From a65218f5e82eabdeb4018d80f64e6456f47f9f34 Mon Sep 17 00:00:00 2001
From: Robert Nagy <ronagy@icloud.com>
Date: Sat, 11 Jul 2020 23:50:09 +0200
Subject: [PATCH] stream: try to wait for flush to complete before 'finish'

Due to compat reasons Transform streams don't always wait
for flush to complete before finishing the stream.

Try to wait when possible, i.e. when the user does not
override _final.

Fixes: https://github.com/nodejs/node/issues/34274

PR-URL: https://github.com/nodejs/node/pull/34314
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Zeyu Yang <himself65@outlook.com>
---
 lib/_stream_transform.js              | 22 ++++++++++++++++++++--
 lib/zlib.js                           |  5 +++++
 test/parallel/test-stream-pipeline.js | 24 ++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/lib/_stream_transform.js b/lib/_stream_transform.js
index a27b09887b9e3e..564cdf0e82a986 100644
--- a/lib/_stream_transform.js
+++ b/lib/_stream_transform.js
@@ -106,11 +106,15 @@ function Transform(options) {
   this.on('prefinish', prefinish);
 }
 
-function prefinish() {
+function final(cb) {
   if (typeof this._flush === 'function' && !this.destroyed) {
     this._flush((er, data) => {
       if (er) {
-        this.destroy(er);
+        if (cb) {
+          cb(er);
+        } else {
+          this.destroy(er);
+        }
         return;
       }
 
@@ -118,12 +122,26 @@ function prefinish() {
         this.push(data);
       }
       this.push(null);
+      if (cb) {
+        cb();
+      }
     });
   } else {
     this.push(null);
+    if (cb) {
+      cb();
+    }
+  }
+}
+
+function prefinish() {
+  if (this._final !== final) {
+    final.call(this);
   }
 }
 
+Transform.prototype._final = final;
+
 Transform.prototype._transform = function(chunk, encoding, callback) {
   throw new ERR_METHOD_NOT_IMPLEMENTED('_transform()');
 };
diff --git a/lib/zlib.js b/lib/zlib.js
index 7cc8e2e6275041..fc8e378f41feb5 100644
--- a/lib/zlib.js
+++ b/lib/zlib.js
@@ -323,6 +323,11 @@ ZlibBase.prototype._flush = function(callback) {
   this._transform(Buffer.alloc(0), '', callback);
 };
 
+// Force Transform compat behavior.
+ZlibBase.prototype._final = function(callback) {
+  callback();
+};
+
 // If a flush is scheduled while another flush is still pending, a way to figure
 // out which one is the "stronger" flush is needed.
 // This is currently only used to figure out which flush flag to use for the
diff --git a/test/parallel/test-stream-pipeline.js b/test/parallel/test-stream-pipeline.js
index 5077aaa11a4e6b..5d3f34f51e85be 100644
--- a/test/parallel/test-stream-pipeline.js
+++ b/test/parallel/test-stream-pipeline.js
@@ -1231,3 +1231,27 @@ const net = require('net');
     assert.strictEqual(res, 'helloworld');
   }));
 }
+
+{
+  let flushed = false;
+  const makeStream = () =>
+    new Transform({
+      transform: (chunk, enc, cb) => cb(null, chunk),
+      flush: (cb) =>
+        setTimeout(() => {
+          flushed = true;
+          cb(null);
+        }, 1),
+    });
+
+  const input = new Readable();
+  input.push(null);
+
+  pipeline(
+    input,
+    makeStream(),
+    common.mustCall(() => {
+      assert.strictEqual(flushed, true);
+    }),
+  );
+}