Fix commenting on added files in the Commits tree

src/test/view/treeNodes/gitFileChangeNode.test.ts

@@ -0,0 +1,92 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { default as assert } from 'assert';
+import * as vscode from 'vscode';
+import { GitChangeType } from '../../../common/file';
+import { toReviewUri } from '../../../common/uri';
+import { GitFileChangeModel } from '../../../view/fileChangeModel';
+import { GitFileChangeNode } from '../../../view/treeNodes/fileChangeNode';
+import { TreeNodeParent } from '../../../view/treeNodes/treeNode';
+
+function disposable(): vscode.Disposable {
+	return { dispose: () => { } };
+}
+
+const rootUri = vscode.Uri.file('/root');
+const commitSha = '1111111111111111111111111111111111111111';
+const headSha = '2222222222222222222222222222222222222222';
+
+describe('GitFileChangeNode', function () {
+	const parent: TreeNodeParent = {
+		reveal: async () => { },
+		refresh: () => { },
+		children: undefined,
+		view: { visible: true, onDidChangeVisibility: () => disposable() } as unknown as vscode.TreeView<any>,
+	} as unknown as TreeNodeParent;
+
+	const pullRequest = {
+		number: 1,
+		head: { sha: headSha },
+		fileChangeViewedState: {},
+		reviewThreadsCache: [],
+		onDidChangeReviewThreads: () => disposable(),
+		onDidChangeFileViewedState: () => disposable(),
+	};
+
+	const folderRepositoryManager = {
+		repository: { rootUri },
+		setFileViewedContext: () => { },
+	};
+
+	/**
+	 * A file node as created for a commit in the Commits tree: the paths are `review` uris carrying
+	 * the sha of that commit, and the node opens a diff instead of the workspace file.
+	 */
+	function createCommitFileNode(fileName: string, status: GitChangeType): GitFileChangeNode {
+		const uri = vscode.Uri.parse(`commit~11111111/${fileName}`);
+		const changeModel = new GitFileChangeModel(
+			folderRepositoryManager as any,
+			pullRequest as any,
+			{ status, fileName, blobUrl: undefined },
+			toReviewUri(uri, fileName, undefined, commitSha, true, { base: false }, rootUri),
+			toReviewUri(uri, fileName, undefined, commitSha, true, { base: true }, rootUri),
+			commitSha,
+		);
+
+		const node = new GitFileChangeNode(parent, folderRepositoryManager as any, pullRequest as any, changeModel);
+		node.useViewChangesCommand();
+		return node;
+	}
+
+	it('diffs an added file against the head side of the change', async function () {
+		// The head side has to be `filePath`. With `parentFilePath` the document is the base of the
+		// diff, and commenting ranges for the base of an added file are always empty, so it isn't
+		// possible to comment on a file added by the commit being viewed.
+		const node = createCommitFileNode('data/added.json', GitChangeType.ADD);
+
+		await node.resolve();
+
+		assert.strictEqual(node.command.command, 'vscode.diff');
+		const [left, right] = node.command.arguments as vscode.Uri[];
+		assert.strictEqual(right.toString(), node.changeModel.filePath.toString());
+		assert.notStrictEqual(right.toString(), node.changeModel.parentFilePath.toString());
+		// The base side is the empty document, so the whole file reads as added.
+		assert.deepStrictEqual(JSON.parse(left.query), { path: null, commit: null });
+	});
+
+	it('diffs a deleted file against the base side of the change', async function () {
+		// The content of a deleted file only exists in the base, so unlike the added case the base
+		// side is the one holding the document.
+		const node = createCommitFileNode('data/deleted.json', GitChangeType.DELETE);
+
+		await node.resolve();
+
+		assert.strictEqual(node.command.command, 'vscode.diff');
+		const [left, right] = node.command.arguments as vscode.Uri[];
+		assert.strictEqual(left.toString(), node.changeModel.parentFilePath.toString());
+		assert.deepStrictEqual(JSON.parse(right.query), { path: null, commit: null });
+	});
+});

src/view/treeNodes/fileChangeNode.ts

@@ -349,12 +349,16 @@ export class GitFileChangeNode extends FileChangeNode implements vscode.TreeItem
 				}),
 			});
 
+			// For added files the content lives on the head side of the diff, so use `filePath`.
+			// Using `parentFilePath` here would make the commenting range provider treat the
+			// document as the base, where an added file has no deleted lines and therefore no
+			// commenting ranges at all.
 			return {
 				command: 'vscode.diff',
 				arguments:
 					this.status === GitChangeType.DELETE
 						? [this.changeModel.parentFilePath, emptyFileUri, `${this.fileName}`, {}]
-						: [emptyFileUri, this.changeModel.parentFilePath, `${this.fileName}`, {}],
+						: [emptyFileUri, this.changeModel.filePath, `${this.fileName}`, {}],
 				title: 'Open Diff',
 			};
 		}