From 1cefb7e710f6bb1c6f13d000d1525bc25b83bb06 Mon Sep 17 00:00:00 2001
From: Momtchil Momtchev <momtchil@momtchev.com>
Date: Sun, 22 Nov 2020 19:01:23 +0100
Subject: [PATCH] stream: fix regression on duplex end

Decide the return status of writeOrBuffer before
calling stream.write which can reset state.length

Add unit test for #35926

Refs: https://github.com/nodejs/node/issues/35926

Backport-PR-URL: https://github.com/nodejs/node/pull/36375
PR-URL: https://github.com/nodejs/node/pull/35941
Fixes: https://github.com/nodejs/node/issues/35926
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
---
 lib/internal/streams/writable.js              | 12 +++----
 .../test-stream-duplex-readable-end.js        | 32 +++++++++++++++++++
 2 files changed, 38 insertions(+), 6 deletions(-)
 create mode 100644 test/parallel/test-stream-duplex-readable-end.js

diff --git a/lib/internal/streams/writable.js b/lib/internal/streams/writable.js
index 209fa4a25413af..fbc0532681b83d 100644
--- a/lib/internal/streams/writable.js
+++ b/lib/internal/streams/writable.js
@@ -336,6 +336,12 @@ function writeOrBuffer(stream, state, chunk, encoding, callback) {
 
   state.length += len;
 
+  // stream._write resets state.length
+  const ret = state.length < state.highWaterMark;
+  // We must ensure that previous needDrain will not be reset to false.
+  if (!ret)
+    state.needDrain = true;
+
   if (state.writing || state.corked || state.errored) {
     state.buffered.push({ chunk, encoding, callback });
     if (state.allBuffers && encoding !== 'buffer') {
@@ -353,12 +359,6 @@ function writeOrBuffer(stream, state, chunk, encoding, callback) {
     state.sync = false;
   }
 
-  const ret = state.length < state.highWaterMark;
-
-  // We must ensure that previous needDrain will not be reset to false.
-  if (!ret)
-    state.needDrain = true;
-
   // Return false if errored or destroyed in order to break
   // any synchronous while(stream.write(data)) loops.
   return ret && !state.errored && !state.destroyed;
diff --git a/test/parallel/test-stream-duplex-readable-end.js b/test/parallel/test-stream-duplex-readable-end.js
new file mode 100644
index 00000000000000..ca3ccf63c49474
--- /dev/null
+++ b/test/parallel/test-stream-duplex-readable-end.js
@@ -0,0 +1,32 @@
+'use strict';
+// https://github.com/nodejs/node/issues/35926
+require('../common');
+const assert = require('assert');
+const stream = require('stream');
+
+let loops = 5;
+
+const src = new stream.Readable({
+  read() {
+    if (loops--)
+      this.push(Buffer.alloc(20000));
+  }
+});
+
+const dst = new stream.Transform({
+  transform(chunk, output, fn) {
+    this.push(null);
+    fn();
+  }
+});
+
+src.pipe(dst);
+
+function parser_end() {
+  assert.ok(loops > 0);
+  dst.removeAllListeners();
+}
+
+dst.on('data', () => { });
+dst.on('end', parser_end);
+dst.on('error', parser_end);