Adds detection for yarn, and '--no-yarn' to suppress detection

src/main.ts

@@ -61,7 +61,8 @@ module.exports = function (argv: string[]): void {
 	program
 		.command('ls')
 		.description('Lists all the files that will be published')
-		.option('--yarn', 'Use yarn instead of npm')
+		.option('--yarn', 'Use yarn instead of npm (default inferred from presense of yarn.lock or .yarnrc)')
+		.option('--no-yarn', 'Use npm instead of yarn (default inferred from lack of yarn.lock or .yarnrc)')
 		.option(
 			'--packagedDependencies <path>',
 			'Select packages that should be published only (includes dependencies)',
@@ -83,7 +84,8 @@ module.exports = function (argv: string[]): void {
 		)
 		.option('--baseContentUrl [url]', 'Prepend all relative links in README.md with this url.')
 		.option('--baseImagesUrl [url]', 'Prepend all relative image links in README.md with this url.')
-		.option('--yarn', 'Use yarn instead of npm')
+		.option('--yarn', 'Use yarn instead of npm (default inferred from presense of yarn.lock or .yarnrc)')
+		.option('--no-yarn', 'Use npm instead of yarn (default inferred from lack of yarn.lock or .yarnrc)')
 		.option('--ignoreFile [path]', 'Indicate alternative .vscodeignore')
 		.option('--noGitHubIssueLinking', 'Prevent automatic expansion of GitHub-style issue syntax into links')
 		.option(
@@ -117,7 +119,8 @@ module.exports = function (argv: string[]): void {
 		)
 		.option('--baseContentUrl [url]', 'Prepend all relative links in README.md with this url.')
 		.option('--baseImagesUrl [url]', 'Prepend all relative image links in README.md with this url.')
-		.option('--yarn', 'Use yarn instead of npm while packing extension files')
+		.option('--yarn', 'Use yarn instead of npm (default inferred from presense of yarn.lock or .yarnrc)')
+		.option('--no-yarn', 'Use npm instead of yarn (default inferred from lack of yarn.lock or .yarnrc)')
 		.option('--noVerify')
 		.option('--ignoreFile [path]', 'Indicate alternative .vscodeignore')
 		.option(

src/npm.ts

@@ -181,7 +181,10 @@ async function getYarnProductionDependencies(cwd: string, packagedDependencies?:
 async function getYarnDependencies(cwd: string, packagedDependencies?: string[]): Promise<string[]> {
 	const result: string[] = [cwd];
 
-	if (await new Promise(c => fs.exists(path.join(cwd, 'yarn.lock'), c))) {
+	// Using 'existsSync' instead of 'exists' since 'exists' is deprecated. While 'fs.existsSync'
+	// is a blocking IO operation, this won't affect the CLI as every code path that calls
+	// 'getYarnDependencies' essentially blocks the CLI anyways while waiting for `exists` to complete.
+	if (fs.existsSync(path.join(cwd, 'yarn.lock'))) {
 		const deps = await getYarnProductionDependencies(cwd, packagedDependencies);
 		const flatten = (dep: YarnDependency) => {
 			result.push(dep.path);

src/package.ts

@@ -984,7 +984,7 @@ const defaultIgnore = [
 	'**/.vscode-test/**',
 ];
 
-function collectAllFiles(cwd: string, useYarn = false, dependencyEntryPoints?: string[]): Promise<string[]> {
+function collectAllFiles(cwd: string, useYarn = detectYarn(cwd), dependencyEntryPoints?: string[]): Promise<string[]> {
 	return getDependencies(cwd, useYarn, dependencyEntryPoints).then(deps => {
 		const promises: Promise<string[]>[] = deps.map(dep => {
 			return glob('**', { cwd: dep, nodir: true, dot: true, ignore: 'node_modules/**' }).then(files =>
@@ -998,7 +998,7 @@ function collectAllFiles(cwd: string, useYarn = false, dependencyEntryPoints?: s
 
 function collectFiles(
 	cwd: string,
-	useYarn = false,
+	useYarn = detectYarn(cwd),
 	dependencyEntryPoints?: string[],
 	ignoreFile?: string
 ): Promise<string[]> {
@@ -1084,7 +1084,7 @@ export function createDefaultProcessors(manifest: Manifest, options: IPackageOpt
 
 export function collect(manifest: Manifest, options: IPackageOptions = {}): Promise<IFile[]> {
 	const cwd = options.cwd || process.cwd();
-	const useYarn = options.useYarn || false;
+	const useYarn = options.useYarn === undefined ? detectYarn(cwd) : options.useYarn;
 	const packagedDependencies = options.dependencyEntryPoints || undefined;
 	const ignoreFile = options.ignoreFile || undefined;
 	const processors = createDefaultProcessors(manifest, options);
@@ -1124,14 +1124,14 @@ function getDefaultPackageName(manifest: Manifest): string {
 	return `${manifest.name}-${manifest.version}.vsix`;
 }
 
-async function prepublish(cwd: string, manifest: Manifest, useYarn: boolean = false): Promise<void> {
+async function prepublish(cwd: string, manifest: Manifest, useYarn: boolean = detectYarn(cwd)): Promise<void> {
 	if (!manifest.scripts || !manifest.scripts['vscode:prepublish']) {
 		return;
 	}
 
 	console.log(`Executing prepublish script '${useYarn ? 'yarn' : 'npm'} run vscode:prepublish'...`);
 
-	await new Promise((c, e) => {
+	await new Promise<void>((c, e) => {
 		const tool = useYarn ? 'yarn' : 'npm';
 		const child = cp.spawn(tool, ['run', 'vscode:prepublish'], { cwd, shell: true, stdio: 'inherit' });
 		child.on('exit', code => (code === 0 ? c() : e(`${tool} failed with exit code ${code}`)));
@@ -1157,6 +1157,16 @@ async function getPackagePath(cwd: string, manifest: Manifest, options: IPackage
 	}
 }
 
+function detectYarn(cwd: string) {
+	for (const file of ["yarn.lock", ".yarnrc"]) {
+		if (fs.existsSync(path.join(cwd, file))) {
+			console.log(`Detected presense of ${file}. Using 'yarn' instead of 'npm' (to override this pass '--no-yarn' on the command line).`);
+			return true;
+		}
+	}
+	return false;
+}
+
 export async function pack(options: IPackageOptions = {}): Promise<IPackageResult> {
 	const cwd = options.cwd || process.cwd();
 
@@ -1202,7 +1212,7 @@ export async function packageCommand(options: IPackageOptions = {}): Promise<any
  */
 export function listFiles(
 	cwd = process.cwd(),
-	useYarn = false,
+	useYarn = detectYarn(cwd),
 	packagedDependencies?: string[],
 	ignoreFile?: string
 ): Promise<string[]> {
@@ -1214,7 +1224,7 @@ export function listFiles(
  */
 export function ls(
 	cwd = process.cwd(),
-	useYarn = false,
+	useYarn = detectYarn(cwd),
 	packagedDependencies?: string[],
 	ignoreFile?: string
 ): Promise<void> {

src/test/package.test.ts

@@ -209,6 +209,23 @@ describe('collect', function () {
 			});
 	});
 
+	it('should detect yarn', () => {
+		const cwd = fixture('packagedDependencies');
+
+		return readManifest(cwd)
+			.then(manifest => collect(manifest, { cwd, dependencyEntryPoints: ['isexe'] }))
+			.then(files => {
+				let seenWhich: boolean;
+				let seenIsexe: boolean;
+				files.forEach(file => {
+					seenWhich = file.path.indexOf('/node_modules/which/') >= 0;
+					seenIsexe = file.path.indexOf('/node_modules/isexe/') >= 0;
+				});
+				assert.equal(seenWhich, false);
+				assert.equal(seenIsexe, true);
+			});
+	});
+
 	it('should include all node_modules when dependencyEntryPoints is not defined', () => {
 		const cwd = fixture('packagedDependencies');