child_process: preserve argument type

A previous fix for a `maxBuffer` bug resulted in a change to the
argument type for the `data` event on `child.stdin` and `child.stdout`
when using `child_process.exec()`.

This fixes the `maxBuffer` bug in a way that does not have that side
effect.

PR-URL: https://github.com/nodejs/node/pull/7391
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Jackson Tian <shyvo1987@gmail.com>
Fixes: https://github.com/nodejs/node/issues/7342
Refs: https://github.com/nodejs/node/issues/1901

1 files changed, 23 insertions, 0 deletions

diff --git a/test/parallel/test-child-process-exec-stdout-stderr-data-string.js b/test/parallel/test-child-process-exec-stdout-stderr-data-string.js
new file mode 100644
index 0000000000..8ab834c98f
--- /dev/null
+++ b/test/parallel/test-child-process-exec-stdout-stderr-data-string.js
@@ -0,0 +1,23 @@
+'use strict';
+// Refs: https://github.com/nodejs/node/issues/7342
+const common = require('../common');
+const assert = require('assert');
+const exec = require('child_process').exec;
+
+var stdoutCalls = 0;
+var stderrCalls = 0;
+
+const command = common.isWindows ? 'dir' : 'ls';
+exec(command).stdout.on('data', (data) => {
+  stdoutCalls += 1;
+});
+
+exec('fhqwhgads').stderr.on('data', (data) => {
+  assert.strictEqual(typeof data, 'string');
+  stderrCalls += 1;
+});
+
+process.on('exit', () => {
+  assert(stdoutCalls > 0);
+  assert(stderrCalls > 0);
+});