Show one pane for peeks with one meaningful side

apps/review-desktop/code-oss/src/vs/review/browser/reviewChangedFilesTree.test.ts

@@ -55,7 +55,7 @@ test('a viewed file says "Viewed" in place of its counts', () => {
 
 test('a file with changes left to read shows its remaining counts, not greyed', () => {
 	const unread = row('unread');
-	assert.equal(unread.counts, '+3−0');
+	assert.equal(unread.counts, '+3');
 	assert.ok(!unread.row.classList.contains('review-file-folded'));
 	assert.ok(!unread.row.classList.contains('review-file-viewed'));
 });

apps/review-desktop/code-oss/src/vs/review/browser/reviewChangedFilesTree.ts

@@ -174,8 +174,8 @@ export class ChangedFilesTreeRenderer
 			else if (progress?.state === 'viewed') template.counts.textContent = 'Viewed';
 			else if (progress?.state === 'folded') template.counts.textContent = 'Folded';
 			else if (additions !== undefined && deletions !== undefined) {
-				const added = append(template.counts, $('span.review-tree-added')); added.textContent = `+${compact(additions)}`;
-				const removed = append(template.counts, $('span.review-tree-removed')); removed.textContent = `−${compact(deletions)}`;
+				if (additions) append(template.counts, $('span.review-tree-added')).textContent = `+${compact(additions)}`;
+				if (deletions) append(template.counts, $('span.review-tree-removed')).textContent = `−${compact(deletions)}`;
 			}
 			const total = progress?.total ?? { additions: lines?.added ?? 0, deletions: lines?.removed ?? 0 };
 			if (!binary) template.countsTooltip.content = element.file.status === "unchanged"

apps/review-desktop/code-oss/src/vs/review/services/reviewFilesDiffView.ts

@@ -11,11 +11,12 @@ import { Orientation, SplitView } from "../../base/browser/ui/splitview/splitvie
 import { disposableTimeout } from "../../base/common/async.js";
 import { Emitter, Event } from "../../base/common/event.js";
 import { Disposable, DisposableStore, MutableDisposable, toDisposable } from "../../base/common/lifecycle.js";
-import { autorun, observableValue } from "../../base/common/observable.js";
+import { autorun, observableFromEvent, observableValue } from "../../base/common/observable.js";
 import { isEqual } from "../../base/common/resources.js";
 import { URI } from "../../base/common/uri.js";
 import { ElementSizeObserver } from "../../editor/browser/config/elementSizeObserver.js";
 import { isDiffEditor, type IDiffEditor } from "../../editor/browser/editorBrowser.js";
+import { DiffEditorViewModel } from "../../editor/browser/widget/diffEditor/diffEditorViewModel.js";
 import { MultiDiffEditorViewModel } from "../../editor/browser/widget/multiDiffEditor/multiDiffEditorViewModel.js";
 import { MultiDiffEditorWidget, type RevealOptions } from "../../editor/browser/widget/multiDiffEditor/multiDiffEditorWidget.js";
 import type { IMultiDiffEditorViewState } from "../../editor/browser/widget/multiDiffEditor/multiDiffEditorWidgetImpl.js";
@@ -195,10 +196,10 @@ export class ReviewFilesDiffView extends Disposable {
 	private pendingViewState: IMultiDiffEditorViewState | undefined;
 	private viewModel: MultiDiffEditorViewModel | undefined;
 	private input: ReviewFilesEditorInput | undefined;
-	private readonly applyLayout: () => void;
 	private readonly readyFiles = new Set<string>();
 	private readonly fileStates = new Map<string, string>();
 	private readonly settleHold = this._register(new MutableDisposable<DisposableStore>());
+	private readonly documentLayout = this._register(new MutableDisposable());
 	/** Full structural counts for views without persisted coverage. */
 	private readonly streamStats = new Map<
 		string,
@@ -225,7 +226,7 @@ export class ReviewFilesDiffView extends Disposable {
 	constructor(
 		private readonly container: HTMLElement,
 		overflowWidgetsDomNode: HTMLElement | undefined,
-		layout: ReviewDiffLayoutSetting,
+		private readonly diffLayout: ReviewDiffLayoutSetting,
 		private readonly fileTreeContainer: HTMLElement | undefined,
 		private readonly onToggleViewed: ((path: string, sectionId?: string) => void) | undefined,
 		private readonly onToggleSection: ((id: string) => void) | undefined,
@@ -301,11 +302,9 @@ export class ReviewFilesDiffView extends Disposable {
 		);
 		// The widget's own switch, not the per-item option refresh: it pins the
 		// width heuristic off, so the chosen layout is what renders at any width.
-		// A document snippet of an unchanged file reads as plain code.
-		this.applyLayout = () => this.widget.setRenderSideBySide(layout.get() === "split"
-			&& !(this.document && this.input?.entries.every(entry => entry.file.status === "unchanged")));
-		this._register(layout.onDidChange(this.applyLayout));
-		this.applyLayout();
+		const applyLayout = () => this.widget.setRenderSideBySide(this.diffLayout.get() === "split");
+		if (!document) this._register(this.diffLayout.onDidChange(applyLayout));
+		applyLayout();
 		if (document) {
 			this._register(this.widget.onDidChangeContentHeight(() => {
 				const height = Math.max(40, this.widget.getContentHeight());
@@ -388,13 +387,30 @@ export class ReviewFilesDiffView extends Disposable {
 
 	async setInput(input: ReviewFilesEditorInput, viewState: IMultiDiffEditorViewState | undefined): Promise<void> {
 		this.settleHold.clear();
+		this.documentLayout.clear();
 		this.pendingViewState = viewState;
 		this.input = input;
-		this.applyLayout();
 		this.changedFilesTree?.setFiles(Array.from(new Map(input.entries.map(entry => [entry.file.path, entry.file])).values()));
 		const viewModel = await input.getViewModel();
 		if (this._store.isDisposed) return;
 		this.viewModel = viewModel;
+		if (this.document) {
+			const preference = observableFromEvent(this.diffLayout.onDidChange, () => this.diffLayout.get());
+			// Unchanged and one-sided files, and completed identical comparisons, override the user's layout.
+			this.documentLayout.value = autorun(reader => {
+				const items = viewModel.items.read(reader);
+				const onePane = items.length > 0 && items.every(item => {
+					const entry = input.entries.find(entry => sameResource(item.originalUri, entry.original) && sameResource(item.modifiedUri, entry.modified));
+					if (!entry || entry.file.binary) return false;
+					if (entry.file.status === "added" || entry.file.status === "deleted" || entry.file.status === "unchanged") return true;
+					const comparison = item.diffEditorViewModel;
+					if (!(comparison instanceof DiffEditorViewModel)) return false;
+					const diff = comparison.diff.read(reader);
+					return comparison.isDiffUpToDate.read(reader) && diff?.identical === true && !diff.quitEarly;
+				});
+				this.widget.setRenderSideBySide(preference.read(reader) === "split" && !onePane);
+			});
+		}
 		// The canvas mounts this view without a user gesture, so the widget's
 		// first-change navigation must never take keyboard focus.
 		this.widget.setViewModel(viewModel, { preserveFocus: true, viewState, initialScrollPosition: this.document ? "top" : "firstChange" });

apps/review-desktop/code-oss/src/vs/review/services/reviewMultiDiff.ts

@@ -207,19 +207,25 @@ export class ReviewMultiDiffUIElementFactory
 				deletions.textContent = `−${compactCount(current.deletions!)}`;
           counts.setAttribute(
             "aria-label",
-            `${current.additions} lines added, ${current.deletions} lines removed`,
+            [current.additions ? `${current.additions} lines added` : "", current.deletions ? `${current.deletions} lines removed` : ""].filter(Boolean).join(", "),
           );
         }
 			countsTooltip.content = current.countsTooltip;
+			const settled = current.viewedState === "viewed" || current.viewedState === "folded";
+			additions.hidden = deletions.hidden = false;
 			const path = current.modified ?? current.original;
 			viewed.update(current.viewedState, `${current.viewedScope === 'lens' ? 'selected lens in ' : ''}${path ? reviewMultiDiffLabelPath(path) : 'file'}`, !current.onToggleViewed);
-			counts.classList.toggle("review-counts-viewed", current.viewedState === "viewed" || current.viewedState === "folded");
+			counts.classList.toggle("review-counts-viewed", settled);
 			counts.classList.toggle("review-counts-folded", current.viewedState === "folded");
 			if (current.viewedState === "viewed") { additions.textContent = current.viewedScope === 'lens' ? 'Lens viewed' : 'Viewed'; deletions.textContent = ""; }
 			else if (current.viewedState === "folded") {
 				// A hidden file's note already says why it is folded.
 				additions.textContent = "Folded"; deletions.textContent = "";
 				counts.hidden ||= !!current.note;
+			} else {
+				additions.hidden = !current.additions;
+				deletions.hidden = !current.deletions;
+				counts.hidden ||= additions.hidden && deletions.hidden;
 			}
 
 			note.hidden = !current.note;