stream: make Broadcast.from() only return the Broadcast

Signed-off-by: James M Snell <jasnell@gmail.com>
Assisted-by: Opencode
PR-URL: https://github.com/nodejs/node/pull/66030
Reviewed-By: Filip Skokan <panva.ip@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

doc/api/stream_iter.md

@@ -1374,7 +1374,8 @@ added:
 
 * `input` {AsyncIterable|Iterable|BroadcastChannel}
 * `options` {Object} Same as `broadcast()`.
-* Returns: {Object} `{ writer, broadcast }`
+* Returns: {BroadcastChannel|Object} A `broadcastProtocol` input returns its
+  {BroadcastChannel} directly. Other inputs return `{ writer, broadcast }`.
 
 Create a {BroadcastChannel} from an existing source. The source is consumed
 automatically and pushed to all subscribers.
@@ -1883,7 +1884,7 @@ class MessageBus {
 }
 
 const bus = new MessageBus();
-const { broadcast } = Broadcast.from(bus);
+const broadcast = Broadcast.from(bus);
 const consumer = broadcast.push();
 bus.send('hello');
 bus.close();
@@ -1919,7 +1920,7 @@ class MessageBus {
 }
 
 const bus = new MessageBus();
-const { broadcast } = Broadcast.from(bus);
+const broadcast = Broadcast.from(bus);
 const consumer = broadcast.push();
 bus.send('hello');
 bus.close();

lib/internal/streams/iter/broadcast.js

@@ -923,7 +923,7 @@ const Broadcast = {
         throw new ERR_INVALID_RETURN_VALUE(
           'an object', '[Symbol.for(\'Stream.broadcastProtocol\')]', bc);
       }
-      return { __proto__: null, writer: { __proto__: null }, broadcast: bc };
+      return bc;
     }
 
     const source = from(input);

test/parallel/test-stream-iter-broadcast-from.js

@@ -181,6 +181,15 @@ async function testBroadcastFromSourceError() {
 // Protocol validation
 // =============================================================================
 
+function testBroadcastProtocolReturnsBroadcast() {
+  const { broadcast: expected } = broadcast();
+  const obj = {
+    [Symbol.for('Stream.broadcastProtocol')]() { return expected; },
+  };
+  assert.strictEqual(Broadcast.from(obj), expected);
+  expected.cancel();
+}
+
 function testBroadcastProtocolReturnsNull() {
   const obj = {
     [Symbol.for('Stream.broadcastProtocol')]() { return null; },
@@ -223,6 +232,7 @@ Promise.all([
   testAlreadyAbortedSignal(),
   testBroadcastFromCancelWhileBlocked(),
   testBroadcastFromSourceError(),
+  testBroadcastProtocolReturnsBroadcast(),
   testBroadcastProtocolReturnsNull(),
   testBroadcastProtocolReturnsString(),
   testBroadcastProtocolReturnsUndefined(),

test/parallel/test-stream-iter-property-access.js

@@ -140,8 +140,7 @@ async function testMultiConsumerProtocolsSnapshotMethods() {
   const broadcastTarget = broadcast().broadcast;
   const broadcastFixture = protocolFixture(
     broadcastProtocol, broadcastTarget);
-  assert.strictEqual(
-    Broadcast.from(broadcastFixture.input).broadcast, broadcastTarget);
+  assert.strictEqual(Broadcast.from(broadcastFixture.input), broadcastTarget);
   assert.strictEqual(broadcastFixture.accesses, 1);
 
   const shareTarget = share('abc');