DevTools: Avoid a race in WorkspaceDiff when UISourceCodes are removed

third_party/WebKit/Source/devtools/front_end/workspace_diff/WorkspaceDiff.js

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 
 WorkspaceDiff.WorkspaceDiff = class extends Common.Object {
   /**
    * @param {!Workspace.Workspace} workspace
    */
   constructor(workspace) {
@@ skipping 71 matching lines @@
   _uiSourceCodeAdded(event) {
     var uiSourceCode = /** @type {!Workspace.UISourceCode} */ (event.data);
     this._updateModifiedState(uiSourceCode);
   }
 
   /**
    * @param {!Common.Event} event
    */
   _uiSourceCodeRemoved(event) {
     var uiSourceCode = /** @type {!Workspace.UISourceCode} */ (event.data);
-    this._loadingUISourceCodes.delete(uiSourceCode);
-    this._markAsUnmodified(uiSourceCode);
+    this._removeUISourceCode(uiSourceCode);
   }
 
   /**
    * @param {!Common.Event} event
    */
   _projectRemoved(event) {
     var project = /** @type {!Workspace.Project} */ (event.data);
-    for (var uiSourceCode of project.uiSourceCodes()) {
-      this._loadingUISourceCodes.delete(uiSourceCode);
-      this._markAsUnmodified(uiSourceCode);
-    }
+    for (var uiSourceCode of project.uiSourceCodes())
+      this._removeUISourceCode(uiSourceCode);
+  }
+
+  _removeUISourceCode(uiSourceCode) {

[lushnikov, 2017/06/08 00:06:51]

let's jsdoc this

[einbinder, 2017/06/08 01:27:55]

Done.

+    this._loadingUISourceCodes.delete(uiSourceCode);
+    var uiSourceCodeDiff = this._uiSourceCodeDiffs.get(uiSourceCode);
+    if (uiSourceCodeDiff)
+      uiSourceCodeDiff._invalidated = true;
+    this._markAsUnmodified(uiSourceCode);
   }
 
   /**
    * @param {!Workspace.UISourceCode} uiSourceCode
    */
   _markAsUnmodified(uiSourceCode) {
     this._uiSourceCodeProcessedForTest();
     if (this._modifiedUISourceCodes.delete(uiSourceCode))
       this.dispatchEventToListeners(WorkspaceDiff.Events.ModifiedStatusChanged, {uiSourceCode, isModified: false});
   }
@@ skipping 49 matching lines @@
   /**
    * @param {!Workspace.UISourceCode} uiSourceCode
    */
   constructor(uiSourceCode) {
     super();
     this._uiSourceCode = uiSourceCode;
     uiSourceCode.addEventListener(Workspace.UISourceCode.Events.WorkingCopyChanged, this._uiSourceCodeChanged, this);
     uiSourceCode.addEventListener(Workspace.UISourceCode.Events.WorkingCopyCommitted, this._uiSourceCodeChanged, this);
     this._requestDiffPromise = null;
     this._pendingChanges = null;
+    this._invalidated = false;

[lushnikov, 2017/06/08 00:06:51]

how about this._disposed? Feels like a better name

[einbinder, 2017/06/08 01:27:55]

Done.

   }
 
   _uiSourceCodeChanged() {
     if (this._pendingChanges) {
       clearTimeout(this._pendingChanges);
       this._pendingChanges = null;
     }
     this._requestDiffPromise = null;
 
     var content = this._uiSourceCode.content();
     var delay = (!content || content.length < 65536) ? 0 : WorkspaceDiff.WorkspaceDiff.UpdateTimeout;
     this._pendingChanges = setTimeout(emitDiffChanged.bind(this), delay);
 
     /**
      * @this {WorkspaceDiff.WorkspaceDiff.UISourceCodeDiff}
      */
     function emitDiffChanged() {
+      if (this._invalidated)
+        return;
       this.dispatchEventToListeners(WorkspaceDiff.Events.DiffChanged);
       this._pendingChanges = null;
     }
   }
 
   /**
    * @return {!Promise<?Diff.Diff.DiffArray>}
    */
   requestDiff() {
     if (!this._requestDiffPromise)
       this._requestDiffPromise = this._innerRequestDiff();
     return this._requestDiffPromise;
   }
 
   /**
    * @return {!Promise<?Diff.Diff.DiffArray>}
    */
   async _innerRequestDiff() {
+    if (this._invalidated)
+      return null;
+
     var current = this._uiSourceCode.workingCopy();
     if (!current && !this._uiSourceCode.contentLoaded())
       current = await this._uiSourceCode.requestContent();

[lushnikov, 2017/06/08 00:06:51]

while we are here: let's add a huge // ------ ASYNC ----- comment like we do

[einbinder, 2017/06/08 01:27:55]

Done.

+    if (this._invalidated)
+      return null;
+
     var baseline = await this._uiSourceCode.requestOriginalContent();

[lushnikov, 2017/06/08 00:06:51]

and let's add the "ASYNC" comment here as well

[einbinder, 2017/06/08 01:27:55]

Done.

+    if (this._invalidated)
+      return null;
+
     if (current === null || baseline === null)
       return null;
     return Diff.Diff.lineDiff(baseline.split('\n'), current.split('\n'));
   }
 };
 
 /**
  * @enum {symbol}
  */
 WorkspaceDiff.Events = {
   DiffChanged: Symbol('DiffChanged'),
   ModifiedStatusChanged: Symbol('ModifiedStatusChanged')
 };
 
 /**
  * @return {!WorkspaceDiff.WorkspaceDiff}
  */
 WorkspaceDiff.workspaceDiff = function() {
   if (!WorkspaceDiff.WorkspaceDiff._instance)
     WorkspaceDiff.WorkspaceDiff._instance = new WorkspaceDiff.WorkspaceDiff(Workspace.workspace);
   return WorkspaceDiff.WorkspaceDiff._instance;
 };
 
 WorkspaceDiff.WorkspaceDiff.UpdateTimeout = 200;