stream: preserve push signal abort reason

Pass the stream-wide signal reason directly to writer.fail() so valid
non-Error abort reasons are not replaced with an AbortError.
Signed-off-by: Kamat, Trivikram <16024985+trivikr@users.noreply.github.com>
Assisted-by: codex:gpt-5.6-sol
PR-URL: #64798Fixes: #64797
Reviewed-By: Aviv Keller <me@aviv.sh>

Author: trivikr

lib/internal/streams/iter/push.js

@@ -25,7 +25,7 @@ const {
 ERR_INVALID_STATE,
 },
 }=require('internal/errors');
-const{isError,lazyDOMException }=require('internal/util');
+const{ lazyDOMException }=require('internal/util');
 const{
  validateAbortSignal,
  validateInteger,
@@ -135,9 +135,7 @@ class PushQueue {
 
 if(this.#signal){
 this.#abortHandler =()=>{
-this.fail(isError(this.#signal.reason) ?
-this.#signal.reason :
-lazyDOMException('Aborted','AbortError'));
+this.fail(this.#signal.reason);
 };
 onSignalAbort(this.#signal,this.#abortHandler);
 }

test/parallel/test-stream-iter-push-basic.js

@@ -107,6 +107,16 @@ async function testAbortSignal() {
 );
 }
 
+asyncfunctiontestAbortSignalReason(){
+constreason='test reason';
+constac=newAbortController();
+const{ writer }=push({signal: ac.signal});
+
+ac.abort(reason);
+
+awaitassert.rejects(writer.write('data'),(err)=>err===reason);
+}
+
 asyncfunctiontestPreAbortedSignal(){
 const{ readable }=push({signal: AbortSignal.abort()});
 awaitassert.rejects(async()=>{
@@ -172,6 +182,7 @@ Promise.all([
 testWriterFail(),
 testConsumerBreak(),
 testAbortSignal(),
+testAbortSignalReason(),
 testPreAbortedSignal(),
 testConsumerBreakWriteSyncReturnsFalse(),
 testPushWithTransforms(),