From 0391515f78051f647388db8acc62d1fe655af415 Mon Sep 17 00:00:00 2001
From: Robert Nagy <ronagy@icloud.com>
Date: Sat, 11 Jul 2020 23:50:09 +0200
Subject: [PATCH 1/2] 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
---
 lib/_stream_transform.js              | 22 ++++++++++++++++++++--
 test/parallel/test-stream-pipeline.js | 24 ++++++++++++++++++++++++
 2 files changed, 44 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/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);
+    }),
+  );
+}

From 0e5a7d549f1e49f65914c292d56a3b2246c59cfa Mon Sep 17 00:00:00 2001
From: Robert Nagy <ronagy@icloud.com>
Date: Sun, 12 Jul 2020 00:25:11 +0200
Subject: [PATCH 2/2] fixup

---
 lib/zlib.js | 5 +++++
 1 file changed, 5 insertions(+)

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