fixup! stream: pass ERR_STREAM_WRITE_AFTER_END to .end(cb) after end

The previous version always synthesized ERR_STREAM_WRITE_AFTER_END
when kEnding was set, which broke test-stream-writable-end-cb-error
block 1: a writable whose underlying _write errors with `_err`, and
whose `.end(cb1)` and `.end(cb2)` are both expected to receive that
underlying error via kOnFinished.

Tighten the condition to only synthesize WRITE_AFTER_END when the
stream has no in-flight write (kWriting), no buffered data
(kBuffered), no stored error (kErrored), and an empty buffer length.
In any of those cases there is real pending state that will surface a
meaningful error through the existing kOnFinished cascade, so the cb
should be queued and receive that real error instead.

Signed-off-by: Maruthan G <[email protected]>

Author: maruthang

lib/internal/streams/writable.js

@@ -845,13 +845,15 @@ Writable.prototype.end = function(chunk, encoding, cb) {
     err = new ERR_STREAM_ALREADY_FINISHED('end');
   } else if ((state[kState] & kDestroyed) !== 0) {
     err = new ERR_STREAM_DESTROYED('end');
-  } else if ((state[kState] & kEnding) !== 0 && typeof cb === 'function') {
-    // The stream is already ending (or ended) but not yet finished or
-    // destroyed. For consistency with `.write(chunk, cb)` after end (which
-    // invokes cb with ERR_STREAM_WRITE_AFTER_END), surface the same error
-    // through the user-supplied callback. Note: we do not call
-    // errorOrDestroy here in order to preserve the pre-existing forgiving
-    // behavior of `.end()` (no cb) called multiple times.
+  } else if ((state[kState] & kEnding) !== 0 && typeof cb === 'function' &&
+             (state[kState] & (kErrored | kWriting | kBuffered)) === 0 &&
+             state.length === 0) {
+    // The stream is already ending and has no in-flight write, buffered
+    // data, or stored error that would surface a real error to the user.
+    // Synthesize ERR_STREAM_WRITE_AFTER_END so the user-supplied callback
+    // fires consistently with `.write(chunk, cb)` after end. When pending
+    // work or a stored error exists, fall through so the cb is queued on
+    // kOnFinished and receives that real error instead.
     err = new ERR_STREAM_WRITE_AFTER_END();
   }