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>

1 files changed, 20 insertions, 2 deletions

diff --git a/lib/_stream_transform.js b/lib/_stream_transform.js
index a27b09887b..564cdf0e82 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()');
 };