From 62b12ad2b612d0359770448f2834f4ae5828cc20 Mon Sep 17 00:00:00 2001
From: Felix Kling <felix.kling@gmx.net>
Date: Fri, 30 Nov 2018 16:56:51 -0800
Subject: [PATCH] Respect process.stdout.write's return value

Docs: https://nodejs.org/api/stream.html#stream_writable_write_chunk_encoding_callback

If we continue to write to stdout (or stderr for that matter), without
respecting the return value of the `write` method, output might get
interleaved incorrectly, which breaks tools that do something with
jscodeshift's output.
---
 src/Runner.js | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/src/Runner.js b/src/Runner.js
index 7d54d1b8..3977d947 100644
--- a/src/Runner.js
+++ b/src/Runner.js
@@ -26,18 +26,39 @@ function lineBreak(str) {
   return /\n$/.test(str) ? str : str + '\n';
 }
 
+const bufferedWrite = (function() {
+  const buffer = [];
+  let buffering = false;
+
+  process.stdout.on('drain', () => {
+    if (!buffering) return;
+    while (buffer.length > 0 && process.stdout.write(buffer.shift()) !== false);
+    if (buffer.length === 0) {
+      buffering = false;
+    }
+  });
+  return function write(msg) {
+    if (buffering) {
+      buffer.push(msg);
+    }
+    if (process.stdout.write(msg) === false) {
+      buffering = true;
+    }
+  };
+}());
+
 const log = {
   ok(msg, verbose) {
-    verbose >= 2 && process.stdout.write(colors.white.bgGreen(' OKK ') + msg);
+    verbose >= 2 && bufferedWrite(colors.white.bgGreen(' OKK ') + msg);
   },
   nochange(msg, verbose) {
-    verbose >= 1 && process.stdout.write(colors.white.bgYellow(' NOC ') + msg);
+    verbose >= 1 && bufferedWrite(colors.white.bgYellow(' NOC ') + msg);
   },
   skip(msg, verbose) {
-    verbose >= 1 && process.stdout.write(colors.white.bgYellow(' SKIP ') + msg);
+    verbose >= 1 && bufferedWrite(colors.white.bgYellow(' SKIP ') + msg);
   },
   error(msg, verbose) {
-    verbose >= 0 && process.stdout.write(colors.white.bgRed(' ERR ') + msg);
+    verbose >= 0 && bufferedWrite(colors.white.bgRed(' ERR ') + msg);
   },
 };