Bug 1504464 - Part 2: Mark reader.[[closedPromise]] as handled in reader.releaseLock(). r=jwalden

In this case, it's likely the user doesn't see this as an error at all.

Differential Revision: https://phabricator.services.mozilla.com/D14497

--HG--
extra : moz-landing-system : lando

js/src/builtin/Stream.cpp

@@ -2119,19 +2119,20 @@ static MOZ_MUST_USE bool ReadableStreamReaderGenericRelease(
 
   // Step 3: If reader.[[ownerReadableStream]].[[state]] is "readable", reject
   //         reader.[[closedPromise]] with a TypeError exception.
+  Rooted<PromiseObject*> unwrappedClosedPromise(cx);
   if (unwrappedStream->readable()) {
-    Rooted<PromiseObject*> closedPromise(
-        cx, UnwrapInternalSlot<PromiseObject>(
-                cx, unwrappedReader, ReadableStreamReader::Slot_ClosedPromise));
-    if (!closedPromise) {
+    unwrappedClosedPromise = 
+      UnwrapInternalSlot<PromiseObject>(
+        cx, unwrappedReader, ReadableStreamReader::Slot_ClosedPromise);
+    if (!unwrappedClosedPromise) {
       return false;
     }
 
-    AutoRealm ar(cx, closedPromise);
+    AutoRealm ar(cx, unwrappedClosedPromise);
     if (!cx->compartment()->wrap(cx, &exn)) {
       return false;
     }
-    if (!PromiseObject::reject(cx, closedPromise, exn)) {
+    if (!PromiseObject::reject(cx, unwrappedClosedPromise, exn)) {
       return false;
     }
   } else {
@@ -2141,6 +2142,7 @@ static MOZ_MUST_USE bool ReadableStreamReaderGenericRelease(
     if (!closedPromise) {
       return false;
     }
+    unwrappedClosedPromise = &closedPromise->as<PromiseObject>();
 
     AutoRealm ar(cx, unwrappedReader);
     if (!cx->compartment()->wrap(cx, &closedPromise)) {
@@ -2149,10 +2151,14 @@ static MOZ_MUST_USE bool ReadableStreamReaderGenericRelease(
     unwrappedReader->setClosedPromise(closedPromise);
   }
 
-  // Step 5: Set reader.[[ownerReadableStream]].[[reader]] to undefined.
+  // Step 5: Set reader.[[closedPromise]].[[PromiseIsHandled]] to true.
+  unwrappedClosedPromise->setHandled();
+  cx->runtime()->removeUnhandledRejectedPromise(cx, unwrappedClosedPromise);
+
+  // Step 6: Set reader.[[ownerReadableStream]].[[reader]] to undefined.
   unwrappedStream->clearReader();
 
-  // Step 6: Set reader.[[ownerReadableStream]] to undefined.
+  // Step 7: Set reader.[[ownerReadableStream]] to undefined.
   unwrappedReader->clearStream();
 
   return true;

js/src/jit-test/tests/stream/reader-closedPromise-handled-2.js

@@ -0,0 +1,33 @@
+// Releasing a reader should not result in a promise being tracked as
+// unhandled.
+
+function test(readable) {
+  // Create an errored stream.
+  let controller;
+  let stream = new ReadableStream({
+    start(c) {
+      controller = c;
+    }
+  });
+  drainJobQueue();
+
+  // Track promises.
+  let status = new Map;
+  setPromiseRejectionTrackerCallback((p, x) => { status.set(p, x); });
+
+  // Per Streams spec 3.7.5 step 5, this creates a rejected promise
+  // (reader.closed) but marks it as handled.
+  let reader = stream.getReader();
+  if (!readable) {
+    controller.close();
+  }
+  reader.releaseLock();
+
+  // Check that the promise's status is not 0 (unhandled);
+  // it may be either 1 (handled) or undefined (never tracked).
+  let result = status.get(reader.closed);
+  assertEq(result === 1 || result === undefined, true);
+}
+
+test(true);
+test(false);