diff --git a/src/applications/metamta/storage/PhabricatorMetaMTAMail.php b/src/applications/metamta/storage/PhabricatorMetaMTAMail.php
index 34a761f4ae..af7007cd87 100644
--- a/src/applications/metamta/storage/PhabricatorMetaMTAMail.php
+++ b/src/applications/metamta/storage/PhabricatorMetaMTAMail.php
@@ -1,995 +1,996 @@
 <?php
 
 /**
  * @task recipients   Managing Recipients
  */
 final class PhabricatorMetaMTAMail extends PhabricatorMetaMTADAO {
 
   const STATUS_QUEUE = 'queued';
   const STATUS_SENT  = 'sent';
   const STATUS_FAIL  = 'fail';
   const STATUS_VOID  = 'void';
 
   const RETRY_DELAY   = 5;
 
   protected $parameters;
   protected $status;
   protected $message;
   protected $relatedPHID;
 
   private $recipientExpansionMap;
 
   public function __construct() {
 
     $this->status     = self::STATUS_QUEUE;
     $this->parameters = array();
 
     parent::__construct();
   }
 
   protected function getConfiguration() {
     return array(
       self::CONFIG_SERIALIZATION => array(
         'parameters'  => self::SERIALIZATION_JSON,
       ),
       self::CONFIG_COLUMN_SCHEMA => array(
         'status' => 'text32',
         'relatedPHID' => 'phid?',
 
         // T6203/NULLABILITY
         // This should just be empty if there's no body.
         'message' => 'text?',
       ),
       self::CONFIG_KEY_SCHEMA => array(
         'status' => array(
           'columns' => array('status'),
         ),
         'relatedPHID' => array(
           'columns' => array('relatedPHID'),
         ),
         'key_created' => array(
           'columns' => array('dateCreated'),
         ),
       ),
     ) + parent::getConfiguration();
   }
 
   protected function setParam($param, $value) {
     $this->parameters[$param] = $value;
     return $this;
   }
 
   protected function getParam($param, $default = null) {
     return idx($this->parameters, $param, $default);
   }
 
   /**
    * These tags are used to allow users to opt out of receiving certain types
    * of mail, like updates when a task's projects change.
    *
    * @param list<const>
    * @return this
    */
   public function setMailTags(array $tags) {
     $this->setParam('mailtags', array_unique($tags));
     return $this;
   }
 
   public function getMailTags() {
     return $this->getParam('mailtags', array());
   }
 
   /**
    * In Gmail, conversations will be broken if you reply to a thread and the
    * server sends back a response without referencing your Message-ID, even if
    * it references a Message-ID earlier in the thread. To avoid this, use the
    * parent email's message ID explicitly if it's available. This overwrites the
    * "In-Reply-To" and "References" headers we would otherwise generate. This
    * needs to be set whenever an action is triggered by an email message. See
    * T251 for more details.
    *
    * @param   string The "Message-ID" of the email which precedes this one.
    * @return  this
    */
   public function setParentMessageID($id) {
     $this->setParam('parent-message-id', $id);
     return $this;
   }
 
   public function getParentMessageID() {
     return $this->getParam('parent-message-id');
   }
 
   public function getSubject() {
     return $this->getParam('subject');
   }
 
   public function addTos(array $phids) {
     $phids = array_unique($phids);
     $this->setParam('to', $phids);
     return $this;
   }
 
   public function addRawTos(array $raw_email) {
 
     // Strip addresses down to bare emails, since the MailAdapter API currently
     // requires we pass it just the address (like `alincoln@logcabin.org`), not
     // a full string like `"Abraham Lincoln" <alincoln@logcabin.org>`.
     foreach ($raw_email as $key => $email) {
       $object = new PhutilEmailAddress($email);
       $raw_email[$key] = $object->getAddress();
     }
 
     $this->setParam('raw-to', $raw_email);
     return $this;
   }
 
   public function addCCs(array $phids) {
     $phids = array_unique($phids);
     $this->setParam('cc', $phids);
     return $this;
   }
 
   public function setExcludeMailRecipientPHIDs(array $exclude) {
     $this->setParam('exclude', $exclude);
     return $this;
   }
 
   private function getExcludeMailRecipientPHIDs() {
     return $this->getParam('exclude', array());
   }
 
   public function setForceHeraldMailRecipientPHIDs(array $force) {
     $this->setParam('herald-force-recipients', $force);
     return $this;
   }
 
   private function getForceHeraldMailRecipientPHIDs() {
     return $this->getParam('herald-force-recipients', array());
   }
 
   public function getTranslation(array $objects) {
     $default_translation = PhabricatorEnv::getEnvConfig('translation.provider');
     $return = null;
     $recipients = array_merge(
       idx($this->parameters, 'to', array()),
       idx($this->parameters, 'cc', array()));
     foreach (array_select_keys($objects, $recipients) as $object) {
       $translation = null;
       if ($object instanceof PhabricatorUser) {
         $translation = $object->getTranslation();
       }
       if (!$translation) {
         $translation = $default_translation;
       }
       if ($return && $translation != $return) {
         return $default_translation;
       }
       $return = $translation;
     }
 
     if (!$return) {
       $return = $default_translation;
     }
 
     return $return;
   }
 
   public function addPHIDHeaders($name, array $phids) {
+    $phids = array_unique($phids);
     foreach ($phids as $phid) {
       $this->addHeader($name, '<'.$phid.'>');
     }
     return $this;
   }
 
   public function addHeader($name, $value) {
     $this->parameters['headers'][] = array($name, $value);
     return $this;
   }
 
   public function addAttachment(PhabricatorMetaMTAAttachment $attachment) {
     $this->parameters['attachments'][] = $attachment->toDictionary();
     return $this;
   }
 
   public function getAttachments() {
     $dicts = $this->getParam('attachments');
 
     $result = array();
     foreach ($dicts as $dict) {
       $result[] = PhabricatorMetaMTAAttachment::newFromDictionary($dict);
     }
     return $result;
   }
 
   public function setAttachments(array $attachments) {
     assert_instances_of($attachments, 'PhabricatorMetaMTAAttachment');
     $this->setParam('attachments', mpull($attachments, 'toDictionary'));
     return $this;
   }
 
   public function setFrom($from) {
     $this->setParam('from', $from);
     return $this;
   }
 
   public function setRawFrom($raw_email, $raw_name) {
     $this->setParam('raw-from', array($raw_email, $raw_name));
     return $this;
   }
 
   public function setReplyTo($reply_to) {
     $this->setParam('reply-to', $reply_to);
     return $this;
   }
 
   public function setSubject($subject) {
     $this->setParam('subject', $subject);
     return $this;
   }
 
   public function setSubjectPrefix($prefix) {
     $this->setParam('subject-prefix', $prefix);
     return $this;
   }
 
   public function setVarySubjectPrefix($prefix) {
     $this->setParam('vary-subject-prefix', $prefix);
     return $this;
   }
 
   public function setBody($body) {
     $this->setParam('body', $body);
     return $this;
   }
 
   public function setHTMLBody($html) {
     $this->setParam('html-body', $html);
     return $this;
   }
 
   public function getBody() {
     return $this->getParam('body');
   }
 
   public function getHTMLBody() {
     return $this->getParam('html-body');
   }
 
   public function setIsErrorEmail($is_error) {
     $this->setParam('is-error', $is_error);
     return $this;
   }
 
   public function getIsErrorEmail() {
     return $this->getParam('is-error', false);
   }
 
   public function getToPHIDs() {
     return $this->getParam('to', array());
   }
 
   public function getRawToAddresses() {
     return $this->getParam('raw-to', array());
   }
 
   public function getCcPHIDs() {
     return $this->getParam('cc', array());
   }
 
   /**
    * Force delivery of a message, even if recipients have preferences which
    * would otherwise drop the message.
    *
    * This is primarily intended to let users who don't want any email still
    * receive things like password resets.
    *
    * @param bool  True to force delivery despite user preferences.
    * @return this
    */
   public function setForceDelivery($force) {
     $this->setParam('force', $force);
     return $this;
   }
 
   public function getForceDelivery() {
     return $this->getParam('force', false);
   }
 
   /**
    * Flag that this is an auto-generated bulk message and should have bulk
    * headers added to it if appropriate. Broadly, this means some flavor of
    * "Precedence: bulk" or similar, but is implementation and configuration
    * dependent.
    *
    * @param bool  True if the mail is automated bulk mail.
    * @return this
    */
   public function setIsBulk($is_bulk) {
     $this->setParam('is-bulk', $is_bulk);
     return $this;
   }
 
   /**
    * Use this method to set an ID used for message threading. MetaMTA will
    * set appropriate headers (Message-ID, In-Reply-To, References and
    * Thread-Index) based on the capabilities of the underlying mailer.
    *
    * @param string  Unique identifier, appropriate for use in a Message-ID,
    *                In-Reply-To or References headers.
    * @param bool    If true, indicates this is the first message in the thread.
    * @return this
    */
   public function setThreadID($thread_id, $is_first_message = false) {
     $this->setParam('thread-id', $thread_id);
     $this->setParam('is-first-message', $is_first_message);
     return $this;
   }
 
   /**
    * Save a newly created mail to the database. The mail will eventually be
    * delivered by the MetaMTA daemon.
    *
    * @return this
    */
   public function saveAndSend() {
     return $this->save();
   }
 
   public function save() {
     if ($this->getID()) {
       return parent::save();
     }
 
     // NOTE: When mail is sent from CLI scripts that run tasks in-process, we
     // may re-enter this method from within scheduleTask(). The implementation
     // is intended to avoid anything awkward if we end up reentering this
     // method.
 
     $this->openTransaction();
       // Save to generate a task ID.
       $result = parent::save();
 
       // Queue a task to send this mail.
       $mailer_task = PhabricatorWorker::scheduleTask(
         'PhabricatorMetaMTAWorker',
         $this->getID(),
         array(
           'priority' => PhabricatorWorker::PRIORITY_ALERTS,
         ));
 
     $this->saveTransaction();
 
     return $result;
   }
 
   public function buildDefaultMailer() {
     return PhabricatorEnv::newObjectFromConfig('metamta.mail-adapter');
   }
 
 
   /**
    * Attempt to deliver an email immediately, in this process.
    *
    * @param bool  Try to deliver this email even if it has already been
    *              delivered or is in backoff after a failed delivery attempt.
    * @param PhabricatorMailImplementationAdapter Use a specific mail adapter,
    *              instead of the default.
    *
    * @return void
    */
   public function sendNow(
     $force_send = false,
     PhabricatorMailImplementationAdapter $mailer = null) {
 
     if ($mailer === null) {
       $mailer = $this->buildDefaultMailer();
     }
 
     if (!$force_send) {
       if ($this->getStatus() != self::STATUS_QUEUE) {
         throw new Exception(pht('Trying to send an already-sent mail!'));
       }
     }
 
     try {
       $params = $this->parameters;
 
       $actors = $this->loadAllActors();
       $deliverable_actors = $this->filterDeliverableActors($actors);
 
       $default_from = PhabricatorEnv::getEnvConfig('metamta.default-address');
       if (empty($params['from'])) {
         $mailer->setFrom($default_from);
       }
 
       $is_first = idx($params, 'is-first-message');
       unset($params['is-first-message']);
 
       $is_threaded = (bool)idx($params, 'thread-id');
 
       $reply_to_name = idx($params, 'reply-to-name', '');
       unset($params['reply-to-name']);
 
       $add_cc = array();
       $add_to = array();
 
       // Only try to use preferences if everything is multiplexed, so we
       // get consistent behavior.
       $use_prefs = self::shouldMultiplexAllMail();
 
       $prefs = null;
       if ($use_prefs) {
 
         // If multiplexing is enabled, some recipients will be in "Cc"
         // rather than "To". We'll move them to "To" later (or supply a
         // dummy "To") but need to look for the recipient in either the
         // "To" or "Cc" fields here.
         $target_phid = head(idx($params, 'to', array()));
         if (!$target_phid) {
           $target_phid = head(idx($params, 'cc', array()));
         }
 
         if ($target_phid) {
           $user = id(new PhabricatorUser())->loadOneWhere(
             'phid = %s',
             $target_phid);
           if ($user) {
             $prefs = $user->loadPreferences();
           }
         }
       }
 
       foreach ($params as $key => $value) {
         switch ($key) {
           case 'raw-from':
             list($from_email, $from_name) = $value;
             $mailer->setFrom($from_email, $from_name);
             break;
           case 'from':
             $from = $value;
             $actor_email = null;
             $actor_name = null;
             $actor = idx($actors, $from);
             if ($actor) {
               $actor_email = $actor->getEmailAddress();
               $actor_name = $actor->getName();
             }
             $can_send_as_user = $actor_email &&
               PhabricatorEnv::getEnvConfig('metamta.can-send-as-user');
 
             if ($can_send_as_user) {
               $mailer->setFrom($actor_email, $actor_name);
             } else {
               $from_email = coalesce($actor_email, $default_from);
               $from_name = coalesce($actor_name, pht('Phabricator'));
 
               if (empty($params['reply-to'])) {
                 $params['reply-to'] = $from_email;
                 $params['reply-to-name'] = $from_name;
               }
 
               $mailer->setFrom($default_from, $from_name);
             }
             break;
           case 'reply-to':
             $mailer->addReplyTo($value, $reply_to_name);
             break;
           case 'to':
             $to_phids = $this->expandRecipients($value);
             $to_actors = array_select_keys($deliverable_actors, $to_phids);
             $add_to = array_merge(
               $add_to,
               mpull($to_actors, 'getEmailAddress'));
             break;
           case 'raw-to':
             $add_to = array_merge($add_to, $value);
             break;
           case 'cc':
             $cc_phids = $this->expandRecipients($value);
             $cc_actors = array_select_keys($deliverable_actors, $cc_phids);
             $add_cc = array_merge(
               $add_cc,
               mpull($cc_actors, 'getEmailAddress'));
             break;
           case 'headers':
             foreach ($value as $pair) {
               list($header_key, $header_value) = $pair;
 
               // NOTE: If we have \n in a header, SES rejects the email.
               $header_value = str_replace("\n", ' ', $header_value);
 
               $mailer->addHeader($header_key, $header_value);
             }
             break;
           case 'attachments':
             $value = $this->getAttachments();
             foreach ($value as $attachment) {
               $mailer->addAttachment(
                 $attachment->getData(),
                 $attachment->getFilename(),
                 $attachment->getMimeType());
             }
             break;
           case 'subject':
             $subject = array();
 
             if ($is_threaded) {
               $add_re = PhabricatorEnv::getEnvConfig('metamta.re-prefix');
 
               if ($prefs) {
                 $add_re = $prefs->getPreference(
                   PhabricatorUserPreferences::PREFERENCE_RE_PREFIX,
                   $add_re);
               }
 
               if ($add_re) {
                 $subject[] = 'Re:';
               }
             }
 
             $subject[] = trim(idx($params, 'subject-prefix'));
 
             $vary_prefix = idx($params, 'vary-subject-prefix');
             if ($vary_prefix != '') {
               $use_subject = PhabricatorEnv::getEnvConfig(
                 'metamta.vary-subjects');
 
               if ($prefs) {
                 $use_subject = $prefs->getPreference(
                   PhabricatorUserPreferences::PREFERENCE_VARY_SUBJECT,
                   $use_subject);
               }
 
               if ($use_subject) {
                 $subject[] = $vary_prefix;
               }
             }
 
             $subject[] = $value;
 
             $mailer->setSubject(implode(' ', array_filter($subject)));
             break;
           case 'is-bulk':
             if ($value) {
               $mailer->addHeader('Precedence', 'bulk');
             }
             break;
           case 'thread-id':
 
             // NOTE: Gmail freaks out about In-Reply-To and References which
             // aren't in the form "<string@domain.tld>"; this is also required
             // by RFC 2822, although some clients are more liberal in what they
             // accept.
             $domain = PhabricatorEnv::getEnvConfig('metamta.domain');
             $value = '<'.$value.'@'.$domain.'>';
 
             if ($is_first && $mailer->supportsMessageIDHeader()) {
               $mailer->addHeader('Message-ID',  $value);
             } else {
               $in_reply_to = $value;
               $references = array($value);
               $parent_id = $this->getParentMessageID();
               if ($parent_id) {
                 $in_reply_to = $parent_id;
                 // By RFC 2822, the most immediate parent should appear last
                 // in the "References" header, so this order is intentional.
                 $references[] = $parent_id;
               }
               $references = implode(' ', $references);
               $mailer->addHeader('In-Reply-To', $in_reply_to);
               $mailer->addHeader('References',  $references);
             }
             $thread_index = $this->generateThreadIndex($value, $is_first);
             $mailer->addHeader('Thread-Index', $thread_index);
             break;
           case 'mailtags':
             // Handled below.
             break;
           case 'subject-prefix':
           case 'vary-subject-prefix':
             // Handled above.
             break;
           default:
             // Just discard.
         }
       }
 
       $body = idx($params, 'body', '');
       $max = PhabricatorEnv::getEnvConfig('metamta.email-body-limit');
       if (strlen($body) > $max) {
         $body = id(new PhutilUTF8StringTruncator())
           ->setMaximumBytes($max)
           ->truncateString($body);
         $body .= "\n";
         $body .= pht('(This email was truncated at %d bytes.)', $max);
       }
       $mailer->setBody($body);
 
       $html_emails = false;
       if ($use_prefs && $prefs) {
         $html_emails = $prefs->getPreference(
           PhabricatorUserPreferences::PREFERENCE_HTML_EMAILS,
           $html_emails);
       }
 
       if ($html_emails && isset($params['html-body'])) {
         $mailer->setHTMLBody($params['html-body']);
       }
 
       if (!$add_to && !$add_cc) {
         $this->setStatus(self::STATUS_VOID);
         $this->setMessage(
           pht(
             'Message has no valid recipients: all To/Cc are disabled, '.
             'invalid, or configured not to receive this mail.'));
         return $this->save();
       }
 
       if ($this->getIsErrorEmail()) {
         $all_recipients = array_merge($add_to, $add_cc);
         if ($this->shouldRateLimitMail($all_recipients)) {
           $this->setStatus(self::STATUS_VOID);
           $this->setMessage(
             pht(
               'This is an error email, but one or more recipients have '.
               'exceeded the error email rate limit. Declining to deliver '.
               'message.'));
           return $this->save();
         }
       }
 
       if (PhabricatorEnv::getEnvConfig('phabricator.silent')) {
         $this->setStatus(self::STATUS_VOID);
         $this->setMessage(
           pht(
             'Phabricator is running in silent mode. See `%s` '.
             'in the configuration to change this setting.',
             'phabricator.silent'));
         return $this->save();
       }
 
       $mailer->addHeader('X-Phabricator-Sent-This-Message', 'Yes');
       $mailer->addHeader('X-Mail-Transport-Agent', 'MetaMTA');
 
       // Some clients respect this to suppress OOF and other auto-responses.
       $mailer->addHeader('X-Auto-Response-Suppress', 'All');
 
       // If the message has mailtags, filter out any recipients who don't want
       // to receive this type of mail.
       $mailtags = $this->getParam('mailtags');
       if ($mailtags) {
         $tag_header = array();
         foreach ($mailtags as $mailtag) {
           $tag_header[] = '<'.$mailtag.'>';
         }
         $tag_header = implode(', ', $tag_header);
         $mailer->addHeader('X-Phabricator-Mail-Tags', $tag_header);
       }
 
       // Some mailers require a valid "To:" in order to deliver mail. If we
       // don't have any "To:", try to fill it in with a placeholder "To:".
       // If that also fails, move the "Cc:" line to "To:".
       if (!$add_to) {
         $placeholder_key = 'metamta.placeholder-to-recipient';
         $placeholder = PhabricatorEnv::getEnvConfig($placeholder_key);
         if ($placeholder !== null) {
           $add_to = array($placeholder);
         } else {
           $add_to = $add_cc;
           $add_cc = array();
         }
       }
 
       $add_to = array_unique($add_to);
       $add_cc = array_diff(array_unique($add_cc), $add_to);
 
       $mailer->addTos($add_to);
       if ($add_cc) {
         $mailer->addCCs($add_cc);
       }
     } catch (Exception $ex) {
       $this
         ->setStatus(self::STATUS_FAIL)
         ->setMessage($ex->getMessage())
         ->save();
 
       throw $ex;
     }
 
     try {
       $ok = $mailer->send();
       if (!$ok) {
         // TODO: At some point, we should clean this up and make all mailers
         // throw.
         throw new Exception(
           pht('Mail adapter encountered an unexpected, unspecified failure.'));
       }
 
       $this->setStatus(self::STATUS_SENT);
       $this->save();
 
       return $this;
     } catch (PhabricatorMetaMTAPermanentFailureException $ex) {
       $this
         ->setStatus(self::STATUS_FAIL)
         ->setMessage($ex->getMessage())
         ->save();
 
       throw $ex;
     } catch (Exception $ex) {
       $this
         ->setMessage($ex->getMessage()."\n".$ex->getTraceAsString())
         ->save();
 
       throw $ex;
     }
   }
 
   public static function getReadableStatus($status_code) {
     $readable = array(
       self::STATUS_QUEUE => pht('Queued for Delivery'),
       self::STATUS_FAIL  => pht('Delivery Failed'),
       self::STATUS_SENT  => pht('Sent'),
       self::STATUS_VOID  => pht('Void'),
     );
     $status_code = coalesce($status_code, '?');
     return idx($readable, $status_code, $status_code);
   }
 
   private function generateThreadIndex($seed, $is_first_mail) {
     // When threading, Outlook ignores the 'References' and 'In-Reply-To'
     // headers that most clients use. Instead, it uses a custom 'Thread-Index'
     // header. The format of this header is something like this (from
     // camel-exchange-folder.c in Evolution Exchange):
 
     /* A new post to a folder gets a 27-byte-long thread index. (The value
      * is apparently unique but meaningless.) Each reply to a post gets a
      * 32-byte-long thread index whose first 27 bytes are the same as the
      * parent's thread index. Each reply to any of those gets a
      * 37-byte-long thread index, etc. The Thread-Index header contains a
      * base64 representation of this value.
      */
 
     // The specific implementation uses a 27-byte header for the first email
     // a recipient receives, and a random 5-byte suffix (32 bytes total)
     // thereafter. This means that all the replies are (incorrectly) siblings,
     // but it would be very difficult to keep track of the entire tree and this
     // gets us reasonable client behavior.
 
     $base = substr(md5($seed), 0, 27);
     if (!$is_first_mail) {
       // Not totally sure, but it seems like outlook orders replies by
       // thread-index rather than timestamp, so to get these to show up in the
       // right order we use the time as the last 4 bytes.
       $base .= ' '.pack('N', time());
     }
 
     return base64_encode($base);
   }
 
   public static function shouldMultiplexAllMail() {
     return PhabricatorEnv::getEnvConfig('metamta.one-mail-per-recipient');
   }
 
 
 /* -(  Managing Recipients  )------------------------------------------------ */
 
 
   /**
    * Get all of the recipients for this mail, after preference filters are
    * applied. This list has all objects to whom delivery will be attempted.
    *
    * Note that this expands recipients into their members, because delivery
    * is never directly attempted to aggregate actors like projects.
    *
    * @return  list<phid>  A list of all recipients to whom delivery will be
    *                      attempted.
    * @task recipients
    */
   public function buildRecipientList() {
     $actors = $this->loadAllActors();
     $actors = $this->filterDeliverableActors($actors);
     return mpull($actors, 'getPHID');
   }
 
   public function loadAllActors() {
     $actor_phids = $this->getAllActorPHIDs();
     $actor_phids = $this->expandRecipients($actor_phids);
     return $this->loadActors($actor_phids);
   }
 
   private function getAllActorPHIDs() {
     return array_merge(
       array($this->getParam('from')),
       $this->getToPHIDs(),
       $this->getCcPHIDs());
   }
 
   /**
    * Expand a list of recipient PHIDs (possibly including aggregate recipients
    * like projects) into a deaggregated list of individual recipient PHIDs.
    * For example, this will expand project PHIDs into a list of the project's
    * members.
    *
    * @param list<phid>  List of recipient PHIDs, possibly including aggregate
    *                    recipients.
    * @return list<phid> Deaggregated list of mailable recipients.
    */
   private function expandRecipients(array $phids) {
     if ($this->recipientExpansionMap === null) {
       $all_phids = $this->getAllActorPHIDs();
       $this->recipientExpansionMap = id(new PhabricatorMetaMTAMemberQuery())
         ->setViewer(PhabricatorUser::getOmnipotentUser())
         ->withPHIDs($all_phids)
         ->execute();
     }
 
     $results = array();
     foreach ($phids as $phid) {
       foreach ($this->recipientExpansionMap[$phid] as $recipient_phid) {
         $results[$recipient_phid] = $recipient_phid;
       }
     }
 
     return array_keys($results);
   }
 
   private function filterDeliverableActors(array $actors) {
     assert_instances_of($actors, 'PhabricatorMetaMTAActor');
     $deliverable_actors = array();
     foreach ($actors as $phid => $actor) {
       if ($actor->isDeliverable()) {
         $deliverable_actors[$phid] = $actor;
       }
     }
     return $deliverable_actors;
   }
 
   private function loadActors(array $actor_phids) {
     $actor_phids = array_filter($actor_phids);
     $viewer = PhabricatorUser::getOmnipotentUser();
 
     $actors = id(new PhabricatorMetaMTAActorQuery())
       ->setViewer($viewer)
       ->withPHIDs($actor_phids)
       ->execute();
 
     if (!$actors) {
       return array();
     }
 
     if ($this->getForceDelivery()) {
       // If we're forcing delivery, skip all the opt-out checks. We don't
       // bother annotating reasoning on the mail in this case because it should
       // always be obvious why the mail hit this rule (e.g., it is a password
       // reset mail).
       foreach ($actors as $actor) {
         $actor->setDeliverable(PhabricatorMetaMTAActor::REASON_FORCE);
       }
       return $actors;
     }
 
     // Exclude explicit recipients.
     foreach ($this->getExcludeMailRecipientPHIDs() as $phid) {
       $actor = idx($actors, $phid);
       if (!$actor) {
         continue;
       }
       $actor->setUndeliverable(PhabricatorMetaMTAActor::REASON_RESPONSE);
     }
 
     // Before running more rules, save a list of the actors who were
     // deliverable before we started running preference-based rules. This stops
     // us from trying to send mail to disabled users just because a Herald rule
     // added them, for example.
     $deliverable = array();
     foreach ($actors as $phid => $actor) {
       if ($actor->isDeliverable()) {
         $deliverable[] = $phid;
       }
     }
 
     // For the rest of the rules, order matters. We're going to run all the
     // possible rules in order from weakest to strongest, and let the strongest
     // matching rule win. The weaker rules leave annotations behind which help
     // users understand why the mail was routed the way it was.
 
     // Exclude the actor if their preferences are set.
     $from_phid = $this->getParam('from');
     $from_actor = idx($actors, $from_phid);
     if ($from_actor) {
       $from_user = id(new PhabricatorPeopleQuery())
         ->setViewer($viewer)
         ->withPHIDs(array($from_phid))
         ->execute();
       $from_user = head($from_user);
       if ($from_user) {
         $pref_key = PhabricatorUserPreferences::PREFERENCE_NO_SELF_MAIL;
         $exclude_self = $from_user
           ->loadPreferences()
           ->getPreference($pref_key);
         if ($exclude_self) {
           $from_actor->setUndeliverable(PhabricatorMetaMTAActor::REASON_SELF);
         }
       }
     }
 
     $all_prefs = id(new PhabricatorUserPreferences())->loadAllWhere(
       'userPHID in (%Ls)',
       $actor_phids);
     $all_prefs = mpull($all_prefs, null, 'getUserPHID');
 
     $value_email = PhabricatorUserPreferences::MAILTAG_PREFERENCE_EMAIL;
 
     // Exclude all recipients who have set preferences to not receive this type
     // of email (for example, a user who says they don't want emails about task
     // CC changes).
     $tags = $this->getParam('mailtags');
     if ($tags) {
       foreach ($all_prefs as $phid => $prefs) {
         $user_mailtags = $prefs->getPreference(
           PhabricatorUserPreferences::PREFERENCE_MAILTAGS,
           array());
 
         // The user must have elected to receive mail for at least one
         // of the mailtags.
         $send = false;
         foreach ($tags as $tag) {
           if (((int)idx($user_mailtags, $tag, $value_email)) == $value_email) {
             $send = true;
             break;
           }
         }
 
         if (!$send) {
           $actors[$phid]->setUndeliverable(
             PhabricatorMetaMTAActor::REASON_MAILTAGS);
         }
       }
     }
 
     // If recipients were initially deliverable and were added by "Send me an
     // email" Herald rules, annotate them as such and make them deliverable
     // again, overriding any changes made by the  "self mail" and "mail tags"
     // settings.
     $force_recipients = $this->getForceHeraldMailRecipientPHIDs();
     $force_recipients = array_fuse($force_recipients);
     if ($force_recipients) {
       foreach ($deliverable as $phid) {
         if (isset($force_recipients[$phid])) {
           $actors[$phid]->setDeliverable(
             PhabricatorMetaMTAActor::REASON_FORCE_HERALD);
         }
       }
     }
 
     // Exclude recipients who don't want any mail. This rule is very strong
     // and runs last.
     foreach ($all_prefs as $phid => $prefs) {
       $exclude = $prefs->getPreference(
         PhabricatorUserPreferences::PREFERENCE_NO_MAIL,
         false);
       if ($exclude) {
         $actors[$phid]->setUndeliverable(
           PhabricatorMetaMTAActor::REASON_MAIL_DISABLED);
       }
     }
 
     return $actors;
   }
 
   private function shouldRateLimitMail(array $all_recipients) {
     try {
       PhabricatorSystemActionEngine::willTakeAction(
         $all_recipients,
         new PhabricatorMetaMTAErrorMailAction(),
         1);
       return false;
     } catch (PhabricatorSystemActionRateLimitException $ex) {
       return true;
     }
   }
 
 
 }
diff --git a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
index bb8348d8b7..d9eb6a791b 100644
--- a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
+++ b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
@@ -1,3058 +1,3055 @@
 <?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:
       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;
         } 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) {
 
-    // Before sending mail or publishing feed stories, reload the object
-    // subscribers to pick up changes caused by Herald (or by other side effects
-    // in various transaction phases).
-    $this->loadSubscribers($object);
-    // Hook for other edges that may need (re-)loading
+    // 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(
       $this->getActor());
     foreach ($xactions as $xaction) {
       $space_phid = $xaction->getNewValue();
 
       if ($space_phid === null) {
         if (!$all_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])) {
         $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;
   }
 
   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) {
-      $phids[] = $this->subscribers;
+      $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;
       }
 
       $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',
     );
   }
 
 }