From 6c468df9af5bfce9291e93402a2f35c42aa780ab Mon Sep 17 00:00:00 2001
From: Brian White <mscdex@mscdex.net>
Date: Tue, 2 Feb 2016 01:50:34 -0500
Subject: [PATCH] child_process: fix data loss with readable event

This commit prevents child process stdio streams from being
automatically flushed on child process exit/close if a 'readable'
event handler has been attached at the time of exit.

Without this, child process stdio data can be lost if the process
exits quickly and a `read()` (e.g. from a 'readable' handler)
hasn't had the chance to get called yet.

Fixes: https://github.com/nodejs/node/issues/5034
PR-URL: https://github.com/nodejs/node/pull/5037
Reviewed-By: James M Snell <jasnell@gmail.com>
---
 lib/child_process.js                          |  7 +++++--
 test/simple/test-child-process-flush-stdio.js | 17 +++++++++++++++++
 2 files changed, 22 insertions(+), 2 deletions(-)
 create mode 100644 test/simple/test-child-process-flush-stdio.js

diff --git a/lib/child_process.js b/lib/child_process.js
index bc1a909fdc4562..9bb64e64b66cf3 100644
--- a/lib/child_process.js
+++ b/lib/child_process.js
@@ -1094,8 +1094,11 @@ util.inherits(ChildProcess, EventEmitter);
 function flushStdio(subprocess) {
   if (subprocess.stdio == null) return;
   subprocess.stdio.forEach(function(stream, fd, stdio) {
-    if (!stream || !stream.readable || stream._consuming ||
-        stream._readableState.flowing)
+    if (!stream ||
+        !stream.readable ||
+        stream._consuming ||
+        stream._readableState.flowing ||
+        stream._readableState.readableListening)
       return;
     stream.resume();
   });
diff --git a/test/simple/test-child-process-flush-stdio.js b/test/simple/test-child-process-flush-stdio.js
new file mode 100644
index 00000000000000..b5140860813c2b
--- /dev/null
+++ b/test/simple/test-child-process-flush-stdio.js
@@ -0,0 +1,17 @@
+'use strict';
+var cp = require('child_process');
+var common = require('../common');
+var assert = require('assert');
+
+var buffer = [];
+var p = cp.spawn('echo', ['123']);
+p.on('close', common.mustCall(function(code, signal) {
+  assert.strictEqual(code, 0);
+  assert.strictEqual(signal, null);
+  assert.strictEqual(Buffer.concat(buffer).toString().trim(), '123');
+}));
+p.stdout.on('readable', function() {
+  var buf;
+  while (buf = this.read())
+    buffer.push(buf);
+});