Make stdout|stderr properties undefined instead of null

index.js

@@ -110,8 +110,12 @@ function handleInput(spawned, input) {
 }
 
 function handleOutput(options, value) {
-	if (value && options.stripFinalNewline) {
-		value = stripFinalNewline(value);
+	if (typeof value !== 'string' && !Buffer.isBuffer(value)) {
+		return;
+	}
+
+	if (options.stripFinalNewline) {
+		return stripFinalNewline(value);
 	}
 
 	return value;

test.js

@@ -51,6 +51,20 @@ test('stdout/stderr/all available on errors', async t => {
 	t.is(typeof error.all, 'string');
 });
 
+test('stdout/stderr/all are undefined if ignored', async t => {
+	const {stdout, stderr, all} = await execa('noop', {stdio: 'ignore'});
+	t.is(stdout, undefined);
+	t.is(stderr, undefined);
+	t.is(all, undefined);
+});
+
+test('stdout/stderr/all are undefined if ignored in sync mode', t => {
+	const {stdout, stderr, all} = execa.sync('noop', {stdio: 'ignore'});
+	t.is(stdout, undefined);
+	t.is(stderr, undefined);
+	t.is(all, undefined);
+});
+
 test('pass `stdout` to a file descriptor', async t => {
 	const file = tempfile('.txt');
 	await execa('fixtures/noop', ['foo bar'], {stdout: fs.openSync(file, 'w')});