Build an event dispatch mechanism into Phabricator

Summary:
This is an attempt to satisfy a lot of the one-off requests a little more
generally, by providing a relatively generic piece of event architecture.

Allow the registation of event listeners which can react to various application
events (currently, task editing).

I'll doc this a bit better but I wanted to see if anyone had massive objections
to doing this or the broad approach. The specific problem I want to address is
that one client wants to do a bunch of routing for tasks via email, so it's
either build a hook, or have them override most of ManiphestReplyHandler, or
something slightly more general like this.

Test Plan: Wrote a silly listener that adds "Quack!" to a task every time it is
edited and edited some tasks. I was justly rewarded.

Reviewers: nh, jungejason, tuomaspelkonen, aran

Reviewed By: aran

CC: aran, epriestley

Differential Revision: 881

Author: epriestley

conf/default.conf.php

@@ -602,7 +602,6 @@
   // projects that want to expose an activity feed on the project homepage.
   'feed.public' => false,
 
-
 // -- Customization --------------------------------------------------------- //
 
   // Paths to additional phutil libraries to load.
@@ -636,7 +635,13 @@
   // settings are the defaults.)
   'celerity.force-disk-reads' => false,
 
-  // -- Pygments ------------------------------------------------------------ //
+  // You can respond to various application events by installing listeners,
+  // which will receive callbacks when interesting things occur. Specify a list
+  // of classes which extend PhabricatorEventListener here.
+  'events.listeners'  => array(),
+
+// -- Pygments -------------------------------------------------------------- //
+
   // Phabricator can highlight PHP by default, but if you want syntax
   // highlighting for other languages you should install the python package
   // 'Pygments', make sure the 'pygmentize' script is available in the

scripts/__init_script__.php

@@ -33,3 +33,4 @@
 // NOTE: This is dangerous in general, but we know we're in a script context and
 // are not vulnerable to CSRF.
 AphrontWriteGuard::allowDangerousUnguardedWrites(true);
+PhabricatorEventEngine::initialize();

src/__phutil_library_map__.php

@@ -412,6 +412,11 @@
     'PhabricatorEmailLoginController' => 'applications/auth/controller/email',
     'PhabricatorEmailTokenController' => 'applications/auth/controller/emailtoken',
     'PhabricatorEnv' => 'infrastructure/env',
+    'PhabricatorEvent' => 'infrastructure/events/event',
+    'PhabricatorEventConstants' => 'infrastructure/events/constant/base',
+    'PhabricatorEventEngine' => 'infrastructure/events/engine',
+    'PhabricatorEventListener' => 'infrastructure/events/listener',
+    'PhabricatorEventType' => 'infrastructure/events/constant/type',
     'PhabricatorFeedConstants' => 'applications/feed/constants/base',
     'PhabricatorFeedController' => 'applications/feed/controller/base',
     'PhabricatorFeedDAO' => 'applications/feed/storage/base',
@@ -1050,6 +1055,7 @@
     'PhabricatorDraftDAO' => 'PhabricatorLiskDAO',
     'PhabricatorEmailLoginController' => 'PhabricatorAuthController',
     'PhabricatorEmailTokenController' => 'PhabricatorAuthController',
+    'PhabricatorEventType' => 'PhabricatorEventConstants',
     'PhabricatorFeedController' => 'PhabricatorController',
     'PhabricatorFeedDAO' => 'PhabricatorLiskDAO',
     'PhabricatorFeedPublicStreamController' => 'PhabricatorFeedController',

src/applications/conduit/method/maniphest/createtask/ConduitAPI_maniphest_createtask_Method.php

@@ -103,6 +103,20 @@ protected function execute(ConduitAPIRequest $request) {
       $transactions[] = $transaction;
     }
 
+    $event = new PhabricatorEvent(
+      PhabricatorEventType::TYPE_MANIPHEST_WILLEDITTASK,
+      array(
+        'task'          => $task,
+        'new'           => true,
+        'transactions'  => $transactions,
+      ));
+    $event->setUser($request->getUser());
+    $event->setConduitRequest($request);
+    PhabricatorEventEngine::dispatchEvent($event);
+
+    $task = $event->getValue('task');
+    $transactions = $event->getValue('transactions');
+
     $editor = new ManiphestTransactionEditor();
     $editor->applyTransactions($task, $transactions);
 

src/applications/conduit/method/maniphest/createtask/__init__.php

@@ -15,6 +15,9 @@
 phutil_require_module('phabricator', 'applications/maniphest/storage/transaction');
 phutil_require_module('phabricator', 'applications/metamta/contentsource/source');
 phutil_require_module('phabricator', 'applications/phid/constants');
+phutil_require_module('phabricator', 'infrastructure/events/constant/type');
+phutil_require_module('phabricator', 'infrastructure/events/engine');
+phutil_require_module('phabricator', 'infrastructure/events/event');
 
 
 phutil_require_source('ConduitAPI_maniphest_createtask_Method.php');

src/applications/maniphest/controller/taskedit/ManiphestTaskEditController.php

@@ -201,6 +201,21 @@ public function processRequest() {
         }
 
         if ($transactions) {
+
+          $event = new PhabricatorEvent(
+            PhabricatorEventType::TYPE_MANIPHEST_WILLEDITTASK,
+            array(
+              'task'          => $task,
+              'new'           => !$task->getID(),
+              'transactions'  => $transactions,
+            ));
+          $event->setUser($user);
+          $event->setAphrontRequest($request);
+          PhabricatorEventEngine::dispatchEvent($event);
+
+          $task = $event->getValue('task');
+          $transactions = $event->getValue('transactions');
+
           $editor = new ManiphestTransactionEditor();
           $editor->applyTransactions($task, $transactions);
         }

src/applications/maniphest/controller/taskedit/__init__.php

@@ -22,6 +22,9 @@
 phutil_require_module('phabricator', 'applications/phid/handle/data');
 phutil_require_module('phabricator', 'infrastructure/celerity/api');
 phutil_require_module('phabricator', 'infrastructure/env');
+phutil_require_module('phabricator', 'infrastructure/events/constant/type');
+phutil_require_module('phabricator', 'infrastructure/events/engine');
+phutil_require_module('phabricator', 'infrastructure/events/event');
 phutil_require_module('phabricator', 'infrastructure/javelin/api');
 phutil_require_module('phabricator', 'infrastructure/javelin/markup');
 phutil_require_module('phabricator', 'view/form/base');

src/applications/maniphest/controller/transactionsave/ManiphestTransactionSaveController.php

@@ -229,6 +229,20 @@ public function processRequest() {
       $transaction->setContentSource($content_source);
     }
 
+    $event = new PhabricatorEvent(
+      PhabricatorEventType::TYPE_MANIPHEST_WILLEDITTASK,
+      array(
+        'task'          => $task,
+        'new'           => false,
+        'transactions'  => $transactions,
+      ));
+    $event->setUser($user);
+    $event->setAphrontRequest($request);
+    PhabricatorEventEngine::dispatchEvent($event);
+
+    $task = $event->getValue('task');
+    $transactions = $event->getValue('transactions');
+
     $editor = new ManiphestTransactionEditor();
     $editor->applyTransactions($task, $transactions);
 

src/applications/maniphest/controller/transactionsave/__init__.php

@@ -19,6 +19,9 @@
 phutil_require_module('phabricator', 'applications/markup/engine');
 phutil_require_module('phabricator', 'applications/metamta/contentsource/source');
 phutil_require_module('phabricator', 'applications/phid/constants');
+phutil_require_module('phabricator', 'infrastructure/events/constant/type');
+phutil_require_module('phabricator', 'infrastructure/events/engine');
+phutil_require_module('phabricator', 'infrastructure/events/event');
 
 phutil_require_module('phutil', 'utils');
 

src/applications/maniphest/replyhandler/ManiphestReplyHandler.php

@@ -150,6 +150,21 @@ public function receiveEmail(PhabricatorMetaMTAReceivedMail $mail) {
       $xactions[] = $file_xaction;
     }
 
+    $event = new PhabricatorEvent(
+      PhabricatorEventType::TYPE_MANIPHEST_WILLEDITTASK,
+      array(
+        'task'          => $task,
+        'mail'          => $mail,
+        'new'           => $is_new_task,
+        'transactions'  => $xactions,
+      ));
+    $event->setUser($user);
+    PhabricatorEventEngine::dispatchEvent($event);
+
+    $task = $event->getValue('task');
+    $xactions = $event->getValue('transactions');
+
+
     $editor = new ManiphestTransactionEditor();
     $editor->setParentMessageID($mail->getMessageID());
     $editor->applyTransactions($task, $xactions);

src/applications/maniphest/replyhandler/__init__.php

@@ -14,6 +14,9 @@
 phutil_require_module('phabricator', 'applications/metamta/replyhandler/base');
 phutil_require_module('phabricator', 'applications/phid/constants');
 phutil_require_module('phabricator', 'infrastructure/env');
+phutil_require_module('phabricator', 'infrastructure/events/constant/type');
+phutil_require_module('phabricator', 'infrastructure/events/engine');
+phutil_require_module('phabricator', 'infrastructure/events/event');
 
 phutil_require_module('phutil', 'utils');
 

src/docs/userguide/events.diviner

@@ -0,0 +1,27 @@
+@title Events User Guide: Installing Event Listeners
+@group userguide
+
+Using Phabricator event listeners to customize behavior.
+
+= Overview =
+
+Phabricator allows you to install custom runtime event listeners which can react
+to certain things happening (like a Maniphest Task being edited) and run custom
+code to perform logging, synchronize with other systems, or modify workflows.
+
+NOTE: This feature is new and experimental, so few events are available and
+things might not be completely stable.
+
+= Available Events =
+
+== PhabricatorEventType::TYPE_MANIPHEST_WILLEDITTASK ==
+
+This event is dispatched before a task is edited, and allows you to respond to
+or alter the edit. Data available on this event:
+
+  - ##task## The {@class:ManiphestTask} being edited.
+  - ##transactions## The list of edits (objects of class
+    @{class:ManiphestTransaction}) being applied.
+  - ##new## A boolean indicating if this task is being created.
+  - ##mail## If this edit originates from email, the
+    @{class:PhabricatorMetaMTAReceivedMail} object.

src/infrastructure/events/constant/base/PhabricatorEventConstants.php

@@ -0,0 +1,21 @@
+<?php
+
+/*
+ * Copyright 2011 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+abstract class PhabricatorEventConstants {
+
+}

src/infrastructure/events/constant/base/__init__.php

@@ -0,0 +1,10 @@
+<?php
+/**
+ * This file is automatically generated. Lint this module to rebuild it.
+ * @generated
+ */
+
+
+
+
+phutil_require_source('PhabricatorEventConstants.php');

src/infrastructure/events/constant/type/PhabricatorEventType.php

@@ -0,0 +1,23 @@
+<?php
+
+/*
+ * Copyright 2011 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+final class PhabricatorEventType extends PhabricatorEventConstants {
+
+  const TYPE_MANIPHEST_WILLEDITTASK = 'maniphest.willEditTask';
+
+}

src/infrastructure/events/constant/type/__init__.php

@@ -0,0 +1,12 @@
+<?php
+/**
+ * This file is automatically generated. Lint this module to rebuild it.
+ * @generated
+ */
+
+
+
+phutil_require_module('phabricator', 'infrastructure/events/constant/base');
+
+
+phutil_require_source('PhabricatorEventType.php');

src/infrastructure/events/engine/PhabricatorEventEngine.php

@@ -0,0 +1,68 @@
+<?php
+
+/*
+ * Copyright 2011 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+class PhabricatorEventEngine {
+
+  private static $instance;
+
+  private $listeners = array();
+
+  private function __construct() {
+    // <empty>
+  }
+
+  public static function initialize() {
+    self::$instance = new PhabricatorEventEngine();
+
+    // Instantiate and register custom event listeners so they can react to
+    // events.
+    $listeners = PhabricatorEnv::getEnvConfig('events.listeners');
+    foreach ($listeners as $listener) {
+      id(new $listener())->register();
+    }
+  }
+
+  public static function getInstance() {
+    if (!self::$instance) {
+      throw new Exception("Event engine has not been initialized!");
+    }
+    return self::$instance;
+  }
+
+  public function addListener(
+    PhabricatorEventListener $listener,
+    $type) {
+    $this->listeners[$type][] = $listener;
+    return $this;
+  }
+
+  public static function dispatchEvent(PhabricatorEvent $event) {
+    $instance = self::getInstance();
+
+    $listeners = idx($instance->listeners, $event->getType(), array());
+    foreach ($listeners as $listener) {
+      if ($event->isStopped()) {
+        // Do this first so if someone tries to dispatch a stopped event it
+        // doesn't go anywhere. Silly but less surprising.
+        break;
+      }
+      $listener->handleEvent($event);
+    }
+  }
+
+}

src/infrastructure/events/engine/__init__.php

@@ -0,0 +1,14 @@
+<?php
+/**
+ * This file is automatically generated. Lint this module to rebuild it.
+ * @generated
+ */
+
+
+
+phutil_require_module('phabricator', 'infrastructure/env');
+
+phutil_require_module('phutil', 'utils');
+
+
+phutil_require_source('PhabricatorEventEngine.php');