[AI Assistance] Ignore changes that don't have a diff

Updates the lineDiff to return empty array of changes
when both the original and the changed text are
equal.
Then check in the CombinedDiffView whether there were
actual diff before rendering.

Bug: 406699819
Change-Id: I3f637f22b42a0eb4853b9897c2ea08fc632f79ea
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6404313
Reviewed-by: Ergün Erdoğmuş <[email protected]>
Commit-Queue: Nikolay Vitkov <[email protected]>

Author: Lightning00Blade

front_end/panels/changes/CombinedDiffView.test.ts

@@ -46,16 +46,16 @@ function createWorkspaceDiff({workspace}: {workspace: Workspace.Workspace.Worksp
 
 async function createCombinedDiffView({workspaceDiff}: {workspaceDiff: WorkspaceDiff.WorkspaceDiff.WorkspaceDiffImpl}) {
   const view = createViewFunctionStub(CombinedDiffView.CombinedDiffView);
-  const combinedDiffView = new CombinedDiffView.CombinedDiffView(undefined, view);
-  combinedDiffView.workspaceDiff = workspaceDiff;
+  const widget = new CombinedDiffView.CombinedDiffView(undefined, view);
+  widget.workspaceDiff = workspaceDiff;
 
   const container = document.createElement('div');
   renderElementIntoDOM(container);
-  combinedDiffView.markAsRoot();
-  combinedDiffView.show(container);
+  widget.markAsRoot();
+  widget.show(container);
   await view.nextInput;
 
-  return {combinedDiffView, view};
+  return {widget, view};
 }
 
 describeWithEnvironment('CombinedDiffView', () => {

front_end/panels/changes/CombinedDiffView.ts

@@ -178,18 +178,22 @@ export class CombinedDiffView extends UI.Widget.Widget {
   }
 
   override async performUpdate(): Promise<void> {
-    const uiSourceCodeAndDiffs = await Promise.all(this.#modifiedUISourceCodes.map(async modifiedUISourceCode => {
-      // `requestDiff` caches the response from the previous `requestDiff` calls if the file did not change
-      // so we can safely call it here without concerns for performance.
-      const diffResponse = await this.#workspaceDiff?.requestDiff(modifiedUISourceCode);
-      return {
-        diff: diffResponse?.diff,
-        uiSourceCode: modifiedUISourceCode,
-      };
-    }));
+    const uiSourceCodeAndDiffs = (await Promise.all(this.#modifiedUISourceCodes.map(async modifiedUISourceCode => {
+                                   // `requestDiff` caches the response from the previous `requestDiff` calls if the file did not change
+                                   // so we can safely call it here without concerns for performance.
+                                   const diffResponse = await this.#workspaceDiff?.requestDiff(modifiedUISourceCode);
+                                   if (!diffResponse || diffResponse.diff.length === 0) {
+                                     return;
+                                   }
+
+                                   return {
+                                     diff: diffResponse.diff,
+                                     uiSourceCode: modifiedUISourceCode,
+                                   };
+                                 }))).filter(uiSourceCodeAndDiff => !!uiSourceCodeAndDiff);
 
     const singleDiffViewInputs =
-        uiSourceCodeAndDiffs.filter(uiSourceCodeAndDiff => Boolean(uiSourceCodeAndDiff.diff))
+        uiSourceCodeAndDiffs
             .map(({uiSourceCode, diff}) => {
               let displayText = uiSourceCode.fullDisplayName();
               // If the UISourceCode is backed by a workspace, we show the path as "{workspace-name}/path/relative/to/workspace"
@@ -203,7 +207,7 @@ export class CombinedDiffView extends UI.Widget.Widget {
                 ].join('/');
               }
               return {
-                diff: diff as Diff.Diff.DiffArray,  // We already filter above the ones that does not have `diff`.
+                diff,
                 fileName: `${uiSourceCode.isDirty() ? '*' : ''}${displayText}`,
                 fileUrl: uiSourceCode.url(),
                 mimeType: uiSourceCode.mimeType(),

front_end/third_party/diff/DiffWrapper.ts

@@ -28,6 +28,11 @@ export const DiffWrapper = {
     const text1 = lines1.map(line => idMap.toChar(line)).join('');
     const text2 = lines2.map(line => idMap.toChar(line)).join('');
 
+    // If both text are the same don't emit a diff
+    if(text1 === text2){
+      return [];
+    }
+
     const diff = DiffWrapper.charDiff(text1, text2);
     const lineDiff = [];
     for (let i = 0; i < diff.length; i++) {

front_end/ui/components/diff_view/DiffView.test.ts

@@ -71,3 +71,17 @@ describeWithLocale('DiffView', () => {
     assert.isNotNull(view.querySelector('.diff-line-spacer'));
   });
 });
+
+describe('DiffWrapper', () => {
+  describe('lineDiff', () => {
+    it('should work with no changes', () => {
+      let diff = Diff.Diff.DiffWrapper.lineDiff([''], ['']);
+
+      assert.deepEqual(diff, []);
+
+      diff = Diff.Diff.DiffWrapper.lineDiff(['initial'], ['initial']);
+
+      assert.deepEqual(diff, []);
+    });
+  });
+});