyPHIDs = array();
   private $feedRelatedPHIDs = array();
 
   /**
    * Get the class name for the application this editor is a part of.
    *
    * Uninstalling the application will disable the editor.
    *
    * @return string Editor's application class name.
    */
   abstract public function getEditorApplicationClass();
 
 
   /**
    * Get a description of the objects this editor edits, like "Differential
    * Revisions".
    *
    * @return string Human readable description of edited objects.
    */
   abstract public function getEditorObjectsDescription();
 
 
   public function setActingAsPHID($acting_as_phid) {
     $this->actingAsPHID = $acting_as_phid;
     return $this;
   }
 
   public function getActingAsPHID() {
     if ($this->actingAsPHID) {
       return $this->actingAsPHID;
     }
     return $this->getActor()->getPHID();
   }
 
 
   /**
    * When the editor tries to apply transactions that have no effect, should
    * it raise an exception (default) or drop them and continue?
    *
    * Generally, you will set this flag for edits coming from "Edit" interfaces,
    * and leave it cleared for edits coming from "Comment" interfaces, so the
    * user will get a useful error if they try to submit a comment that does
    * nothing (e.g., empty comment with a status change that has already been
    * performed by another user).
    *
    * @param bool  True to drop transactions without effect and continue.
    * @return this
    */
   public function setContinueOnNoEffect($continue) {
     $this->continueOnNoEffect = $continue;
     return $this;
   }
 
   public function getContinueOnNoEffect() {
     return $this->continueOnNoEffect;
   }
 
 
   /**
    * When the editor tries to apply transactions which don't populate all of
    * an object's required fields, should it raise an exception (default) or
    * drop them and continue?
    *
    * For example, if a user adds a new required custom field (like "Severity")
    * to a task, all existing tasks won't have it populated. When users
    * manually edit existing tasks, it's usually desirable to have them provide
    * a severity. However, other operations (like batch editing just the
    * owner of a task) will fail by default.
    *
    * By setting this flag for edit operations which apply to specific fields
    * (like the priority, batch, and merge editors in Maniphest), these
    * operations can continue to function even if an object is outdated.
    *
    * @param bool  True to continue when transactions don't completely satisfy
    *              all required fields.
    * @return this
    */
   public function setContinueOnMissingFields($continue_on_missing_fields) {
     $this->continueOnMissingFields = $continue_on_missing_fields;
     return $this;
   }
 
   public function getContinueOnMissingFields() {
     return $this->continueOnMissingFields;
   }
 
 
   /**
    * Not strictly necessary, but reply handlers ideally set this value to
    * make email threading work better.
    */
   public function setParentMessageID($parent_message_id) {
     $this->parentMessageID = $parent_message_id;
     return $this;
   }
   public function getParentMessageID() {
     return $this->parentMessageID;
   }
 
   public function getIsNewObject() {
     return $this->isNewObject;
   }
 
   protected function getMentionedPHIDs() {
     return $this->mentionedPHIDs;
   }
 
   public function setIsPreview($is_preview) {
     $this->isPreview = $is_preview;
     return $this;
   }
 
   public function getIsPreview() {
     return $this->isPreview;
   }
 
   public function setIsInverseEdgeEditor($is_inverse_edge_editor) {
     $this->isInverseEdgeEditor = $is_inverse_edge_editor;
     return $this;
   }
 
   public function getIsInverseEdgeEditor() {
     return $this->isInverseEdgeEditor;
   }
 
   public function setIsHeraldEditor($is_herald_editor) {
     $this->isHeraldEditor = $is_herald_editor;
     return $this;
   }
 
   public function getIsHeraldEditor() {
     return $this->isHeraldEditor;
   }
 
   /**
    * Prevent this editor from generating email when applying transactions.
    *
    * @param bool  True to disable email.
    * @return this
    */
   public function setDisableEmail($disable_email) {
     $this->disableEmail = $disable_email;
     return $this;
   }
 
   public function getDisableEmail() {
     return $this->disableEmail;
   }
 
   public function setUnmentionablePHIDMap(array $map) {
     $this->unmentionablePHIDMap = $map;
     return $this;
   }
 
   public function getUnmentionablePHIDMap() {
     return $this->unmentionablePHIDMap;
   }
 
   protected function shouldEnableMentions(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return true;
   }
 
   public function setApplicationEmail(
     PhabricatorMetaMTAApplicationEmail $email) {
     $this->applicationEmail = $email;
     return $this;
   }
 
   public function getApplicationEmail() {
     return $this->applicationEmail;
   }
 
   public function getTransactionTypes() {
     $types = array();
 
     if ($this->object instanceof PhabricatorSubscribableInterface) {
       $types[] = PhabricatorTransactions::TYPE_SUBSCRIBERS;
     }
 
     if ($this->object instanceof PhabricatorCustomFieldInterface) {
       $types[] = PhabricatorTransactions::TYPE_CUSTOMFIELD;
     }
 
     if ($this->object instanceof HarbormasterBuildableInterface) {
       $types[] = PhabricatorTransactions::TYPE_BUILDABLE;
     }
 
     if ($this->object instanceof PhabricatorTokenReceiverInterface) {
       $types[] = PhabricatorTransactions::TYPE_TOKEN;
     }
 
     if ($this->object instanceof PhabricatorProjectInterface ||
         $this->object instanceof PhabricatorMentionableInterface) {
       $types[] = PhabricatorTransactions::TYPE_EDGE;
     }
 
     if ($this->object instanceof PhabricatorSpacesInterface) {
       $types[] = PhabricatorTransactions::TYPE_SPACE;
     }
 
     return $types;
   }
 
   private function adjustTransactionValues(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     if ($xaction->shouldGenerateOldValue()) {
       $old = $this->getTransactionOldValue($object, $xaction);
       $xaction->setOldValue($old);
     }
 
     $new = $this->getTransactionNewValue($object, $xaction);
     $xaction->setNewValue($new);
   }
 
   private function getTransactionOldValue(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         return array_values($this->subscribers);
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
         return $object->getViewPolicy();
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
         return $object->getEditPolicy();
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
         return $object->getJoinPolicy();
       case PhabricatorTransactions::TYPE_SPACE:
         $space_phid = $object->getSpacePHID();
         if ($space_phid === null) {
           if ($this->getIsNewObject()) {
             // In this case, just return `null` so we know this is the initial
             // transaction and it should be hidden.
             return null;
           }
 
           $default_space = PhabricatorSpacesNamespaceQuery::getDefaultSpace();
           if ($default_space) {
             $space_phid = $default_space->getPHID();
           }
         }
         return $space_phid;
       case PhabricatorTransactions::TYPE_EDGE:
         $edge_type = $xaction->getMetadataValue('edge:type');
         if (!$edge_type) {
           throw new Exception(
             pht(
               "Edge transaction has no '%s'!",
               'edge:type'));
         }
 
         $old_edges = array();
         if ($object->getPHID()) {
           $edge_src = $object->getPHID();
 
           $old_edges = id(new PhabricatorEdgeQuery())
             ->withSourcePHIDs(array($edge_src))
             ->withEdgeTypes(array($edge_type))
             ->needEdgeData(true)
             ->execute();
 
           $old_edges = $old_edges[$edge_src][$edge_type];
         }
         return $old_edges;
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         // NOTE: Custom fields have their old value pre-populated when they are
         // built by PhabricatorCustomFieldList.
         return $xaction->getOldValue();
       case PhabricatorTransactions::TYPE_COMMENT:
         return null;
       default:
         return $this->getCustomTransactionOldValue($object, $xaction);
     }
   }
 
   private function getTransactionNewValue(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         return $this->getPHIDTransactionNewValue($xaction);
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
       case PhabricatorTransactions::TYPE_BUILDABLE:
       case PhabricatorTransactions::TYPE_TOKEN:
       case PhabricatorTransactions::TYPE_INLINESTATE:
         return $xaction->getNewValue();
       case PhabricatorTransactions::TYPE_SPACE:
         $space_phid = $xaction->getNewValue();
         if (!strlen($space_phid)) {
-          // If an install has no Spaces, we might end up with the empty string
-          // here instead of a strict `null`. Just make this work like callers
-          // might reasonably expect.
-          return null;
+          // If an install has no Spaces or the Spaces controls are not visible
+          // to the viewer, we might end up with the empty string here instead
+          // of a strict `null`, because some controller just used `getStr()`
+          // to read the space PHID from the request.
+          // Just make this work like callers might reasonably expect so we
+          // don't need to handle this specially in every EditController.
+          return $this->getActor()->getDefaultSpacePHID();
         } else {
           return $space_phid;
         }
       case PhabricatorTransactions::TYPE_EDGE:
         return $this->getEdgeTransactionNewValue($xaction);
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getCustomFieldForTransaction($object, $xaction);
         return $field->getNewValueFromApplicationTransactions($xaction);
       case PhabricatorTransactions::TYPE_COMMENT:
         return null;
       default:
         return $this->getCustomTransactionNewValue($object, $xaction);
     }
   }
 
   protected function getCustomTransactionOldValue(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     throw new Exception(pht('Capability not supported!'));
   }
 
   protected function getCustomTransactionNewValue(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     throw new Exception(pht('Capability not supported!'));
   }
 
   protected function transactionHasEffect(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_COMMENT:
         return $xaction->hasComment();
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getCustomFieldForTransaction($object, $xaction);
         return $field->getApplicationTransactionHasEffect($xaction);
       case PhabricatorTransactions::TYPE_EDGE:
         // A straight value comparison here doesn't always get the right
         // result, because newly added edges aren't fully populated. Instead,
         // compare the changes in a more granular way.
         $old = $xaction->getOldValue();
         $new = $xaction->getNewValue();
 
         $old_dst = array_keys($old);
         $new_dst = array_keys($new);
 
         // NOTE: For now, we don't consider edge reordering to be a change.
         // We have very few order-dependent edges and effectively no order
         // oriented UI. This might change in the future.
         sort($old_dst);
         sort($new_dst);
 
         if ($old_dst !== $new_dst) {
           // We've added or removed edges, so this transaction definitely
           // has an effect.
           return true;
         }
 
         // We haven't added or removed edges, but we might have changed
         // edge data.
         foreach ($old as $key => $old_value) {
           $new_value = $new[$key];
           if ($old_value['data'] !== $new_value['data']) {
             return true;
           }
         }
 
         return false;
     }
 
     return ($xaction->getOldValue() !== $xaction->getNewValue());
   }
 
   protected function shouldApplyInitialEffects(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return false;
   }
 
   protected function applyInitialEffects(
     PhabricatorLiskDAO $object,
     array $xactions) {
     throw new PhutilMethodNotImplementedException();
   }
 
   private function applyInternalEffects(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getCustomFieldForTransaction($object, $xaction);
         return $field->applyApplicationTransactionInternalEffects($xaction);
       case PhabricatorTransactions::TYPE_BUILDABLE:
       case PhabricatorTransactions::TYPE_TOKEN:
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
       case PhabricatorTransactions::TYPE_INLINESTATE:
       case PhabricatorTransactions::TYPE_EDGE:
       case PhabricatorTransactions::TYPE_SPACE:
       case PhabricatorTransactions::TYPE_COMMENT:
         return $this->applyBuiltinInternalTransaction($object, $xaction);
     }
 
     return $this->applyCustomInternalTransaction($object, $xaction);
   }
 
   private function applyExternalEffects(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         $subeditor = id(new PhabricatorSubscriptionsEditor())
           ->setObject($object)
           ->setActor($this->requireActor());
 
         $old_map = array_fuse($xaction->getOldValue());
         $new_map = array_fuse($xaction->getNewValue());
 
         $subeditor->unsubscribe(
           array_keys(
             array_diff_key($old_map, $new_map)));
 
         $subeditor->subscribeExplicit(
           array_keys(
             array_diff_key($new_map, $old_map)));
 
         $subeditor->save();
 
         // for the rest of these edits, subscribers should include those just
         // added as well as those just removed.
         $subscribers = array_unique(array_merge(
           $this->subscribers,
           $xaction->getOldValue(),
           $xaction->getNewValue()));
         $this->subscribers = $subscribers;
         return $this->applyBuiltinExternalTransaction($object, $xaction);
 
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getCustomFieldForTransaction($object, $xaction);
         return $field->applyApplicationTransactionExternalEffects($xaction);
       case PhabricatorTransactions::TYPE_EDGE:
       case PhabricatorTransactions::TYPE_BUILDABLE:
       case PhabricatorTransactions::TYPE_TOKEN:
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
       case PhabricatorTransactions::TYPE_INLINESTATE:
       case PhabricatorTransactions::TYPE_SPACE:
       case PhabricatorTransactions::TYPE_COMMENT:
         return $this->applyBuiltinExternalTransaction($object, $xaction);
     }
 
     return $this->applyCustomExternalTransaction($object, $xaction);
   }
 
   protected function applyCustomInternalTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     $type = $xaction->getTransactionType();
     throw new Exception(
       pht(
         "Transaction type '%s' is missing an internal apply implementation!",
         $type));
   }
 
   protected function applyCustomExternalTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     $type = $xaction->getTransactionType();
     throw new Exception(
       pht(
         "Transaction type '%s' is missing an external apply implementation!",
         $type));
   }
 
   /**
    * @{class:PhabricatorTransactions} provides many built-in transactions
    * which should not require much - if any - code in specific applications.
    *
    * This method is a hook for the exceedingly-rare cases where you may need
    * to do **additional** work for built-in transactions. Developers should
    * extend this method, making sure to return the parent implementation
    * regardless of handling any transactions.
    *
    * See also @{method:applyBuiltinExternalTransaction}.
    */
   protected function applyBuiltinInternalTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
         $object->setViewPolicy($xaction->getNewValue());
         break;
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
         $object->setEditPolicy($xaction->getNewValue());
         break;
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
         $object->setJoinPolicy($xaction->getNewValue());
         break;
       case PhabricatorTransactions::TYPE_SPACE:
         $object->setSpacePHID($xaction->getNewValue());
         break;
     }
   }
 
   /**
    * See @{method::applyBuiltinInternalTransaction}.
    */
   protected function applyBuiltinExternalTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_EDGE:
         if ($this->getIsInverseEdgeEditor()) {
           // If we're writing an inverse edge transaction, don't actually
           // do anything. The initiating editor on the other side of the
           // transaction will take care of the edge writes.
           break;
         }
 
         $old = $xaction->getOldValue();
         $new = $xaction->getNewValue();
         $src = $object->getPHID();
         $const = $xaction->getMetadataValue('edge:type');
 
         $type = PhabricatorEdgeType::getByConstant($const);
         if ($type->shouldWriteInverseTransactions()) {
           $this->applyInverseEdgeTransactions(
             $object,
             $xaction,
             $type->getInverseEdgeConstant());
         }
 
         foreach ($new as $dst_phid => $edge) {
           $new[$dst_phid]['src'] = $src;
         }
 
         $editor = new PhabricatorEdgeEditor();
 
         foreach ($old as $dst_phid => $edge) {
           if (!empty($new[$dst_phid])) {
             if ($old[$dst_phid]['data'] === $new[$dst_phid]['data']) {
               continue;
             }
           }
           $editor->removeEdge($src, $const, $dst_phid);
         }
 
         foreach ($new as $dst_phid => $edge) {
           if (!empty($old[$dst_phid])) {
             if ($old[$dst_phid]['data'] === $new[$dst_phid]['data']) {
               continue;
             }
           }
 
           $data = array(
             'data' => $edge['data'],
           );
 
           $editor->addEdge($src, $const, $dst_phid, $data);
         }
 
         $editor->save();
         break;
     }
   }
 
   /**
    * Fill in a transaction's common values, like author and content source.
    */
   protected function populateTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     $actor = $this->getActor();
 
     // TODO: This needs to be more sophisticated once we have meta-policies.
     $xaction->setViewPolicy(PhabricatorPolicies::POLICY_PUBLIC);
 
     if ($actor->isOmnipotent()) {
       $xaction->setEditPolicy(PhabricatorPolicies::POLICY_NOONE);
     } else {
       $xaction->setEditPolicy($this->getActingAsPHID());
     }
 
     $xaction->setAuthorPHID($this->getActingAsPHID());
     $xaction->setContentSource($this->getContentSource());
     $xaction->attachViewer($actor);
     $xaction->attachObject($object);
 
     if ($object->getPHID()) {
       $xaction->setObjectPHID($object->getPHID());
     }
 
     return $xaction;
   }
 
   protected function didApplyInternalEffects(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return $xactions;
   }
 
   protected function applyFinalEffects(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return $xactions;
   }
 
   public function setContentSource(PhabricatorContentSource $content_source) {
     $this->contentSource = $content_source;
     return $this;
   }
 
   public function setContentSourceFromRequest(AphrontRequest $request) {
     return $this->setContentSource(
       PhabricatorContentSource::newFromRequest($request));
   }
 
   public function setContentSourceFromConduitRequest(
     ConduitAPIRequest $request) {
 
     $content_source = PhabricatorContentSource::newForSource(
       PhabricatorContentSource::SOURCE_CONDUIT,
       array());
 
     return $this->setContentSource($content_source);
   }
 
   public function getContentSource() {
     return $this->contentSource;
   }
 
   final public function applyTransactions(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $this->object = $object;
     $this->xactions = $xactions;
     $this->isNewObject = ($object->getPHID() === null);
 
     $this->validateEditParameters($object, $xactions);
 
     $actor = $this->requireActor();
 
     // NOTE: Some transaction expansion requires that the edited object be
     // attached.
     foreach ($xactions as $xaction) {
       $xaction->attachObject($object);
       $xaction->attachViewer($actor);
     }
 
     $xactions = $this->expandTransactions($object, $xactions);
     $xactions = $this->expandSupportTransactions($object, $xactions);
     $xactions = $this->combineTransactions($xactions);
 
     foreach ($xactions as $xaction) {
       $xaction = $this->populateTransaction($object, $xaction);
     }
 
     $is_preview = $this->getIsPreview();
     $read_locking = false;
     $transaction_open = false;
 
     if (!$is_preview) {
       $errors = array();
       $type_map = mgroup($xactions, 'getTransactionType');
       foreach ($this->getTransactionTypes() as $type) {
         $type_xactions = idx($type_map, $type, array());
         $errors[] = $this->validateTransaction($object, $type, $type_xactions);
       }
 
       $errors[] = $this->validateAllTransactions($object, $xactions);
       $errors = array_mergev($errors);
 
       $continue_on_missing = $this->getContinueOnMissingFields();
       foreach ($errors as $key => $error) {
         if ($continue_on_missing && $error->getIsMissingFieldError()) {
           unset($errors[$key]);
         }
       }
 
       if ($errors) {
         throw new PhabricatorApplicationTransactionValidationException($errors);
       }
 
       $file_phids = $this->extractFilePHIDs($object, $xactions);
 
       if ($object->getID()) {
         foreach ($xactions as $xaction) {
 
           // If any of the transactions require a read lock, hold one and
           // reload the object. We need to do this fairly early so that the
           // call to `adjustTransactionValues()` (which populates old values)
           // is based on the synchronized state of the object, which may differ
           // from the state when it was originally loaded.
 
           if ($this->shouldReadLock($object, $xaction)) {
             $object->openTransaction();
             $object->beginReadLocking();
             $transaction_open = true;
             $read_locking = true;
             $object->reload();
             break;
           }
         }
       }
 
       if ($this->shouldApplyInitialEffects($object, $xactions)) {
         if (!$transaction_open) {
           $object->openTransaction();
           $transaction_open = true;
         }
       }
     }
 
     if ($this->shouldApplyInitialEffects($object, $xactions)) {
       $this->applyInitialEffects($object, $xactions);
     }
 
     foreach ($xactions as $xaction) {
       $this->adjustTransactionValues($object, $xaction);
     }
 
     $xactions = $this->filterTransactions($object, $xactions);
 
     if (!$xactions) {
       if ($read_locking) {
         $object->endReadLocking();
         $read_locking = false;
       }
       if ($transaction_open) {
         $object->killTransaction();
         $transaction_open = false;
       }
       return array();
     }
 
     // Now that we've merged, filtered, and combined transactions, check for
     // required capabilities.
     foreach ($xactions as $xaction) {
       $this->requireCapabilities($object, $xaction);
     }
 
     $xactions = $this->sortTransactions($xactions);
 
     if ($is_preview) {
       $this->loadHandles($xactions);
       return $xactions;
     }
 
     $comment_editor = id(new PhabricatorApplicationTransactionCommentEditor())
       ->setActor($actor)
       ->setActingAsPHID($this->getActingAsPHID())
       ->setContentSource($this->getContentSource());
 
     if (!$transaction_open) {
       $object->openTransaction();
     }
 
       foreach ($xactions as $xaction) {
         $this->applyInternalEffects($object, $xaction);
       }
 
       $xactions = $this->didApplyInternalEffects($object, $xactions);
 
       try {
         $object->save();
       } catch (AphrontDuplicateKeyQueryException $ex) {
         $object->killTransaction();
         throw $ex;
       }
 
       foreach ($xactions as $xaction) {
         $xaction->setObjectPHID($object->getPHID());
         if ($xaction->getComment()) {
           $xaction->setPHID($xaction->generatePHID());
           $comment_editor->applyEdit($xaction, $xaction->getComment());
         } else {
           $xaction->save();
         }
       }
 
       if ($file_phids) {
         $this->attachFiles($object, $file_phids);
       }
 
       foreach ($xactions as $xaction) {
         $this->applyExternalEffects($object, $xaction);
       }
 
       $xactions = $this->applyFinalEffects($object, $xactions);
 
       if ($read_locking) {
         $object->endReadLocking();
         $read_locking = false;
       }
 
     $object->saveTransaction();
 
     // Now that we've completely applied the core transaction set, try to apply
     // Herald rules. Herald rules are allowed to either take direct actions on
     // the database (like writing flags), or take indirect actions (like saving
     // some targets for CC when we generate mail a little later), or return
     // transactions which we'll apply normally using another Editor.
 
     // First, check if *this* is a sub-editor which is itself applying Herald
     // rules: if it is, stop working and return so we don't descend into
     // madness.
 
     // Otherwise, we're not a Herald editor, so process Herald rules (possibly
     // using a Herald editor to apply resulting transactions) and then send out
     // mail, notifications, and feed updates about everything.
 
     if ($this->getIsHeraldEditor()) {
       // We are the Herald editor, so stop work here and return the updated
       // transactions.
       return $xactions;
     } else if ($this->getIsInverseEdgeEditor()) {
       // If we're applying inverse edge transactions, don't trigger Herald.
       // From a product perspective, the current set of inverse edges (most
       // often, mentions) aren't things users would expect to trigger Herald.
       // From a technical perspective, objects loaded by the inverse editor may
       // not have enough data to execute rules. At least for now, just stop
       // Herald from executing when applying inverse edges.
     } else if ($this->shouldApplyHeraldRules($object, $xactions)) {
       // We are not the Herald editor, so try to apply Herald rules.
       $herald_xactions = $this->applyHeraldRules($object, $xactions);
 
       if ($herald_xactions) {
         $xscript_id = $this->getHeraldTranscript()->getID();
         foreach ($herald_xactions as $herald_xaction) {
           $herald_xaction->setMetadataValue('herald:transcriptID', $xscript_id);
         }
 
         // NOTE: We're acting as the omnipotent user because rules deal with
         // their own policy issues. We use a synthetic author PHID (the
         // Herald application) as the author of record, so that transactions
         // will render in a reasonable way ("Herald assigned this task ...").
         $herald_actor = PhabricatorUser::getOmnipotentUser();
         $herald_phid = id(new PhabricatorHeraldApplication())->getPHID();
 
         // TODO: It would be nice to give transactions a more specific source
         // which points at the rule which generated them. You can figure this
         // out from transcripts, but it would be cleaner if you didn't have to.
 
         $herald_source = PhabricatorContentSource::newForSource(
           PhabricatorContentSource::SOURCE_HERALD,
           array());
 
         $herald_editor = newv(get_class($this), array())
           ->setContinueOnNoEffect(true)
           ->setContinueOnMissingFields(true)
           ->setParentMessageID($this->getParentMessageID())
           ->setIsHeraldEditor(true)
           ->setActor($herald_actor)
           ->setActingAsPHID($herald_phid)
           ->setContentSource($herald_source);
 
         $herald_xactions = $herald_editor->applyTransactions(
           $object,
           $herald_xactions);
 
         $adapter = $this->getHeraldAdapter();
         $this->heraldEmailPHIDs = $adapter->getEmailPHIDs();
         $this->heraldForcedEmailPHIDs = $adapter->getForcedEmailPHIDs();
 
         // Merge the new transactions into the transaction list: we want to
         // send email and publish feed stories about them, too.
         $xactions = array_merge($xactions, $herald_xactions);
       }
     }
 
     $this->didApplyTransactions($xactions);
 
     if ($object instanceof PhabricatorCustomFieldInterface) {
       // Maybe this makes more sense to move into the search index itself? For
       // now I'm putting it here since I think we might end up with things that
       // need it to be up to date once the next page loads, but if we don't go
       // there we we could move it into search once search moves to the daemons.
 
       // It now happens in the search indexer as well, but the search indexer is
       // always daemonized, so the logic above still potentially holds. We could
       // possibly get rid of this. The major motivation for putting it in the
       // indexer was to enable reindexing to work.
 
       $fields = PhabricatorCustomField::getObjectFields(
         $object,
         PhabricatorCustomField::ROLE_APPLICATIONSEARCH);
       $fields->readFieldsFromStorage($object);
       $fields->rebuildIndexes($object);
     }
 
     $herald_xscript = $this->getHeraldTranscript();
     if ($herald_xscript) {
       $herald_header = $herald_xscript->getXHeraldRulesHeader();
       $herald_header = HeraldTranscript::saveXHeraldRulesHeader(
         $object->getPHID(),
         $herald_header);
     } else {
       $herald_header = HeraldTranscript::loadXHeraldRulesHeader(
         $object->getPHID());
     }
     $this->heraldHeader = $herald_header;
 
     // We're going to compute some of the data we'll use to publish these
     // transactions here, before queueing a worker.
     //
     // Primarily, this is more correct: we want to publish the object as it
     // exists right now. The worker may not execute for some time, and we want
     // to use the current To/CC list, not respect any changes which may occur
     // between now and when the worker executes.
     //
     // As a secondary benefit, this tends to reduce the amount of state that
     // Editors need to pass into workers.
     $object = $this->willPublish($object, $xactions);
 
     if (!$this->getDisableEmail()) {
       if ($this->shouldSendMail($object, $xactions)) {
         $this->mailToPHIDs = $this->getMailTo($object);
         $this->mailCCPHIDs = $this->getMailCC($object);
       }
     }
 
     if ($this->shouldPublishFeedStory($object, $xactions)) {
       $this->feedRelatedPHIDs = $this->getFeedRelatedPHIDs($object, $xactions);
       $this->feedNotifyPHIDs = $this->getFeedNotifyPHIDs($object, $xactions);
     }
 
     PhabricatorWorker::scheduleTask(
       'PhabricatorApplicationTransactionPublishWorker',
       array(
         'objectPHID' => $object->getPHID(),
         'actorPHID' => $this->getActingAsPHID(),
         'xactionPHIDs' => mpull($xactions, 'getPHID'),
         'state' => $this->getWorkerState(),
       ),
       array(
         'objectPHID' => $object->getPHID(),
         'priority' => PhabricatorWorker::PRIORITY_ALERTS,
       ));
 
     return $xactions;
   }
 
   public function publishTransactions(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     // Hook for edges or other properties that may need (re-)loading
     $object = $this->willPublish($object, $xactions);
 
     $mailed = array();
     if (!$this->getDisableEmail()) {
       if ($this->shouldSendMail($object, $xactions)) {
         $mailed = $this->sendMail($object, $xactions);
       }
     }
 
     if ($this->supportsSearch()) {
       id(new PhabricatorSearchIndexer())
         ->queueDocumentForIndexing(
           $object->getPHID(),
           $this->getSearchContextParameter($object, $xactions));
     }
 
     if ($this->shouldPublishFeedStory($object, $xactions)) {
       $this->publishFeedStory(
         $object,
         $xactions,
         $mailed);
     }
 
     return $xactions;
   }
 
   protected function didApplyTransactions(array $xactions) {
     // Hook for subclasses.
     return;
   }
 
 
   /**
    * Determine if the editor should hold a read lock on the object while
    * applying a transaction.
    *
    * If the editor does not hold a lock, two editors may read an object at the
    * same time, then apply their changes without any synchronization. For most
    * transactions, this does not matter much. However, it is important for some
    * transactions. For example, if an object has a transaction count on it, both
    * editors may read the object with `count = 23`, then independently update it
    * and save the object with `count = 24` twice. This will produce the wrong
    * state: the object really has 25 transactions, but the count is only 24.
    *
    * Generally, transactions fall into one of four buckets:
    *
    *   - Append operations: Actions like adding a comment to an object purely
    *     add information to its state, and do not depend on the current object
    *     state in any way. These transactions never need to hold locks.
    *   - Overwrite operations: Actions like changing the title or description
    *     of an object replace the current value with a new value, so the end
    *     state is consistent without a lock. We currently do not lock these
    *     transactions, although we may in the future.
    *   - Edge operations: Edge and subscription operations have internal
    *     synchronization which limits the damage race conditions can cause.
    *     We do not currently lock these transactions, although we may in the
    *     future.
    *   - Update operations: Actions like incrementing a count on an object.
    *     These operations generally should use locks, unless it is not
    *     important that the state remain consistent in the presence of races.
    *
    * @param   PhabricatorLiskDAO  Object being updated.
    * @param   PhabricatorApplicationTransaction Transaction being applied.
    * @return  bool                True to synchronize the edit with a lock.
    */
   protected function shouldReadLock(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     return false;
   }
 
   private function loadHandles(array $xactions) {
     $phids = array();
     foreach ($xactions as $key => $xaction) {
       $phids[$key] = $xaction->getRequiredHandlePHIDs();
     }
     $handles = array();
     $merged = array_mergev($phids);
     if ($merged) {
       $handles = id(new PhabricatorHandleQuery())
         ->setViewer($this->requireActor())
         ->withPHIDs($merged)
         ->execute();
     }
     foreach ($xactions as $key => $xaction) {
       $xaction->setHandles(array_select_keys($handles, $phids[$key]));
     }
   }
 
   private function loadSubscribers(PhabricatorLiskDAO $object) {
     if ($object->getPHID() &&
         ($object instanceof PhabricatorSubscribableInterface)) {
       $subs = PhabricatorSubscribersQuery::loadSubscribersForPHID(
         $object->getPHID());
       $this->subscribers = array_fuse($subs);
     } else {
       $this->subscribers = array();
     }
   }
 
   private function validateEditParameters(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     if (!$this->getContentSource()) {
       throw new PhutilInvalidStateException('setContentSource');
     }
 
     // Do a bunch of sanity checks that the incoming transactions are fresh.
     // They should be unsaved and have only "transactionType" and "newValue"
     // set.
 
     $types = array_fill_keys($this->getTransactionTypes(), true);
 
     assert_instances_of($xactions, 'PhabricatorApplicationTransaction');
     foreach ($xactions as $xaction) {
       if ($xaction->getPHID() || $xaction->getID()) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht('You can not apply transactions which already have IDs/PHIDs!'));
       }
       if ($xaction->getObjectPHID()) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht(
             'You can not apply transactions which already have %s!',
             'objectPHIDs'));
       }
       if ($xaction->getAuthorPHID()) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht(
             'You can not apply transactions which already have %s!',
             'authorPHIDs'));
       }
       if ($xaction->getCommentPHID()) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht(
             'You can not apply transactions which already have %s!',
             'commentPHIDs'));
       }
       if ($xaction->getCommentVersion() !== 0) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht(
             'You can not apply transactions which already have '.
             'commentVersions!'));
       }
 
       $expect_value = !$xaction->shouldGenerateOldValue();
       $has_value = $xaction->hasOldValue();
 
       if ($expect_value && !$has_value) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht(
             'This transaction is supposed to have an %s set, but it does not!',
             'oldValue'));
       }
 
       if ($has_value && !$expect_value) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht(
             'This transaction should generate its %s automatically, '.
             'but has already had one set!',
             'oldValue'));
       }
 
       $type = $xaction->getTransactionType();
       if (empty($types[$type])) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht(
             'Transaction has type "%s", but that transaction type is not '.
             'supported by this editor (%s).',
             $type,
             get_class($this)));
       }
     }
   }
 
   protected function requireCapabilities(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     if ($this->getIsNewObject()) {
       return;
     }
 
     $actor = $this->requireActor();
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_COMMENT:
         PhabricatorPolicyFilter::requireCapability(
           $actor,
           $object,
           PhabricatorPolicyCapability::CAN_VIEW);
         break;
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
       case PhabricatorTransactions::TYPE_SPACE:
         PhabricatorPolicyFilter::requireCapability(
           $actor,
           $object,
           PhabricatorPolicyCapability::CAN_EDIT);
         break;
     }
   }
 
   private function buildSubscribeTransaction(
     PhabricatorLiskDAO $object,
     array $xactions,
     array $blocks) {
 
     if (!($object instanceof PhabricatorSubscribableInterface)) {
       return null;
     }
 
     if ($this->shouldEnableMentions($object, $xactions)) {
       $texts = array_mergev($blocks);
       $phids = PhabricatorMarkupEngine::extractPHIDsFromMentions(
         $this->getActor(),
         $texts);
     } else {
       $phids = array();
     }
 
     $this->mentionedPHIDs = $phids;
 
     if ($object->getPHID()) {
       // Don't try to subscribe already-subscribed mentions: we want to generate
       // a dialog about an action having no effect if the user explicitly adds
       // existing CCs, but not if they merely mention existing subscribers.
       $phids = array_diff($phids, $this->subscribers);
     }
 
     if ($phids) {
       $users = id(new PhabricatorPeopleQuery())
         ->setViewer($this->getActor())
         ->withPHIDs($phids)
         ->execute();
       $users = mpull($users, null, 'getPHID');
 
       foreach ($phids as $key => $phid) {
         // Do not subscribe mentioned users
         // who do not have VIEW Permissions
         if ($object instanceof PhabricatorPolicyInterface
           && !PhabricatorPolicyFilter::hasCapability(
           $users[$phid],
           $object,
           PhabricatorPolicyCapability::CAN_VIEW)
         ) {
           unset($phids[$key]);
         } else {
           if ($object->isAutomaticallySubscribed($phid)) {
             unset($phids[$key]);
           }
         }
       }
       $phids = array_values($phids);
     }
     // No else here to properly return null should we unset all subscriber
     if (!$phids) {
       return null;
     }
 
     $xaction = newv(get_class(head($xactions)), array());
     $xaction->setTransactionType(PhabricatorTransactions::TYPE_SUBSCRIBERS);
     $xaction->setNewValue(array('+' => $phids));
 
     return $xaction;
   }
 
   protected function getRemarkupBlocksFromTransaction(
     PhabricatorApplicationTransaction $transaction) {
     return $transaction->getRemarkupBlocks();
   }
 
   protected function mergeTransactions(
     PhabricatorApplicationTransaction $u,
     PhabricatorApplicationTransaction $v) {
 
     $type = $u->getTransactionType();
 
     switch ($type) {
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         return $this->mergePHIDOrEdgeTransactions($u, $v);
       case PhabricatorTransactions::TYPE_EDGE:
         $u_type = $u->getMetadataValue('edge:type');
         $v_type = $v->getMetadataValue('edge:type');
         if ($u_type == $v_type) {
           return $this->mergePHIDOrEdgeTransactions($u, $v);
         }
         return null;
     }
 
     // By default, do not merge the transactions.
     return null;
   }
 
   /**
    * Optionally expand transactions which imply other effects. For example,
    * resigning from a revision in Differential implies removing yourself as
    * a reviewer.
    */
   private function expandTransactions(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $results = array();
     foreach ($xactions as $xaction) {
       foreach ($this->expandTransaction($object, $xaction) as $expanded) {
         $results[] = $expanded;
       }
     }
 
     return $results;
   }
 
   protected function expandTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     return array($xaction);
   }
 
 
   public function getExpandedSupportTransactions(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     $xactions = array($xaction);
     $xactions = $this->expandSupportTransactions(
       $object,
       $xactions);
 
     if (count($xactions) == 1) {
       return array();
     }
 
     foreach ($xactions as $index => $cxaction) {
       if ($cxaction === $xaction) {
         unset($xactions[$index]);
         break;
       }
     }
 
     return $xactions;
   }
 
   private function expandSupportTransactions(
     PhabricatorLiskDAO $object,
     array $xactions) {
     $this->loadSubscribers($object);
 
     $xactions = $this->applyImplicitCC($object, $xactions);
 
     $blocks = array();
     foreach ($xactions as $key => $xaction) {
       $blocks[$key] = $this->getRemarkupBlocksFromTransaction($xaction);
     }
 
     $subscribe_xaction = $this->buildSubscribeTransaction(
       $object,
       $xactions,
       $blocks);
     if ($subscribe_xaction) {
       $xactions[] = $subscribe_xaction;
     }
 
     // TODO: For now, this is just a placeholder.
     $engine = PhabricatorMarkupEngine::getEngine('extract');
     $engine->setConfig('viewer', $this->requireActor());
 
     $block_xactions = $this->expandRemarkupBlockTransactions(
       $object,
       $xactions,
       $blocks,
       $engine);
 
     foreach ($block_xactions as $xaction) {
       $xactions[] = $xaction;
     }
 
     return $xactions;
   }
 
   private function expandRemarkupBlockTransactions(
     PhabricatorLiskDAO $object,
     array $xactions,
     $blocks,
     PhutilMarkupEngine $engine) {
 
     $block_xactions = $this->expandCustomRemarkupBlockTransactions(
       $object,
       $xactions,
       $blocks,
       $engine);
 
     $mentioned_phids = array();
     if ($this->shouldEnableMentions($object, $xactions)) {
       foreach ($blocks as $key => $xaction_blocks) {
         foreach ($xaction_blocks as $block) {
           $engine->markupText($block);
           $mentioned_phids += $engine->getTextMetadata(
             PhabricatorObjectRemarkupRule::KEY_MENTIONED_OBJECTS,
             array());
         }
       }
     }
 
     if (!$mentioned_phids) {
       return $block_xactions;
     }
 
     $mentioned_objects = id(new PhabricatorObjectQuery())
       ->setViewer($this->getActor())
       ->withPHIDs($mentioned_phids)
       ->execute();
 
     $mentionable_phids = array();
     if ($this->shouldEnableMentions($object, $xactions)) {
       foreach ($mentioned_objects as $mentioned_object) {
         if ($mentioned_object instanceof PhabricatorMentionableInterface) {
           $mentioned_phid = $mentioned_object->getPHID();
           if (idx($this->getUnmentionablePHIDMap(), $mentioned_phid)) {
             continue;
           }
           // don't let objects mention themselves
           if ($object->getPHID() && $mentioned_phid == $object->getPHID()) {
             continue;
           }
           $mentionable_phids[$mentioned_phid] = $mentioned_phid;
         }
       }
     }
 
     if ($mentionable_phids) {
       $edge_type = PhabricatorObjectMentionsObjectEdgeType::EDGECONST;
       $block_xactions[] = newv(get_class(head($xactions)), array())
         ->setIgnoreOnNoEffect(true)
         ->setTransactionType(PhabricatorTransactions::TYPE_EDGE)
         ->setMetadataValue('edge:type', $edge_type)
         ->setNewValue(array('+' => $mentionable_phids));
     }
 
     return $block_xactions;
   }
 
   protected function expandCustomRemarkupBlockTransactions(
     PhabricatorLiskDAO $object,
     array $xactions,
     $blocks,
     PhutilMarkupEngine $engine) {
     return array();
   }
 
 
   /**
    * Attempt to combine similar transactions into a smaller number of total
    * transactions. For example, two transactions which edit the title of an
    * object can be merged into a single edit.
    */
   private function combineTransactions(array $xactions) {
     $stray_comments = array();
 
     $result = array();
     $types = array();
     foreach ($xactions as $key => $xaction) {
       $type = $xaction->getTransactionType();
       if (isset($types[$type])) {
         foreach ($types[$type] as $other_key) {
           $merged = $this->mergeTransactions($result[$other_key], $xaction);
           if ($merged) {
             $result[$other_key] = $merged;
 
             if ($xaction->getComment() &&
                 ($xaction->getComment() !== $merged->getComment())) {
               $stray_comments[] = $xaction->getComment();
             }
 
             if ($result[$other_key]->getComment() &&
                 ($result[$other_key]->getComment() !== $merged->getComment())) {
               $stray_comments[] = $result[$other_key]->getComment();
             }
 
             // Move on to the next transaction.
             continue 2;
           }
         }
       }
       $result[$key] = $xaction;
       $types[$type][] = $key;
     }
 
     // If we merged any comments away, restore them.
     foreach ($stray_comments as $comment) {
       $xaction = newv(get_class(head($result)), array());
       $xaction->setTransactionType(PhabricatorTransactions::TYPE_COMMENT);
       $xaction->setComment($comment);
       $result[] = $xaction;
     }
 
     return array_values($result);
   }
 
   protected function mergePHIDOrEdgeTransactions(
     PhabricatorApplicationTransaction $u,
     PhabricatorApplicationTransaction $v) {
 
     $result = $u->getNewValue();
     foreach ($v->getNewValue() as $key => $value) {
       if ($u->getTransactionType() == PhabricatorTransactions::TYPE_EDGE) {
         if (empty($result[$key])) {
           $result[$key] = $value;
         } else {
           // We're merging two lists of edge adds, sets, or removes. Merge
           // them by merging individual PHIDs within them.
           $merged = $result[$key];
 
           foreach ($value as $dst => $v_spec) {
             if (empty($merged[$dst])) {
               $merged[$dst] = $v_spec;
             } else {
               // Two transactions are trying to perform the same operation on
               // the same edge. Normalize the edge data and then merge it. This
               // allows transactions to specify how data merges execute in a
               // precise way.
 
               $u_spec = $merged[$dst];
 
               if (!is_array($u_spec)) {
                 $u_spec = array('dst' => $u_spec);
               }
               if (!is_array($v_spec)) {
                 $v_spec = array('dst' => $v_spec);
               }
 
               $ux_data = idx($u_spec, 'data', array());
               $vx_data = idx($v_spec, 'data', array());
 
               $merged_data = $this->mergeEdgeData(
                 $u->getMetadataValue('edge:type'),
                 $ux_data,
                 $vx_data);
 
               $u_spec['data'] = $merged_data;
               $merged[$dst] = $u_spec;
             }
           }
 
           $result[$key] = $merged;
         }
       } else {
         $result[$key] = array_merge($value, idx($result, $key, array()));
       }
     }
     $u->setNewValue($result);
 
     // When combining an "ignore" transaction with a normal transaction, make
     // sure we don't propagate the "ignore" flag.
     if (!$v->getIgnoreOnNoEffect()) {
       $u->setIgnoreOnNoEffect(false);
     }
 
     return $u;
   }
 
   protected function mergeEdgeData($type, array $u, array $v) {
     return $v + $u;
   }
 
   protected function getPHIDTransactionNewValue(
     PhabricatorApplicationTransaction $xaction,
     $old = null) {
 
     if ($old !== null) {
       $old = array_fuse($old);
     } else {
       $old = array_fuse($xaction->getOldValue());
     }
 
     $new = $xaction->getNewValue();
     $new_add = idx($new, '+', array());
     unset($new['+']);
     $new_rem = idx($new, '-', array());
     unset($new['-']);
     $new_set = idx($new, '=', null);
     if ($new_set !== null) {
       $new_set = array_fuse($new_set);
     }
     unset($new['=']);
 
     if ($new) {
       throw new Exception(
         pht(
           "Invalid '%s' value for PHID transaction. Value should contain only ".
           "keys '%s' (add PHIDs), '%' (remove PHIDs) and '%s' (set PHIDS).",
           'new',
           '+',
           '-',
           '='));
     }
 
     $result = array();
 
     foreach ($old as $phid) {
       if ($new_set !== null && empty($new_set[$phid])) {
         continue;
       }
       $result[$phid] = $phid;
     }
 
     if ($new_set !== null) {
       foreach ($new_set as $phid) {
         $result[$phid] = $phid;
       }
     }
 
     foreach ($new_add as $phid) {
       $result[$phid] = $phid;
     }
 
     foreach ($new_rem as $phid) {
       unset($result[$phid]);
     }
 
     return array_values($result);
   }
 
   protected function getEdgeTransactionNewValue(
     PhabricatorApplicationTransaction $xaction) {
 
     $new = $xaction->getNewValue();
     $new_add = idx($new, '+', array());
     unset($new['+']);
     $new_rem = idx($new, '-', array());
     unset($new['-']);
     $new_set = idx($new, '=', null);
     unset($new['=']);
 
     if ($new) {
       throw new Exception(
         pht(
           "Invalid '%s' value for Edge transaction. Value should contain only ".
           "keys '%s' (add edges), '%s' (remove edges) and '%s' (set edges).",
           'new',
           '+',
           '-',
           '='));
     }
 
     $old = $xaction->getOldValue();
 
     $lists = array($new_set, $new_add, $new_rem);
     foreach ($lists as $list) {
       $this->checkEdgeList($list);
     }
 
     $result = array();
     foreach ($old as $dst_phid => $edge) {
       if ($new_set !== null && empty($new_set[$dst_phid])) {
         continue;
       }
       $result[$dst_phid] = $this->normalizeEdgeTransactionValue(
         $xaction,
         $edge,
         $dst_phid);
     }
 
     if ($new_set !== null) {
       foreach ($new_set as $dst_phid => $edge) {
         $result[$dst_phid] = $this->normalizeEdgeTransactionValue(
           $xaction,
           $edge,
           $dst_phid);
       }
     }
 
     foreach ($new_add as $dst_phid => $edge) {
       $result[$dst_phid] = $this->normalizeEdgeTransactionValue(
         $xaction,
         $edge,
         $dst_phid);
     }
 
     foreach ($new_rem as $dst_phid => $edge) {
       unset($result[$dst_phid]);
     }
 
     return $result;
   }
 
   private function checkEdgeList($list) {
     if (!$list) {
       return;
     }
     foreach ($list as $key => $item) {
       if (phid_get_type($key) === PhabricatorPHIDConstants::PHID_TYPE_UNKNOWN) {
         throw new Exception(
           pht(
             "Edge transactions must have destination PHIDs as in edge ".
             "lists (found key '%s').",
             $key));
       }
       if (!is_array($item) && $item !== $key) {
         throw new Exception(
           pht(
             "Edge transactions must have PHIDs or edge specs as values ".
             "(found value '%s').",
             $item));
       }
     }
   }
 
   private function normalizeEdgeTransactionValue(
     PhabricatorApplicationTransaction $xaction,
     $edge,
     $dst_phid) {
 
     if (!is_array($edge)) {
       if ($edge != $dst_phid) {
         throw new Exception(
           pht(
             'Transaction edge data must either be the edge PHID or an edge '.
             'specification dictionary.'));
       }
       $edge = array();
     } else {
       foreach ($edge as $key => $value) {
         switch ($key) {
           case 'src':
           case 'dst':
           case 'type':
           case 'data':
           case 'dateCreated':
           case 'dateModified':
           case 'seq':
           case 'dataID':
             break;
           default:
             throw new Exception(
               pht(
                 'Transaction edge specification contains unexpected key "%s".',
                 $key));
         }
       }
     }
 
     $edge['dst'] = $dst_phid;
 
     $edge_type = $xaction->getMetadataValue('edge:type');
     if (empty($edge['type'])) {
       $edge['type'] = $edge_type;
     } else {
       if ($edge['type'] != $edge_type) {
         $this_type = $edge['type'];
         throw new Exception(
           pht(
             "Edge transaction includes edge of type '%s', but ".
             "transaction is of type '%s'. Each edge transaction ".
             "must alter edges of only one type.",
             $this_type,
             $edge_type));
       }
     }
 
     if (!isset($edge['data'])) {
       $edge['data'] = array();
     }
 
     return $edge;
   }
 
   protected function sortTransactions(array $xactions) {
     $head = array();
     $tail = array();
 
     // Move bare comments to the end, so the actions precede them.
     foreach ($xactions as $xaction) {
       $type = $xaction->getTransactionType();
       if ($type == PhabricatorTransactions::TYPE_COMMENT) {
         $tail[] = $xaction;
       } else {
         $head[] = $xaction;
       }
     }
 
     return array_values(array_merge($head, $tail));
   }
 
 
   protected function filterTransactions(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $type_comment = PhabricatorTransactions::TYPE_COMMENT;
 
     $no_effect = array();
     $has_comment = false;
     $any_effect = false;
     foreach ($xactions as $key => $xaction) {
       if ($this->transactionHasEffect($object, $xaction)) {
         if ($xaction->getTransactionType() != $type_comment) {
           $any_effect = true;
         }
       } else if ($xaction->getIgnoreOnNoEffect()) {
         unset($xactions[$key]);
       } else {
         $no_effect[$key] = $xaction;
       }
       if ($xaction->hasComment()) {
         $has_comment = true;
       }
     }
 
     if (!$no_effect) {
       return $xactions;
     }
 
     if (!$this->getContinueOnNoEffect() && !$this->getIsPreview()) {
       throw new PhabricatorApplicationTransactionNoEffectException(
         $no_effect,
         $any_effect,
         $has_comment);
     }
 
     if (!$any_effect && !$has_comment) {
       // If we only have empty comment transactions, just drop them all.
       return array();
     }
 
     foreach ($no_effect as $key => $xaction) {
       if ($xaction->getComment()) {
         $xaction->setTransactionType($type_comment);
         $xaction->setOldValue(null);
         $xaction->setNewValue(null);
       } else {
         unset($xactions[$key]);
       }
     }
 
     return $xactions;
   }
 
 
   /**
    * Hook for validating transactions. This callback will be invoked for each
    * available transaction type, even if an edit does not apply any transactions
    * of that type. This allows you to raise exceptions when required fields are
    * missing, by detecting that the object has no field value and there is no
    * transaction which sets one.
    *
    * @param PhabricatorLiskDAO Object being edited.
    * @param string Transaction type to validate.
    * @param list<PhabricatorApplicationTransaction> Transactions of given type,
    *   which may be empty if the edit does not apply any transactions of the
    *   given type.
    * @return list<PhabricatorApplicationTransactionValidationError> List of
    *   validation errors.
    */
   protected function validateTransaction(
     PhabricatorLiskDAO $object,
     $type,
     array $xactions) {
 
     $errors = array();
     switch ($type) {
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
         $errors[] = $this->validatePolicyTransaction(
           $object,
           $xactions,
           $type,
           PhabricatorPolicyCapability::CAN_VIEW);
         break;
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
         $errors[] = $this->validatePolicyTransaction(
           $object,
           $xactions,
           $type,
           PhabricatorPolicyCapability::CAN_EDIT);
         break;
       case PhabricatorTransactions::TYPE_SPACE:
         $errors[] = $this->validateSpaceTransactions(
           $object,
           $xactions,
           $type);
         break;
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $groups = array();
         foreach ($xactions as $xaction) {
           $groups[$xaction->getMetadataValue('customfield:key')][] = $xaction;
         }
 
         $field_list = PhabricatorCustomField::getObjectFields(
           $object,
           PhabricatorCustomField::ROLE_EDIT);
         $field_list->setViewer($this->getActor());
 
         $role_xactions = PhabricatorCustomField::ROLE_APPLICATIONTRANSACTIONS;
         foreach ($field_list->getFields() as $field) {
           if (!$field->shouldEnableForRole($role_xactions)) {
             continue;
           }
           $errors[] = $field->validateApplicationTransactions(
             $this,
             $type,
             idx($groups, $field->getFieldKey(), array()));
         }
         break;
     }
 
     return array_mergev($errors);
   }
 
   private function validatePolicyTransaction(
     PhabricatorLiskDAO $object,
     array $xactions,
     $transaction_type,
     $capability) {
 
     $actor = $this->requireActor();
     $errors = array();
     // Note $this->xactions is necessary; $xactions is $this->xactions of
     // $transaction_type
     $policy_object = $this->adjustObjectForPolicyChecks(
       $object,
       $this->xactions);
 
     // Make sure the user isn't editing away their ability to $capability this
     // object.
     foreach ($xactions as $xaction) {
       try {
         PhabricatorPolicyFilter::requireCapabilityWithForcedPolicy(
           $actor,
           $policy_object,
           $capability,
           $xaction->getNewValue());
       } catch (PhabricatorPolicyException $ex) {
         $errors[] = new PhabricatorApplicationTransactionValidationError(
           $transaction_type,
           pht('Invalid'),
           pht(
             'You can not select this %s policy, because you would no longer '.
             'be able to %s the object.',
             $capability,
             $capability),
           $xaction);
       }
     }
 
     if ($this->getIsNewObject()) {
       if (!$xactions) {
         $has_capability = PhabricatorPolicyFilter::hasCapability(
           $actor,
           $policy_object,
           $capability);
         if (!$has_capability) {
           $errors[] = new PhabricatorApplicationTransactionValidationError(
             $transaction_type,
             pht('Invalid'),
             pht(
               'The selected %s policy excludes you. Choose a %s policy '.
               'which allows you to %s the object.',
               $capability,
               $capability,
               $capability));
         }
       }
     }
 
     return $errors;
   }
 
 
   private function validateSpaceTransactions(
     PhabricatorLiskDAO $object,
     array $xactions,
     $transaction_type) {
     $errors = array();
 
-    $all_spaces = PhabricatorSpacesNamespaceQuery::getAllSpaces();
-    $viewer_spaces = PhabricatorSpacesNamespaceQuery::getViewerSpaces(
-      $this->getActor());
+    $actor = $this->getActor();
+
+    $has_spaces = PhabricatorSpacesNamespaceQuery::getViewerSpacesExist($actor);
+    $actor_spaces = PhabricatorSpacesNamespaceQuery::getViewerSpaces($actor);
     foreach ($xactions as $xaction) {
       $space_phid = $xaction->getNewValue();
 
       if ($space_phid === null) {
-        if (!$all_spaces) {
+        if (!$has_spaces) {
           // The install doesn't have any spaces, so this is fine.
           continue;
         }
 
         // The install has some spaces, so every object needs to be put
         // in a valid space.
         $errors[] = new PhabricatorApplicationTransactionValidationError(
           $transaction_type,
           pht('Invalid'),
           pht('You must choose a space for this object.'),
           $xaction);
         continue;
       }
 
       // If the PHID isn't `null`, it needs to be a valid space that the
       // viewer can see.
-      if (empty($viewer_spaces[$space_phid])) {
+      if (empty($actor_spaces[$space_phid])) {
         $errors[] = new PhabricatorApplicationTransactionValidationError(
           $transaction_type,
           pht('Invalid'),
           pht(
             'You can not shift this object in the selected space, because '.
             'the space does not exist or you do not have access to it.'),
           $xaction);
       }
     }
 
     return $errors;
   }
 
 
   protected function adjustObjectForPolicyChecks(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
-    return clone $object;
+    $copy = clone $object;
+
+    foreach ($xactions as $xaction) {
+      switch ($xaction->getTransactionType()) {
+        case PhabricatorTransactions::TYPE_SPACE:
+          $space_phid = $this->getTransactionNewValue($object, $xaction);
+          $copy->setSpacePHID($space_phid);
+          break;
+      }
+    }
+
+    return $copy;
   }
 
   protected function validateAllTransactions(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return array();
   }
 
   /**
    * Check for a missing text field.
    *
    * A text field is missing if the object has no value and there are no
    * transactions which set a value, or if the transactions remove the value.
    * This method is intended to make implementing @{method:validateTransaction}
    * more convenient:
    *
    *   $missing = $this->validateIsEmptyTextField(
    *     $object->getName(),
    *     $xactions);
    *
    * This will return `true` if the net effect of the object and transactions
    * is an empty field.
    *
    * @param wild Current field value.
    * @param list<PhabricatorApplicationTransaction> Transactions editing the
    *          field.
    * @return bool True if the field will be an empty text field after edits.
    */
   protected function validateIsEmptyTextField($field_value, array $xactions) {
     if (strlen($field_value) && empty($xactions)) {
       return false;
     }
 
     if ($xactions && strlen(last($xactions)->getNewValue())) {
       return false;
     }
 
     return true;
   }
 
 
 /* -(  Implicit CCs  )------------------------------------------------------- */
 
 
   /**
    * When a user interacts with an object, we might want to add them to CC.
    */
   final public function applyImplicitCC(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     if (!($object instanceof PhabricatorSubscribableInterface)) {
       // If the object isn't subscribable, we can't CC them.
       return $xactions;
     }
 
     $actor_phid = $this->getActingAsPHID();
 
     $type_user = PhabricatorPeopleUserPHIDType::TYPECONST;
     if (phid_get_type($actor_phid) != $type_user) {
       // Transactions by application actors like Herald, Harbormaster and
       // Diffusion should not CC the applications.
       return $xactions;
     }
 
     if ($object->isAutomaticallySubscribed($actor_phid)) {
       // If they're auto-subscribed, don't CC them.
       return $xactions;
     }
 
     $should_cc = false;
     foreach ($xactions as $xaction) {
       if ($this->shouldImplyCC($object, $xaction)) {
         $should_cc = true;
         break;
       }
     }
 
     if (!$should_cc) {
       // Only some types of actions imply a CC (like adding a comment).
       return $xactions;
     }
 
     if ($object->getPHID()) {
       if (isset($this->subscribers[$actor_phid])) {
         // If the user is already subscribed, don't implicitly CC them.
         return $xactions;
       }
 
       $unsub = PhabricatorEdgeQuery::loadDestinationPHIDs(
         $object->getPHID(),
         PhabricatorObjectHasUnsubscriberEdgeType::EDGECONST);
       $unsub = array_fuse($unsub);
       if (isset($unsub[$actor_phid])) {
         // If the user has previously unsubscribed from this object explicitly,
         // don't implicitly CC them.
         return $xactions;
       }
     }
 
     $xaction = newv(get_class(head($xactions)), array());
     $xaction->setTransactionType(PhabricatorTransactions::TYPE_SUBSCRIBERS);
     $xaction->setNewValue(array('+' => array($actor_phid)));
 
     array_unshift($xactions, $xaction);
 
     return $xactions;
   }
 
   protected function shouldImplyCC(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     return $xaction->isCommentTransaction();
   }
 
 
 /* -(  Sending Mail  )------------------------------------------------------- */
 
 
   /**
    * @task mail
    */
   protected function shouldSendMail(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return false;
   }
 
 
   /**
    * @task mail
    */
   protected function sendMail(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $email_to = $this->mailToPHIDs;
     $email_cc = $this->mailCCPHIDs;
     $email_cc = array_merge($email_cc, $this->heraldEmailPHIDs);
 
     $targets = $this->buildReplyHandler($object)
       ->getMailTargets($email_to, $email_cc);
 
     // Set this explicitly before we start swapping out the effective actor.
     $this->setActingAsPHID($this->getActingAsPHID());
 
 
     $mailed = array();
     foreach ($targets as $target) {
       $original_actor = $this->getActor();
 
       $viewer = $target->getViewer();
       $this->setActor($viewer);
       $locale = PhabricatorEnv::beginScopedLocale($viewer->getTranslation());
 
       $caught = null;
       $mail = null;
       try {
         // Reload handles for the new viewer.
         $this->loadHandles($xactions);
 
         $mail = $this->sendMailToTarget($object, $xactions, $target);
       } catch (Exception $ex) {
         $caught = $ex;
       }
 
       $this->setActor($original_actor);
       unset($locale);
 
       if ($caught) {
         throw $ex;
       }
 
       if ($mail) {
         foreach ($mail->buildRecipientList() as $phid) {
           $mailed[$phid] = true;
         }
       }
     }
 
     return array_keys($mailed);
   }
 
   private function sendMailToTarget(
     PhabricatorLiskDAO $object,
     array $xactions,
     PhabricatorMailTarget $target) {
 
     // Check if any of the transactions are visible for this viewer. If we
     // don't have any visible transactions, don't send the mail.
 
     $any_visible = false;
     foreach ($xactions as $xaction) {
       if (!$xaction->shouldHideForMail($xactions)) {
         $any_visible = true;
         break;
       }
     }
 
     if (!$any_visible) {
       return null;
     }
 
     $mail = $this->buildMailTemplate($object);
     $body = $this->buildMailBody($object, $xactions);
 
     $mail_tags = $this->getMailTags($object, $xactions);
     $action = $this->getMailAction($object, $xactions);
 
     if (PhabricatorEnv::getEnvConfig('metamta.email-preferences')) {
       $this->addEmailPreferenceSectionToMailBody(
         $body,
         $object,
         $xactions);
     }
 
     $mail
       ->setFrom($this->getActingAsPHID())
       ->setSubjectPrefix($this->getMailSubjectPrefix())
       ->setVarySubjectPrefix('['.$action.']')
       ->setThreadID($this->getMailThreadID($object), $this->getIsNewObject())
       ->setRelatedPHID($object->getPHID())
       ->setExcludeMailRecipientPHIDs($this->getExcludeMailRecipientPHIDs())
       ->setForceHeraldMailRecipientPHIDs($this->heraldForcedEmailPHIDs)
       ->setMailTags($mail_tags)
       ->setIsBulk(true)
       ->setBody($body->render())
       ->setHTMLBody($body->renderHTML());
 
     foreach ($body->getAttachments() as $attachment) {
       $mail->addAttachment($attachment);
     }
 
     if ($this->heraldHeader) {
       $mail->addHeader('X-Herald-Rules', $this->heraldHeader);
     }
 
     if ($object instanceof PhabricatorProjectInterface) {
       $this->addMailProjectMetadata($object, $mail);
     }
 
     if ($this->getParentMessageID()) {
       $mail->setParentMessageID($this->getParentMessageID());
     }
 
     return $target->sendMail($mail);
   }
 
   private function addMailProjectMetadata(
     PhabricatorLiskDAO $object,
     PhabricatorMetaMTAMail $template) {
 
     $project_phids = PhabricatorEdgeQuery::loadDestinationPHIDs(
       $object->getPHID(),
       PhabricatorProjectObjectHasProjectEdgeType::EDGECONST);
 
     if (!$project_phids) {
       return;
     }
 
     // TODO: This viewer isn't quite right. It would be slightly better to use
     // the mail recipient, but that's not very easy given the way rendering
     // works today.
 
     $handles = id(new PhabricatorHandleQuery())
       ->setViewer($this->requireActor())
       ->withPHIDs($project_phids)
       ->execute();
 
     $project_tags = array();
     foreach ($handles as $handle) {
       if (!$handle->isComplete()) {
         continue;
       }
       $project_tags[] = '<'.$handle->getObjectName().'>';
     }
 
     if (!$project_tags) {
       return;
     }
 
     $project_tags = implode(', ', $project_tags);
     $template->addHeader('X-Phabricator-Projects', $project_tags);
   }
 
 
   protected function getMailThreadID(PhabricatorLiskDAO $object) {
     return $object->getPHID();
   }
 
 
   /**
    * @task mail
    */
   protected function getStrongestAction(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return last(msort($xactions, 'getActionStrength'));
   }
 
 
   /**
    * @task mail
    */
   protected function buildReplyHandler(PhabricatorLiskDAO $object) {
     throw new Exception(pht('Capability not supported.'));
   }
 
   /**
    * @task mail
    */
   protected function getMailSubjectPrefix() {
     throw new Exception(pht('Capability not supported.'));
   }
 
 
   /**
    * @task mail
    */
   protected function getMailTags(
     PhabricatorLiskDAO $object,
     array $xactions) {
     $tags = array();
 
     foreach ($xactions as $xaction) {
       $tags[] = $xaction->getMailTags();
     }
 
     return array_mergev($tags);
   }
 
   /**
    * @task mail
    */
   public function getMailTagsMap() {
     // TODO: We should move shared mail tags, like "comment", here.
     return array();
   }
 
 
   /**
    * @task mail
    */
   protected function getMailAction(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return $this->getStrongestAction($object, $xactions)->getActionName();
   }
 
 
   /**
    * @task mail
    */
   protected function buildMailTemplate(PhabricatorLiskDAO $object) {
     throw new Exception(pht('Capability not supported.'));
   }
 
 
   /**
    * @task mail
    */
   protected function getMailTo(PhabricatorLiskDAO $object) {
     throw new Exception(pht('Capability not supported.'));
   }
 
 
   /**
    * @task mail
    */
   protected function getMailCC(PhabricatorLiskDAO $object) {
     $phids = array();
     $has_support = false;
 
     if ($object instanceof PhabricatorSubscribableInterface) {
       $phid = $object->getPHID();
       $phids[] = PhabricatorSubscribersQuery::loadSubscribersForPHID($phid);
       $has_support = true;
     }
 
     if ($object instanceof PhabricatorProjectInterface) {
       $project_phids = PhabricatorEdgeQuery::loadDestinationPHIDs(
         $object->getPHID(),
         PhabricatorProjectObjectHasProjectEdgeType::EDGECONST);
 
       if ($project_phids) {
         $watcher_type = PhabricatorObjectHasWatcherEdgeType::EDGECONST;
 
         $query = id(new PhabricatorEdgeQuery())
           ->withSourcePHIDs($project_phids)
           ->withEdgeTypes(array($watcher_type));
         $query->execute();
 
         $watcher_phids = $query->getDestinationPHIDs();
         if ($watcher_phids) {
           // We need to do a visibility check for all the watchers, as
           // watching a project is not a guarantee that you can see objects
           // associated with it.
           $users = id(new PhabricatorPeopleQuery())
             ->setViewer($this->requireActor())
             ->withPHIDs($watcher_phids)
             ->execute();
 
           $watchers = array();
           foreach ($users as $user) {
             $can_see = PhabricatorPolicyFilter::hasCapability(
               $user,
               $object,
               PhabricatorPolicyCapability::CAN_VIEW);
             if ($can_see) {
               $watchers[] = $user->getPHID();
             }
           }
           $phids[] = $watchers;
         }
       }
 
       $has_support = true;
     }
 
     if (!$has_support) {
       throw new Exception(pht('Capability not supported.'));
     }
 
     return array_mergev($phids);
   }
 
 
   /**
    * @task mail
    */
   protected function buildMailBody(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $body = new PhabricatorMetaMTAMailBody();
     $body->setViewer($this->requireActor());
 
     $this->addHeadersAndCommentsToMailBody($body, $xactions);
     $this->addCustomFieldsToMailBody($body, $object, $xactions);
     return $body;
   }
 
 
   /**
    * @task mail
    */
   protected function addEmailPreferenceSectionToMailBody(
     PhabricatorMetaMTAMailBody $body,
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $href = PhabricatorEnv::getProductionURI(
       '/settings/panel/emailpreferences/');
     $body->addLinkSection(pht('EMAIL PREFERENCES'), $href);
   }
 
 
   /**
    * @task mail
    */
   protected function addHeadersAndCommentsToMailBody(
     PhabricatorMetaMTAMailBody $body,
     array $xactions) {
 
     $headers = array();
     $comments = array();
 
     foreach ($xactions as $xaction) {
       if ($xaction->shouldHideForMail($xactions)) {
         continue;
       }
 
       $header = $xaction->getTitleForMail();
       if ($header !== null) {
         $headers[] = $header;
       }
 
       $comment = $xaction->getBodyForMail();
       if ($comment !== null) {
         $comments[] = $comment;
       }
     }
     $body->addRawSection(implode("\n", $headers));
 
     foreach ($comments as $comment) {
       $body->addRemarkupSection($comment);
     }
   }
 
   /**
    * @task mail
    */
   protected function addCustomFieldsToMailBody(
     PhabricatorMetaMTAMailBody $body,
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     if ($object instanceof PhabricatorCustomFieldInterface) {
       $field_list = PhabricatorCustomField::getObjectFields(
         $object,
         PhabricatorCustomField::ROLE_TRANSACTIONMAIL);
       $field_list->setViewer($this->getActor());
       $field_list->readFieldsFromStorage($object);
 
       foreach ($field_list->getFields() as $field) {
         $field->updateTransactionMailBody(
           $body,
           $this,
           $xactions);
       }
     }
   }
 
 
 
 /* -(  Publishing Feed Stories  )-------------------------------------------- */
 
 
   /**
    * @task feed
    */
   protected function shouldPublishFeedStory(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return false;
   }
 
 
   /**
    * @task feed
    */
   protected function getFeedStoryType() {
     return 'PhabricatorApplicationTransactionFeedStory';
   }
 
 
   /**
    * @task feed
    */
   protected function getFeedRelatedPHIDs(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $phids = array(
       $object->getPHID(),
       $this->getActingAsPHID(),
     );
 
     if ($object instanceof PhabricatorProjectInterface) {
       $project_phids = PhabricatorEdgeQuery::loadDestinationPHIDs(
         $object->getPHID(),
         PhabricatorProjectObjectHasProjectEdgeType::EDGECONST);
       foreach ($project_phids as $project_phid) {
         $phids[] = $project_phid;
       }
     }
 
     return $phids;
   }
 
 
   /**
    * @task feed
    */
   protected function getFeedNotifyPHIDs(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     return array_unique(array_merge(
       $this->getMailTo($object),
       $this->getMailCC($object)));
   }
 
 
   /**
    * @task feed
    */
   protected function getFeedStoryData(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $xactions = msort($xactions, 'getActionStrength');
     $xactions = array_reverse($xactions);
 
     return array(
       'objectPHID'        => $object->getPHID(),
       'transactionPHIDs'  => mpull($xactions, 'getPHID'),
     );
   }
 
 
   /**
    * @task feed
    */
   protected function publishFeedStory(
     PhabricatorLiskDAO $object,
     array $xactions,
     array $mailed_phids) {
 
     $xactions = mfilter($xactions, 'shouldHideForFeed', true);
 
     if (!$xactions) {
       return;
     }
 
     $related_phids = $this->feedRelatedPHIDs;
     $subscribed_phids = $this->feedNotifyPHIDs;
 
     $story_type = $this->getFeedStoryType();
     $story_data = $this->getFeedStoryData($object, $xactions);
 
     id(new PhabricatorFeedStoryPublisher())
       ->setStoryType($story_type)
       ->setStoryData($story_data)
       ->setStoryTime(time())
       ->setStoryAuthorPHID($this->getActingAsPHID())
       ->setRelatedPHIDs($related_phids)
       ->setPrimaryObjectPHID($object->getPHID())
       ->setSubscribedPHIDs($subscribed_phids)
       ->setMailRecipientPHIDs($mailed_phids)
       ->setMailTags($this->getMailTags($object, $xactions))
       ->publish();
   }
 
 
 /* -(  Search Index  )------------------------------------------------------- */
 
 
   /**
    * @task search
    */
   protected function supportsSearch() {
     return false;
   }
 
   /**
    * @task search
    */
   protected function getSearchContextParameter(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return null;
   }
 
 
 /* -(  Herald Integration )-------------------------------------------------- */
 
 
   protected function shouldApplyHeraldRules(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return false;
   }
 
   protected function buildHeraldAdapter(
     PhabricatorLiskDAO $object,
     array $xactions) {
     throw new Exception(pht('No herald adapter specified.'));
   }
 
   private function setHeraldAdapter(HeraldAdapter $adapter) {
     $this->heraldAdapter = $adapter;
     return $this;
   }
 
   protected function getHeraldAdapter() {
     return $this->heraldAdapter;
   }
 
   private function setHeraldTranscript(HeraldTranscript $transcript) {
     $this->heraldTranscript = $transcript;
     return $this;
   }
 
   protected function getHeraldTranscript() {
     return $this->heraldTranscript;
   }
 
   private function applyHeraldRules(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $adapter = $this->buildHeraldAdapter($object, $xactions);
     $adapter->setContentSource($this->getContentSource());
     $adapter->setIsNewObject($this->getIsNewObject());
     if ($this->getApplicationEmail()) {
       $adapter->setApplicationEmail($this->getApplicationEmail());
     }
     $xscript = HeraldEngine::loadAndApplyRules($adapter);
 
     $this->setHeraldAdapter($adapter);
     $this->setHeraldTranscript($xscript);
 
     return array_merge(
       $this->didApplyHeraldRules($object, $adapter, $xscript),
       $adapter->getQueuedTransactions());
   }
 
   protected function didApplyHeraldRules(
     PhabricatorLiskDAO $object,
     HeraldAdapter $adapter,
     HeraldTranscript $transcript) {
     return array();
   }
 
 
 /* -(  Custom Fields  )------------------------------------------------------ */
 
 
   /**
    * @task customfield
    */
   private function getCustomFieldForTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     $field_key = $xaction->getMetadataValue('customfield:key');
     if (!$field_key) {
       throw new Exception(
         pht(
         "Custom field transaction has no '%s'!",
         'customfield:key'));
     }
 
     $field = PhabricatorCustomField::getObjectField(
       $object,
       PhabricatorCustomField::ROLE_APPLICATIONTRANSACTIONS,
       $field_key);
 
     if (!$field) {
       throw new Exception(
         pht(
           "Custom field transaction has invalid '%s'; field '%s' ".
           "is disabled or does not exist.",
           'customfield:key',
           $field_key));
     }
 
     if (!$field->shouldAppearInApplicationTransactions()) {
       throw new Exception(
         pht(
           "Custom field transaction '%s' does not implement ".
           "integration for %s.",
           $field_key,
           'ApplicationTransactions'));
     }
 
     $field->setViewer($this->getActor());
 
     return $field;
   }
 
 
 /* -(  Files  )-------------------------------------------------------------- */
 
 
   /**
    * Extract the PHIDs of any files which these transactions attach.
    *
    * @task files
    */
   private function extractFilePHIDs(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $blocks = array();
     foreach ($xactions as $xaction) {
       $blocks[] = $this->getRemarkupBlocksFromTransaction($xaction);
     }
     $blocks = array_mergev($blocks);
 
     $phids = array();
     if ($blocks) {
       $phids[] = PhabricatorMarkupEngine::extractFilePHIDsFromEmbeddedFiles(
         $this->getActor(),
         $blocks);
     }
 
     foreach ($xactions as $xaction) {
       $phids[] = $this->extractFilePHIDsFromCustomTransaction(
         $object,
         $xaction);
     }
 
     $phids = array_unique(array_filter(array_mergev($phids)));
     if (!$phids) {
       return array();
     }
 
     // Only let a user attach files they can actually see, since this would
     // otherwise let you access any file by attaching it to an object you have
     // view permission on.
 
     $files = id(new PhabricatorFileQuery())
       ->setViewer($this->getActor())
       ->withPHIDs($phids)
       ->execute();
 
     return mpull($files, 'getPHID');
   }
 
   /**
    * @task files
    */
   protected function extractFilePHIDsFromCustomTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     return array();
   }
 
 
   /**
    * @task files
    */
   private function attachFiles(
     PhabricatorLiskDAO $object,
     array $file_phids) {
 
     if (!$file_phids) {
       return;
     }
 
     $editor = new PhabricatorEdgeEditor();
 
     $src = $object->getPHID();
     $type = PhabricatorObjectHasFileEdgeType::EDGECONST;
     foreach ($file_phids as $dst) {
       $editor->addEdge($src, $type, $dst);
     }
 
     $editor->save();
   }
 
   private function applyInverseEdgeTransactions(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction,
     $inverse_type) {
 
     $old = $xaction->getOldValue();
     $new = $xaction->getNewValue();
 
     $add = array_keys(array_diff_key($new, $old));
     $rem = array_keys(array_diff_key($old, $new));
 
     $add = array_fuse($add);
     $rem = array_fuse($rem);
     $all = $add + $rem;
 
     $nodes = id(new PhabricatorObjectQuery())
       ->setViewer($this->requireActor())
       ->withPHIDs($all)
       ->execute();
 
     foreach ($nodes as $node) {
       if (!($node instanceof PhabricatorApplicationTransactionInterface)) {
         continue;
       }
 
       if ($node instanceof PhabricatorUser) {
         // TODO: At least for now, don't record inverse edge transactions
         // for users (for example, "alincoln joined project X"): Feed fills
         // this role instead.
         continue;
       }
 
       $editor = $node->getApplicationTransactionEditor();
       $template = $node->getApplicationTransactionTemplate();
       $target = $node->getApplicationTransactionObject();
 
       if (isset($add[$node->getPHID()])) {
         $edge_edit_type = '+';
       } else {
         $edge_edit_type = '-';
       }
 
       $template
         ->setTransactionType($xaction->getTransactionType())
         ->setMetadataValue('edge:type', $inverse_type)
         ->setNewValue(
           array(
             $edge_edit_type => array($object->getPHID() => $object->getPHID()),
           ));
 
       $editor
         ->setContinueOnNoEffect(true)
         ->setContinueOnMissingFields(true)
         ->setParentMessageID($this->getParentMessageID())
         ->setIsInverseEdgeEditor(true)
         ->setActor($this->requireActor())
         ->setActingAsPHID($this->getActingAsPHID())
         ->setContentSource($this->getContentSource());
 
       $editor->applyTransactions($target, array($template));
     }
   }
 
 
 /* -(  Workers  )------------------------------------------------------------ */
 
 
   /**
    * Load any object state which is required to publish transactions.
    *
    * This hook is invoked in the main process before we compute data related
    * to publishing transactions (like email "To" and "CC" lists), and again in
    * the worker before publishing occurs.
    *
    * @return object Publishable object.
    * @task workers
    */
   protected function willPublish(PhabricatorLiskDAO $object, array $xactions) {
     return $object;
   }
 
 
   /**
    * Convert the editor state to a serializable dictionary which can be passed
    * to a worker.
    *
    * This data will be loaded with @{method:loadWorkerState} in the worker.
    *
    * @return dict<string, wild> Serializable editor state.
    * @task workers
    */
   final private function getWorkerState() {
     $state = array();
     foreach ($this->getAutomaticStateProperties() as $property) {
       $state[$property] = $this->$property;
     }
 
     $state += array(
       'excludeMailRecipientPHIDs' => $this->getExcludeMailRecipientPHIDs(),
       'custom' => $this->getCustomWorkerState(),
     );
 
     return $state;
   }
 
 
   /**
    * Hook; return custom properties which need to be passed to workers.
    *
    * @return dict<string, wild> Custom properties.
    * @task workers
    */
   protected function getCustomWorkerState() {
     return array();
   }
 
 
   /**
    * Load editor state using a dictionary emitted by @{method:getWorkerState}.
    *
    * This method is used to load state when running worker operations.
    *
    * @param dict<string, wild> Editor state, from @{method:getWorkerState}.
    * @return this
    * @task workers
    */
   final public function loadWorkerState(array $state) {
     foreach ($this->getAutomaticStateProperties() as $property) {
       $this->$property = idx($state, $property);
     }
 
     $exclude = idx($state, 'excludeMailRecipientPHIDs', array());
     $this->setExcludeMailRecipientPHIDs($exclude);
 
     $custom = idx($state, 'custom', array());
     $this->loadCustomWorkerState($custom);
 
     return $this;
   }
 
 
   /**
    * Hook; set custom properties on the editor from data emitted by
    * @{method:getCustomWorkerState}.
    *
    * @param dict<string, wild> Custom state,
    *   from @{method:getCustomWorkerState}.
    * @return this
    * @task workers
    */
   protected function loadCustomWorkerState(array $state) {
     return $this;
   }
 
 
   /**
    * Get a list of object properties which should be automatically sent to
    * workers in the state data.
    *
    * These properties will be automatically stored and loaded by the editor in
    * the worker.
    *
    * @return list<string> List of properties.
    * @task workers
    */
   private function getAutomaticStateProperties() {
     return array(
       'parentMessageID',
       'disableEmail',
       'isNewObject',
       'heraldEmailPHIDs',
       'heraldForcedEmailPHIDs',
       'heraldHeader',
       'mailToPHIDs',
       'mailCCPHIDs',
       'feedNotifyPHIDs',
       'feedRelatedPHIDs',
     );
   }
 
 }
diff --git a/src/view/form/control/AphrontFormPolicyControl.php b/src/view/form/control/AphrontFormPolicyControl.php
index 2997969c77..45bff0900e 100644
--- a/src/view/form/control/AphrontFormPolicyControl.php
+++ b/src/view/form/control/AphrontFormPolicyControl.php
@@ -1,234 +1,291 @@
 <?php
 
 final class AphrontFormPolicyControl extends AphrontFormControl {
 
   private $object;
   private $capability;
   private $policies;
+  private $spacePHID;
 
   public function setPolicyObject(PhabricatorPolicyInterface $object) {
     $this->object = $object;
     return $this;
   }
 
   public function setPolicies(array $policies) {
     assert_instances_of($policies, 'PhabricatorPolicy');
     $this->policies = $policies;
     return $this;
   }
 
+  public function setSpacePHID($space_phid) {
+    $this->spacePHID = $space_phid;
+    return $this;
+  }
+
+  public function getSpacePHID() {
+    return $this->spacePHID;
+  }
+
   public function setCapability($capability) {
     $this->capability = $capability;
 
     $labels = array(
       PhabricatorPolicyCapability::CAN_VIEW => pht('Visible To'),
       PhabricatorPolicyCapability::CAN_EDIT => pht('Editable By'),
       PhabricatorPolicyCapability::CAN_JOIN => pht('Joinable By'),
     );
 
     if (isset($labels[$capability])) {
       $label = $labels[$capability];
     } else {
       $capobj = PhabricatorPolicyCapability::getCapabilityByKey($capability);
       if ($capobj) {
         $label = $capobj->getCapabilityName();
       } else {
         $label = pht('Capability "%s"', $capability);
       }
     }
 
     $this->setLabel($label);
 
     return $this;
   }
 
   protected function getCustomControlClass() {
     return 'aphront-form-control-policy';
   }
 
   protected function getOptions() {
     $capability = $this->capability;
 
     $options = array();
     foreach ($this->policies as $policy) {
       if ($policy->getPHID() == PhabricatorPolicies::POLICY_PUBLIC) {
         // Never expose "Public" for capabilities which don't support it.
         $capobj = PhabricatorPolicyCapability::getCapabilityByKey($capability);
         if (!$capobj || !$capobj->shouldAllowPublicPolicySetting()) {
           continue;
         }
       }
       $policy_short_name = id(new PhutilUTF8StringTruncator())
         ->setMaximumGlyphs(28)
         ->truncateString($policy->getName());
 
       $options[$policy->getType()][$policy->getPHID()] = array(
         'name' => $policy_short_name,
         'full' => $policy->getName(),
         'icon' => $policy->getIcon(),
       );
     }
 
     // If we were passed several custom policy options, throw away the ones
     // which aren't the value for this capability. For example, an object might
     // have a custom view pollicy and a custom edit policy. When we render
     // the selector for "Can View", we don't want to show the "Can Edit"
     // custom policy -- if we did, the menu would look like this:
     //
     //   Custom
     //     Custom Policy
     //     Custom Policy
     //
     // ...where one is the "view" custom policy, and one is the "edit" custom
     // policy.
 
     $type_custom = PhabricatorPolicyType::TYPE_CUSTOM;
     if (!empty($options[$type_custom])) {
       $options[$type_custom] = array_select_keys(
         $options[$type_custom],
         array($this->getValue()));
     }
 
     // If there aren't any custom policies, add a placeholder policy so we
     // render a menu item. This allows the user to switch to a custom policy.
 
     if (empty($options[$type_custom])) {
       $placeholder = new PhabricatorPolicy();
       $placeholder->setName(pht('Custom Policy...'));
       $options[$type_custom][$this->getCustomPolicyPlaceholder()] = array(
         'name' => $placeholder->getName(),
         'full' => $placeholder->getName(),
         'icon' => $placeholder->getIcon(),
       );
     }
 
     $options = array_select_keys(
       $options,
       array(
         PhabricatorPolicyType::TYPE_GLOBAL,
         PhabricatorPolicyType::TYPE_USER,
         PhabricatorPolicyType::TYPE_CUSTOM,
         PhabricatorPolicyType::TYPE_PROJECT,
       ));
 
     return $options;
   }
 
   protected function renderInput() {
     if (!$this->object) {
       throw new Exception(pht('Call setPolicyObject() before rendering!'));
     }
     if (!$this->capability) {
       throw new Exception(pht('Call setCapability() before rendering!'));
     }
 
     $policy = $this->object->getPolicy($this->capability);
     if (!$policy) {
       // TODO: Make this configurable.
       $policy = PhabricatorPolicies::POLICY_USER;
     }
 
     if (!$this->getValue()) {
       $this->setValue($policy);
     }
 
     $control_id = celerity_generate_unique_node_id();
     $input_id = celerity_generate_unique_node_id();
 
     $caret = phutil_tag(
       'span',
       array(
         'class' => 'caret',
       ));
 
     $input = phutil_tag(
       'input',
       array(
         'type' => 'hidden',
         'id' => $input_id,
         'name' => $this->getName(),
         'value' => $this->getValue(),
       ));
 
     $options = $this->getOptions();
 
     $order = array();
     $labels = array();
     foreach ($options as $key => $values) {
       $order[$key] = array_keys($values);
       $labels[$key] = PhabricatorPolicyType::getPolicyTypeName($key);
     }
 
     $flat_options = array_mergev($options);
 
     $icons = array();
     foreach (igroup($flat_options, 'icon') as $icon => $ignored) {
       $icons[$icon] = id(new PHUIIconView())
         ->setIconFont($icon);
     }
 
 
     Javelin::initBehavior(
       'policy-control',
       array(
         'controlID' => $control_id,
         'inputID' => $input_id,
         'options' => $flat_options,
         'groups' => array_keys($options),
         'order' => $order,
         'icons' => $icons,
         'labels' => $labels,
         'value' => $this->getValue(),
         'capability' => $this->capability,
         'customPlaceholder' => $this->getCustomPolicyPlaceholder(),
       ));
 
     $selected = idx($flat_options, $this->getValue(), array());
     $selected_icon = idx($selected, 'icon');
     $selected_name = idx($selected, 'name');
 
+    $spaces_control = $this->buildSpacesControl();
+
     return phutil_tag(
       'div',
       array(
       ),
       array(
+        $spaces_control,
         javelin_tag(
           'a',
           array(
             'class' => 'grey button dropdown has-icon policy-control',
             'href' => '#',
             'mustcapture' => true,
             'sigil' => 'policy-control',
             'id' => $control_id,
           ),
           array(
             $caret,
             javelin_tag(
               'span',
               array(
                 'sigil' => 'policy-label',
                 'class' => 'phui-button-text',
               ),
               array(
                 idx($icons, $selected_icon),
                 $selected_name,
               )),
           )),
         $input,
       ));
 
     return AphrontFormSelectControl::renderSelectTag(
       $this->getValue(),
       $this->getOptions(),
       array(
         'name'      => $this->getName(),
         'disabled'  => $this->getDisabled() ? 'disabled' : null,
         'id'        => $this->getID(),
       ));
   }
 
   private function getCustomPolicyPlaceholder() {
     return 'custom:placeholder';
   }
 
+  private function buildSpacesControl() {
+    if ($this->capability != PhabricatorPolicyCapability::CAN_VIEW) {
+      return null;
+    }
+
+    if (!($this->object instanceof PhabricatorSpacesInterface)) {
+      return null;
+    }
+
+    $viewer = $this->getUser();
+    if (!PhabricatorSpacesNamespaceQuery::getViewerSpacesExist($viewer)) {
+      return null;
+    }
+
+    $space_phid = $this->getSpacePHID();
+    if ($space_phid === null) {
+      $space_phid = $viewer->getDefaultSpacePHID();
+    }
+
+    $select = AphrontFormSelectControl::renderSelectTag(
+      $space_phid,
+      $this->getSpaceOptions(),
+      array(
+        'name' => 'spacePHID',
+      ));
+
+    return $select;
+  }
+
+  protected function getSpaceOptions() {
+    $viewer = $this->getUser();
+    $viewer_spaces = PhabricatorSpacesNamespaceQuery::getViewerSpaces($viewer);
+
+    $map = array();
+    foreach ($viewer_spaces as $space) {
+      $map[$space->getPHID()] = pht(
+        'Space %s: %s',
+        $space->getMonogram(),
+        $space->getNamespaceName());
+    }
+    asort($map);
+
+    return $map;
+  }
 }