DevTools: Diff subsystem

third_party/WebKit/Source/devtools/front_end/workspace_diff/UISourceCodeDiff.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.
+
+/**
+ * @param {!Workspace.UISourceCode} uiSourceCode
+ * @return {!Promise<!Diff.Diff.DiffArray>}
+ */
+WorkspaceDiff.requestDiff = function(uiSourceCode) {
+  return WorkspaceDiff._uiSourceCodeDiff(uiSourceCode).requestDiff();
+};
+
+/**
+ * @param {!Workspace.UISourceCode} uiSourceCode
+ * @param {function(!WorkspaceDiff.DiffChangedEvent)} callback
+ * @param {!Object=} thisObj
+ */
+WorkspaceDiff.addThrottledDiffListener = function(uiSourceCode, callback, thisObj) {

[lushnikov, 2017/03/08 17:55:16]

.subscribeToDiffChange(..)

[einbinder, 2017/03/08 23:12:47]

Done.

+  WorkspaceDiff._uiSourceCodeDiff(uiSourceCode).on(WorkspaceDiff.DiffChangedEvent, callback, thisObj);
+};
+
+/**
+ * @param {!Workspace.UISourceCode} uiSourceCode
+ * @param {function(!WorkspaceDiff.DiffChangedEvent)} callback
+ * @param {!Object=} thisObj
+ */
+WorkspaceDiff.removeThrottledDiffListener = function(uiSourceCode, callback, thisObj) {
+  WorkspaceDiff._uiSourceCodeDiff(uiSourceCode).off(WorkspaceDiff.DiffChangedEvent, callback, thisObj);
+};
+
+/**
+ * @param {!Workspace.UISourceCode} uiSourceCode
+ * @return {!WorkspaceDiff._UISourceCodeDiff}
+ */
+WorkspaceDiff._uiSourceCodeDiff = function(uiSourceCode) {
+  if (!uiSourceCode[WorkspaceDiff._uiSourceCodeDiff.Symbol])
+    uiSourceCode[WorkspaceDiff._UISourceCodeDiff.Symbol] = new WorkspaceDiff._UISourceCodeDiff(uiSourceCode);
+  return uiSourceCode[WorkspaceDiff._UISourceCodeDiff.Symbol];
+};
+
+WorkspaceDiff._UISourceCodeDiff = class extends Common.Object {

[lushnikov, 2017/03/08 17:55:16]

Let's do the following: 
1. introduce class WorkspaceDiff
2. make it a singleton which is created in Main.js, see workspace for example
3. embed all the static methods inside the class, defining it's api

[einbinder, 2017/03/08 23:12:47]

This will pull the Diff module into autostart.

+  /**
+   * @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;
+  }
+
+  _uiSourceCodeChanged() {
+    if (this._pendingChanges) {
+      clearTimeout(this._pendingChanges);
+      this._pendingChanges = null;
+    }
+    this._requestDiffPromise = null;
+    if (!this.hasEventListeners(WorkspaceDiff.DiffChangedEvent))

[lushnikov, 2017/03/08 17:55:16]

we can omit this check - there's already one in the Common.Object.emit code

[einbinder, 2017/03/08 23:12:47]

Removed.

+      return;
+
+    var content = this._uiSourceCode.content();
+    if (content && content.length < 65536)

[lushnikov, 2017/03/08 17:55:16]

typeof content === 'string' 

+      emitDiffChanged.call(this);

[lushnikov, 2017/03/08 17:55:16]

let's always call the throttled event through timeout to be always asynchronous

[einbinder, 2017/03/08 23:12:47]

Done.

+    else
+      this._pendingChanges = setTimeout(emitDiffChanged.bind(this), 200);
+
+    /**
+     * @this {WorkspaceDiff._UISourceCodeDiff}
+     */
+    function emitDiffChanged() {
+      this.emit(new WorkspaceDiff.DiffChangedEvent());
+      this._pendingChanges = null;
+    }
+  }
+
+  /**
+   * @return {!Promise<!Diff.Diff.DiffArray>}
+   */
+  requestDiff() {
+    if (!this._requestDiffPromise) {
+      this._requestDiffPromise = this._uiSourceCode.requestOriginalContent().then(baseline => {
+        var current = this._uiSourceCode.workingCopy();
+        var diff = Diff.Diff.lineDiff(baseline.split('\n'), current.split('\n'));
+        return diff || [];
+      });
+    }
+    return this._requestDiffPromise;
+  }
+};
+
+/**
+ * @implements {Common.Emittable}
+ */
+WorkspaceDiff.DiffChangedEvent = class {};
+
+WorkspaceDiff._UISourceCodeDiff.Symbol = Symbol('WorkspaceDiff._UISourceCodeDiff.Symbol');