Allow dashboard panels to detect rendering cycles and arrest stack overflows

Summary:
Ref T4986. Ref T4983. Panels will soon be able to contain other panels, either via Remarkup (`{W1}`) or maybe through new types of meta-panels.

Allow panels to detect that they are being rendered very deeply and/or within themselves.

Test Plan: Faked some errors, got failed panel renders. Since panels can't //really// contain other panels yet, this doesn't really have an impact.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: chad, epriestley

Maniphest Tasks: T4983, T4986

Differential Revision: https://secure.phabricator.com/D9140

resources/celerity/map.php

@@ -52,7 +52,7 @@ return array(
     'rsrc/css/application/conpherence/widget-pane.css' => 'bf275a6c',
     'rsrc/css/application/contentsource/content-source-view.css' => '4b8b05d4',
     'rsrc/css/application/countdown/timer.css' => '86b7b0a0',
-    'rsrc/css/application/dashboard/dashboard.css' => '5b532b7b',
+    'rsrc/css/application/dashboard/dashboard.css' => '2b41640b',
     'rsrc/css/application/diff/inline-comment-summary.css' => '8cfd34e8',
     'rsrc/css/application/differential/add-comment.css' => 'c478bcaa',
     'rsrc/css/application/differential/changeset-view.css' => '1570a1ff',
@@ -358,8 +358,8 @@ return array(
     'rsrc/js/application/conpherence/behavior-pontificate.js' => '53f6f2dd',
     'rsrc/js/application/conpherence/behavior-widget-pane.js' => '40b1ff90',
     'rsrc/js/application/countdown/timer.js' => '889c96f3',
-    'rsrc/js/application/dashboard/behavior-dashboard-async-panel.js' => '4398eabb',
-    'rsrc/js/application/dashboard/behavior-dashboard-move-panels.js' => 'aa3f313b',
+    'rsrc/js/application/dashboard/behavior-dashboard-async-panel.js' => 'fd965b41',
+    'rsrc/js/application/dashboard/behavior-dashboard-move-panels.js' => 'fa187a68',
     'rsrc/js/application/differential/DifferentialInlineCommentEditor.js' => 'f2441746',
     'rsrc/js/application/differential/behavior-add-reviewers-and-ccs.js' => '533a187b',
     'rsrc/js/application/differential/behavior-comment-jump.js' => '71755c79',
@@ -553,8 +553,8 @@ return array(
     'javelin-behavior-conpherence-widget-pane' => '40b1ff90',
     'javelin-behavior-countdown-timer' => '889c96f3',
     'javelin-behavior-dark-console' => 'e9fdb5e5',
-    'javelin-behavior-dashboard-async-panel' => '4398eabb',
-    'javelin-behavior-dashboard-move-panels' => 'aa3f313b',
+    'javelin-behavior-dashboard-async-panel' => 'fd965b41',
+    'javelin-behavior-dashboard-move-panels' => 'fa187a68',
     'javelin-behavior-device' => '03d6ed07',
     'javelin-behavior-differential-add-reviewers-and-ccs' => '533a187b',
     'javelin-behavior-differential-comment-jump' => '71755c79',
@@ -701,7 +701,7 @@ return array(
     'phabricator-core-css' => '40151074',
     'phabricator-countdown-css' => '86b7b0a0',
     'phabricator-crumbs-view-css' => '6a23399c',
-    'phabricator-dashboard-css' => '5b532b7b',
+    'phabricator-dashboard-css' => '2b41640b',
     'phabricator-drag-and-drop-file-upload' => 'ae6abfba',
     'phabricator-draggable-list' => '1681c4d4',
     'phabricator-fatal-config-template-css' => '25d446d6',
@@ -1133,12 +1133,6 @@ return array(
       8 => 'phuix-action-list-view',
       9 => 'phuix-action-view',
     ),
-    '4398eabb' =>
-    array(
-      0 => 'javelin-behavior',
-      1 => 'javelin-dom',
-      2 => 'javelin-workflow',
-    ),
     '441f2137' =>
     array(
       0 => 'javelin-behavior',
@@ -1270,11 +1264,6 @@ return array(
       2 => 'javelin-util',
       3 => 'phabricator-shaped-request',
     ),
-    '7319e029' =>
-    array(
-      0 => 'javelin-behavior',
-      1 => 'javelin-dom',
-    ),
     '62e18640' =>
     array(
       0 => 'javelin-install',
@@ -1329,6 +1318,11 @@ return array(
       1 => 'javelin-stratcom',
       2 => 'javelin-dom',
     ),
+    '7319e029' =>
+    array(
+      0 => 'javelin-behavior',
+      1 => 'javelin-dom',
+    ),
     '76f4ebed' =>
     array(
       0 => 'javelin-install',
@@ -1598,15 +1592,6 @@ return array(
       1 => 'javelin-stratcom',
       2 => 'javelin-dom',
     ),
-    'aa3f313b' =>
-    array(
-      0 => 'javelin-behavior',
-      1 => 'javelin-dom',
-      2 => 'javelin-util',
-      3 => 'javelin-stratcom',
-      4 => 'javelin-workflow',
-      5 => 'phabricator-draggable-list',
-    ),
     'ad7a69ca' =>
     array(
       0 => 'javelin-install',
@@ -2034,11 +2019,26 @@ return array(
       4 => 'javelin-stratcom',
       5 => 'phabricator-shaped-request',
     ),
+    'fa187a68' =>
+    array(
+      0 => 'javelin-behavior',
+      1 => 'javelin-dom',
+      2 => 'javelin-util',
+      3 => 'javelin-stratcom',
+      4 => 'javelin-workflow',
+      5 => 'phabricator-draggable-list',
+    ),
     'fbbce3bf' =>
     array(
       0 => 'phabricator-busy',
       1 => 'javelin-behavior',
     ),
+    'fd965b41' =>
+    array(
+      0 => 'javelin-behavior',
+      1 => 'javelin-dom',
+      2 => 'javelin-workflow',
+    ),
     'fe2e0ba4' =>
     array(
       0 => 'javelin-behavior',

src/applications/dashboard/controller/PhabricatorDashboardPanelRenderController.php

@@ -21,9 +21,22 @@ final class PhabricatorDashboardPanelRenderController
       return new Aphront404Response();
     }
 
+    if ($request->isAjax()) {
+      $parent_phids = $request->getStrList('parentPanelPHIDs', null);
+      if ($parent_phids === null) {
+        throw new Exception(
+          pht(
+            'Required parameter `parentPanelPHIDs` is not present in '.
+            'request.'));
+      }
+    } else {
+      $parent_phids = array();
+    }
+
     $rendered_panel = id(new PhabricatorDashboardPanelRenderingEngine())
       ->setViewer($viewer)
       ->setPanel($panel)
+      ->setParentPanelPHIDs($parent_phids)
       ->renderPanel();
 
     if ($request->isAjax()) {

src/applications/dashboard/controller/PhabricatorDashboardPanelViewController.php

@@ -41,6 +41,7 @@ final class PhabricatorDashboardPanelViewController
     $rendered_panel = id(new PhabricatorDashboardPanelRenderingEngine())
       ->setViewer($viewer)
       ->setPanel($panel)
+      ->setParentPanelPHIDs(array())
       ->renderPanel();
 
     return $this->buildApplicationPage(

src/applications/dashboard/engine/PhabricatorDashboardPanelRenderingEngine.php

@@ -5,6 +5,7 @@ final class PhabricatorDashboardPanelRenderingEngine extends Phobject {
   private $panel;
   private $viewer;
   private $enableAsyncRendering;
+  private $parentPanelPHIDs;
 
   /**
    * Allow the engine to render the panel via Ajax.
@@ -14,6 +15,11 @@ final class PhabricatorDashboardPanelRenderingEngine extends Phobject {
     return $this;
   }
 
+  public function setParentPanelPHIDs(array $parents) {
+    $this->parentPanelPHIDs = $parents;
+    return $this;
+  }
+
   public function setViewer(PhabricatorUser $viewer) {
     $this->viewer = $viewer;
     return $this;
@@ -44,13 +50,15 @@ final class PhabricatorDashboardPanelRenderingEngine extends Phobject {
           $panel->getPanelType()));
     }
 
+    try {
+      $this->detectRenderingCycle($panel);
+
       if ($this->enableAsyncRendering) {
         if ($panel_type->shouldRenderAsync()) {
           return $this->renderAsyncPanel($panel);
         }
       }
 
-    try {
       return $panel_type->renderPanel($viewer, $panel);
     } catch (Exception $ex) {
       return $this->renderErrorPanel(
@@ -75,6 +83,7 @@ final class PhabricatorDashboardPanelRenderingEngine extends Phobject {
       'dashboard-async-panel',
       array(
         'panelID' => $panel_id,
+        'parentPanelPHIDs' => $this->parentPanelPHIDs,
         'uri' => '/dashboard/panel/render/'.$panel->getID().'/',
       ));
 
@@ -87,4 +96,43 @@ final class PhabricatorDashboardPanelRenderingEngine extends Phobject {
       ->appendChild(pht('Loading...'));
   }
 
+  /**
+   * Detect graph cycles in panels, and deeply nested panels.
+   *
+   * This method throws if the current rendering stack is too deep or contains
+   * a cycle. This can happen if you embed layout panels inside each other,
+   * build a big stack of panels, or embed a panel in remarkup inside another
+   * panel. Generally, all of this stuff is ridiculous and we just want to
+   * shut it down.
+   *
+   * @param PhabricatorDashboardPanel Panel being rendered.
+   * @return void
+   */
+  private function detectRenderingCycle(PhabricatorDashboardPanel $panel) {
+    if ($this->parentPanelPHIDs === null) {
+      throw new Exception(
+        pht(
+          'You must call setParentPanelPHIDs() before rendering panels.'));
+    }
+
+    $max_depth = 4;
+    if (count($this->parentPanelPHIDs) >= $max_depth) {
+      throw new Exception(
+        pht(
+          'To render more than %s levels of panels nested inside other '.
+          'panels, purchase a subscription to Phabricator Gold.',
+          new PhutilNumber($max_depth)));
+    }
+
+    if (in_array($panel->getPHID(), $this->parentPanelPHIDs)) {
+      throw new Exception(
+        pht(
+          'You awake in a twisting maze of mirrors, all alike. '.
+          'You are likely to be eaten by a graph cycle. '.
+          'Should you escape alive, you resolve to be more careful about '.
+          'putting dashboard panels inside themselves.'));
+    }
+  }
+
+
 }

src/applications/dashboard/engine/PhabricatorDashboardRenderingEngine.php

@@ -43,6 +43,7 @@ final class PhabricatorDashboardRenderingEngine extends Phobject {
           ->setViewer($viewer)
           ->setPanel($panel)
           ->setEnableAsyncRendering(true)
+          ->setParentPanelPHIDs(array())
           ->renderPanel();
       }
       $column_class = $layout_config->getColumnClass(

webroot/rsrc/js/application/dashboard/behavior-dashboard-async-panel.js

@@ -10,6 +10,7 @@ JX.behavior('dashboard-async-panel', function(config) {
   panel.style.opacity = '0.5';
 
   new JX.Workflow(config.uri)
+    .setData({parentPanelPHIDs: config.parentPanelPHIDs.join(',')})
     .setHandler(function(r) {
       JX.DOM.replace(panel, JX.$H(r.panelMarkup));
     })