R: Add snapshot tests for indentation (#2577)

extensions/positron-r/src/test/README.md

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+Launch tests by running this from the repository root:
+
+```sh
+yarn test-extension -l positron-r
+```

extensions/positron-r/src/test/editor-utils.ts

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+// From testUtils.ts in the typescript-language-feature extension
+// https://github.com/posit-dev/positron/blob/main/extensions/typescript-language-features/src/test/testUtils.ts
+
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as fs from 'fs';
+import * as os from 'os';
+import { join } from 'path';
+import * as vscode from 'vscode';
+
+export function rndName() {
+	let name = '';
+	const possible = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
+	for (let i = 0; i < 10; i++) {
+		name += possible.charAt(Math.floor(Math.random() * possible.length));
+	}
+	return name;
+}
+
+export function createRandomFile(contents = '', fileExtension = 'txt'): Thenable<vscode.Uri> {
+	return new Promise((resolve, reject) => {
+		const tmpFile = join(os.tmpdir(), rndName() + '.' + fileExtension);
+		fs.writeFile(tmpFile, contents, (error) => {
+			if (error) {
+				return reject(error);
+			}
+
+			resolve(vscode.Uri.file(tmpFile));
+		});
+	});
+}
+
+export function deleteFile(file: vscode.Uri): Thenable<boolean> {
+	return new Promise((resolve, reject) => {
+		fs.unlink(file.fsPath, (err) => {
+			if (err) {
+				reject(err);
+			} else {
+				resolve(true);
+			}
+		});
+	});
+}
+
+export const CURSOR = '"<>"';
+
+export async function withFileEditor(
+	contents: string,
+	fileExtension: string,
+	run: (editor: vscode.TextEditor, doc: vscode.TextDocument) => Promise<void>
+): Promise<void> {
+	const cursorIndex = contents.indexOf(CURSOR);
+	const rawContents = contents.replace(CURSOR, '');
+
+	const file = await createRandomFile(rawContents, fileExtension);
+
+	try {
+		const doc = await vscode.workspace.openTextDocument(file);
+		const editor = await vscode.window.showTextDocument(doc);
+
+		if (cursorIndex >= 0) {
+			const pos = doc.positionAt(cursorIndex);
+			editor.selection = new vscode.Selection(pos, pos);
+		}
+
+		await run(editor, doc);
+
+		if (doc.isDirty) {
+			await doc.save();
+		}
+	} finally {
+		deleteFile(file);
+	}
+}
+
+export const onDocumentChange = (doc: vscode.TextDocument): Promise<vscode.TextDocument> => {
+	return new Promise<vscode.TextDocument>(resolve => {
+		const sub = vscode.workspace.onDidChangeTextDocument(e => {
+			if (e.document !== doc) {
+				return;
+			}
+			sub.dispose();
+			resolve(e.document);
+		});
+	});
+};
+
+export const type = async (document: vscode.TextDocument, text: string): Promise<vscode.TextDocument> => {
+	const onChange = onDocumentChange(document);
+	await vscode.commands.executeCommand('type', { text });
+	await onChange;
+	return document;
+};

extensions/positron-r/src/test/indentation.test.ts

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+import * as vscode from 'vscode';
+import * as assert from 'assert';
+import * as fs from 'fs';
+import { CURSOR, type, withFileEditor } from './editor-utils';
+import { EXTENSION_ROOT_DIR } from '../constants';
+import { removeLeadingLines } from '../util';
+
+const snapshotsFolder = `${EXTENSION_ROOT_DIR}/src/test/snapshots`;
+const snippetsPath = `${snapshotsFolder}/indentation-cases.R`;
+const snapshotsPath = `${snapshotsFolder}/indentation-snapshots.R`;
+
+// FIXME: This should normally be run as part of tests setup in `before()` but
+// it's somehow not defined
+async function init() {
+	// Open workspace with custom configuration for snapshots. If you need
+	// custom settings set them there via `config.update()`.
+	const uri = vscode.Uri.file(snapshotsFolder);
+	await vscode.commands.executeCommand('vscode.openFolder', uri, false);
+	const config = vscode.workspace.getConfiguration();
+
+	// Prevents `ENOENT: no such file or directory` errors caused by us
+	// deleting temporary editor files befor Code had the opportunity to
+	// save the user history of these files.
+	config.update('workbench.localHistory.enabled', false, vscode.ConfigurationTarget.Workspace);
+}
+
+suite('Indentation', () => {
+	// This regenerates snapshots in place. If the snapshots differ from last
+	// run, a failure is emitted. You can either commit the new output or discard
+	// it if that's a bug to fix.
+	test('Regenerate and check', async () => {
+		await init();
+		const expected = fs.readFileSync(snapshotsPath, 'utf8');
+		const current = await regenerateIndentSnapshots();
+
+		// Update snapshot file
+		fs.writeFileSync(snapshotsPath, current, 'utf8');
+
+		// Notify if snapshots were outdated
+		assert.strictEqual(expected, current);
+	});
+});
+
+async function regenerateIndentSnapshots() {
+	const snippets = fs.
+		readFileSync(snippetsPath, 'utf8').
+		split('# ---\n');
+
+	// Remove documentation snippet
+	snippets.splice(0, 1);
+
+	const snapshots: string[] = ['# File generated from `indentation-cases.R`.\n\n'];
+
+	for (const snippet of snippets) {
+		const bareSnippet = snippet.split('\n').slice(0, -1).join('\n');
+
+		await withFileEditor(snippet, 'R', async (_editor, doc) => {
+			// Type one newline character to trigger indentation
+			await type(doc, `\n${CURSOR}`);
+			const snapshot = removeLeadingLines(doc.getText(), /^$|^#/);
+			snapshots.push(bareSnippet + '\n# ->\n' + snapshot);
+		});
+	}
+
+	return snapshots.join('# ---\n');
+}

extensions/positron-r/src/test/snapshots/.vscode/settings.json

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+{
+    "workbench.localHistory.enabled": false
+}

extensions/positron-r/src/test/snapshots/indentation-cases.R

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+# Indentation snapshots. Edit cases in `indentation-cases.R` and observe results
+# in `indentation-snapshots.R`.
+#
+# The cursor position is represented by a string containing angular brackets. A
+# newline is typed at that position, triggering indentation rules. The result is
+# saved in the snapshot file.
+#
+# Snippets are separated by `# ---`. This makes it possible to extract them and
+# process them separately to prevent interferences between test cases.
+
+# ---
+1 +"<>"
+
+# ---
+1 +
+	2 +"<>"
+
+# ---
+data |>"<>"
+
+# ---
+data |>
+	fn()"<>"
+
+# ---
+# https://github.com/posit-dev/positron/issues/1727
+# FIXME
+data |>
+	fn()
+"<>"
+
+# ---
+# https://github.com/posit-dev/positron/issues/1316
+data |>
+	fn() |>"<>"
+
+# ---
+# With trailing whitespace
+# https://github.com/posit-dev/positron/pull/1655#issuecomment-1780093395
+data |>
+	fn() |> "<>"
+
+# ---
+data |>
+	fn1() |>
+	fn2() |>"<>"
+
+# ---
+# FIXME
+data |>
+	fn1() |>
+	fn2(
+		"arg"
+	)"<>"
+
+# ---
+# https://github.com/posit-dev/positron-beta/discussions/46
+# FIXME
+data |>
+	fn("<>")
+
+# ---
+# FIXME
+{
+	fn(function() {}"<>")
+}
+
+# ---
+# FIXME
+{
+	fn(function() {
+		#
+	}"<>")
+}
+
+# ---
+for (i in NA) NULL"<>"
+
+# ---
+# https://github.com/posit-dev/positron/issues/1880
+# FIXME
+for (i in 1) fn()"<>"