stream: implement throw for async iterator

PR-URL: #31316
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Minwoo Jung <nodecorelab@gmail.com>

Author: ronag

lib/internal/streams/async_iterator.js

@@ -71,6 +71,31 @@ function wrapForNext(lastPromise, iter) {
 constAsyncIteratorPrototype=ObjectGetPrototypeOf(
 ObjectGetPrototypeOf(asyncfunction*(){}).prototype);
 
+functionfinish(self,err){
+returnnewPromise((resolve,reject)=>{
+conststream=self[kStream];
+
+// TODO(ronag): Remove this check once finished() handles
+// already ended and/or destroyed streams.
+constended=stream.destroyed||stream.readableEnded||
+(stream._readableState&&stream._readableState.endEmitted);
+
+if(ended){
+resolve(createIterResult(undefined,true));
+return;
+}
+
+finished(stream,(err)=>{
+if(err&&err.code!=='ERR_STREAM_PREMATURE_CLOSE'){
+reject(err);
+}else{
+resolve(createIterResult(undefined,true));
+}
+});
+destroy(stream,err);
+});
+}
+
 constReadableStreamAsyncIteratorPrototype=ObjectSetPrototypeOf({
 getstream(){
 returnthis[kStream];
@@ -131,27 +156,11 @@ const ReadableStreamAsyncIteratorPrototype = ObjectSetPrototypeOf({
 },
 
 return(){
-returnnewPromise((resolve,reject)=>{
-conststream=this[kStream];
-
-// TODO(ronag): Remove this check once finished() handles
-// already ended and/or destroyed streams.
-constended=stream.destroyed||stream.readableEnded||
-(stream._readableState&&stream._readableState.endEmitted);
-if(ended){
-resolve(createIterResult(undefined,true));
-return;
-}
+returnfinish(this);
+},
 
-finished(stream,(err)=>{
-if(err&&err.code!=='ERR_STREAM_PREMATURE_CLOSE'){
-reject(err);
-}else{
-resolve(createIterResult(undefined,true));
-}
-});
-destroy(stream);
-});
+throw(err){
+returnfinish(this,err);
 },
 },AsyncIteratorPrototype);
 

test/parallel/test-stream-readable-async-iterators.js

@@ -282,6 +282,28 @@ async function tests() {
 assert.strictEqual(received,1);
 }
 
+{
+// Iterator throw.
+
+constreadable=newReadable({
+objectMode: true,
+read(){
+this.push('hello');
+}
+});
+
+readable.on('error',common.mustCall((err)=>{
+assert.strictEqual(err.message,'kaboom');
+}));
+
+constit=readable[Symbol.asyncIterator]();
+it.throw(newError('kaboom')).catch(common.mustCall((err)=>{
+assert.strictEqual(err.message,'kaboom');
+}));
+
+assert.strictEqual(readable.destroyed,true);
+}
+
 {
 console.log('destroyed by throw');
 constreadable=newReadable({