DevTools: Diff subsystem

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

Index: third_party/WebKit/Source/devtools/front_end/workspace_diff/UISourceCodeDiff.js
diff --git a/third_party/WebKit/Source/devtools/front_end/workspace_diff/UISourceCodeDiff.js b/third_party/WebKit/Source/devtools/front_end/workspace_diff/UISourceCodeDiff.js
new file mode 100644
index 0000000000000000000000000000000000000000..7ca0ae2d916926bae5153c40cb62832b8a266cdc
--- /dev/null
+++ b/third_party/WebKit/Source/devtools/front_end/workspace_diff/UISourceCodeDiff.js
@@ -0,0 +1,74 @@
+// 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.UISourceCodeDiff = class extends Common.Object {
+  /**
+   * @param {!Workspace.UISourceCode} uiSourceCode
+   */
+  constructor(uiSourceCode) {
+    super();
+    this.uiSourceCode = uiSourceCode;

[lushnikov, 2017/03/04 04:00:28]

private?

[einbinder, 2017/03/07 06:03:31]

Ok

+    uiSourceCode.addEventListener(
+        Workspace.UISourceCode.Events.WorkingCopyChanged, this._uiSourceCodeChanged.bind(this));

[lushnikov, 2017/03/04 04:00:28]

don't bind, pass "this" as a third parameter

[einbinder, 2017/03/07 06:03:31]

Ok

+    uiSourceCode.addEventListener(
+        Workspace.UISourceCode.Events.WorkingCopyCommitted, this._uiSourceCodeChanged.bind(this));

[lushnikov, 2017/03/04 04:00:28]

ditt

[einbinder, 2017/03/07 06:03:31]

Done.

+    this._requestDiffPromise = null;
+    this._pendingChanges = null;
+  }
+
+  /**
+   * @param {!Workspace.UISourceCode} uiSourceCode
+   * @return {!WorkspaceDiff.UISourceCodeDiff}
+   */
+  static forUISourceCode(uiSourceCode) {
+    if (!uiSourceCode[WorkspaceDiff.UISourceCodeDiff.Symbol])

[lushnikov, 2017/03/04 04:00:28]

symbol should be private 

[einbinder, 2017/03/07 06:03:31]

Done.

+      uiSourceCode[WorkspaceDiff.UISourceCodeDiff.Symbol] = new WorkspaceDiff.UISourceCodeDiff(uiSourceCode);
+    return uiSourceCode[WorkspaceDiff.UISourceCodeDiff.Symbol];
+  }
+
+  _uiSourceCodeChanged() {
+    if (this._pendingChanges) {
+      clearTimeout(this._pendingChanges);
+      this._pendingChanges = null;
+    }
+    this._requestDiffPromise = null;

[lushnikov, 2017/03/04 04:00:28]

can we fire event here, and defer all the actual work until the diff is
requested?

[einbinder, 2017/03/07 06:03:31]

Done.

+    if (!this.hasEventListeners(WorkspaceDiff.UISourceCodeDiff.DiffChangedEvent))
+      return;
+
+    var content = this.uiSourceCode.content();
+    if (content && content.length < 65536)
+      emitDiffChanged.call(this);
+    else
+      this._pendingChanges = setTimeout(emitDiffChanged.bind(this), 200);

[lushnikov, 2017/03/04 04:00:28]

you should throttle on the view side, not at the model side.

[einbinder, 2017/03/07 06:03:31]

If it doesn't get throttled here, then there is no guarantee that different
views will request the same diffs.

+
+    /**
+     * @this {WorkspaceDiff.UISourceCodeDiff}
+     */
+    function emitDiffChanged() {
+      this.emit(new WorkspaceDiff.UISourceCodeDiff.DiffChangedEvent());
+      this._pendingChanges = null;
+    }
+  }
+
+  /**
+   * @return {!Promise<!Diff.Diff.DiffArray>}
+   */
+  requestDiff() {

[lushnikov, 2017/03/04 04:00:28]

can we make this accept uiSourceCode as an argument and return a throw-away
object as result? the design would feel more light-weight.

Benefits:
- you would be able to name this like WorkspaceDiff
- you would have a place to put the changedSourceCodes() and other methods

Downsides:
- you'll have to implement "[un]subscribeForDiffChange(uiSourceCode)" method

[einbinder, 2017/03/07 06:03:31]

Made these top level functions.

+    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.UISourceCodeDiff.DiffChangedEvent = class {};
+
+WorkspaceDiff.UISourceCodeDiff.Symbol = Symbol('WorkspaceDiff.UISourceCodeDiff.Symbol');