Fix reject option with early spawning errors (#734)

index.js

@@ -134,15 +134,16 @@ export function execa(rawFile, rawArgs, rawOptions) {
 	} catch (error) {
 		// Ensure the returned error is always both a promise and a child process
 		const dummySpawned = new childProcess.ChildProcess();
-		const errorPromise = Promise.reject(makeError({
+		const errorInstance = makeError({
 			error,
 			stdio: Array.from({length: stdioStreamsGroups.length}),
 			command,
 			escapedCommand,
 			options,
 			timedOut: false,
 			isCanceled: false,
-		}));
+		});
+		const errorPromise = options.reject ? Promise.reject(errorInstance) : Promise.resolve(errorInstance);
 		mergePromise(dummySpawned, errorPromise);
 		return dummySpawned;
 	}
@@ -219,7 +220,7 @@ export function execaSync(rawFile, rawArgs, rawOptions) {
 	try {
 		result = childProcess.spawnSync(file, args, options);
 	} catch (error) {
-		throw makeError({
+		const errorInstance = makeError({
 			error,
 			stdio: Array.from({length: stdioStreamsGroups.stdioLength}),
 			command,
@@ -228,6 +229,12 @@ export function execaSync(rawFile, rawArgs, rawOptions) {
 			timedOut: false,
 			isCanceled: false,
 		});
+
+		if (!options.reject) {
+			return errorInstance;
+		}
+
+		throw errorInstance;
 	}
 
 	pipeOutputSync(stdioStreamsGroups, result);

test/error.js

@@ -50,7 +50,7 @@ test('empty error.stdio[0] even with input', async t => {
 const SPAWN_ERROR_CODES = new Set(['EINVAL', 'ENOTSUP', 'EPERM']);
 
 test('stdout/stderr/stdio on process spawning errors', async t => {
-	const {code, stdout, stderr, stdio} = await t.throwsAsync(execa('noop.js', {uid: -1}));
+	const {code, stdout, stderr, stdio} = await t.throwsAsync(execa('empty.js', {uid: -1}));
 	t.true(SPAWN_ERROR_CODES.has(code));
 	t.is(stdout, undefined);
 	t.is(stderr, undefined);
@@ -59,7 +59,7 @@ test('stdout/stderr/stdio on process spawning errors', async t => {
 
 test('stdout/stderr/all/stdio on process spawning errors - sync', t => {
 	const {code, stdout, stderr, stdio} = t.throws(() => {
-		execaSync('noop.js', {uid: -1});
+		execaSync('empty.js', {uid: -1});
 	});
 	t.true(SPAWN_ERROR_CODES.has(code));
 	t.is(stdout, undefined);

test/test.js

@@ -153,27 +153,40 @@ test('execa() returns a promise with pid', async t => {
 	await subprocess;
 });
 
-test('child_process.spawn() propagated errors have correct shape', t => {
-	const subprocess = execa('noop.js', {uid: -1});
+const testEarlyErrorShape = async (t, reject) => {
+	const subprocess = execa('', {reject});
 	t.notThrows(() => {
 		subprocess.catch(() => {});
 		subprocess.unref();
 		subprocess.on('error', () => {});
 	});
+};
+
+test('child_process.spawn() early errors have correct shape', testEarlyErrorShape, true);
+test('child_process.spawn() early errors have correct shape - reject false', testEarlyErrorShape, false);
+
+test('child_process.spawn() early errors are propagated', async t => {
+	const {failed} = await t.throwsAsync(execa(''));
+	t.true(failed);
 });
 
-test('child_process.spawn() errors are propagated', async t => {
-	const {failed} = await t.throwsAsync(execa('noop.js', {uid: -1}));
+test('child_process.spawn() early errors are returned', async t => {
+	const {failed} = await execa('', {reject: false});
 	t.true(failed);
 });
 
-test('child_process.spawnSync() errors are propagated with a correct shape', t => {
+test('child_process.spawnSync() early errors are propagated with a correct shape', t => {
 	const {failed} = t.throws(() => {
-		execaSync('noop.js', {uid: -1});
+		execaSync('');
 	});
 	t.true(failed);
 });
 
+test('child_process.spawnSync() early errors are propagated with a correct shape - reject false', t => {
+	const {failed} = execaSync('', {reject: false});
+	t.true(failed);
+});
+
 test('do not try to consume streams twice', async t => {
 	const subprocess = execa('noop.js', ['foo']);
 	const {stdout} = await subprocess;