Add test on handling broken promises in AsyncGenerator.prototype.return (#3472)

* Add test on handling broken promises in AsyncGenerator.prototype.return

* fixup!

* fixup!

test/built-ins/AsyncGeneratorPrototype/return/return-state-completed-broken-promise.js

@@ -0,0 +1,62 @@
+// Copyright (C) 2022 Chengzhong Wu. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-asyncgenerator-prototype-return
+description: >
+  A broken promise should reject the returned promise of
+  AsyncGenerator.prototype.return when the generator is completed.
+info: |
+  AsyncGenerator.prototype.return ( value )
+  ...
+  8. If state is either suspendedStart or completed, then
+    a. Set generator.[[AsyncGeneratorState]] to awaiting-return.
+    b. Perform ! AsyncGeneratorAwaitReturn(generator).
+  ...
+
+  AsyncGeneratorAwaitReturn ( generator )
+  ...
+  6. Let promise be Completion(PromiseResolve(%Promise%, completion.[[Value]])).
+  7. If promiseCompletion is an abrupt completion, then
+    a. Set generator.[[AsyncGeneratorState]] to completed.
+    b. Perform AsyncGeneratorCompleteStep(generator, promiseCompletion, true).
+    c. Perform AsyncGeneratorDrainQueue(generator).
+    d. Return unused.
+  8. Assert: promiseCompletion.[[Type]] is normal.
+  9. Let promise be promiseCompletion.[[Value]].
+  ...
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+let unblock;
+let blocking = new Promise(resolve => { unblock = resolve; });
+let unblocked = false;
+var g = async function*() {
+  await blocking;
+  unblocked = true;
+};
+
+var it = g();
+let brokenPromise = Promise.resolve(42);
+Object.defineProperty(brokenPromise, 'constructor', {
+  get: function () {
+    throw new Error('broken promise');
+  }
+});
+
+it.next();
+it.return(brokenPromise)
+  .then(
+    () => {
+      throw new Test262Error("Expected rejection");
+    },
+    err => {
+      assert(unblocked, false, 'return should be rejected before generator is resumed');
+      assert.sameValue(err.message, 'broken promise');
+    }
+  )
+  .then($DONE, $DONE);
+
+unblock();

test/built-ins/AsyncGeneratorPrototype/return/return-suspendedStart-broken-promise.js

@@ -0,0 +1,54 @@
+// Copyright (C) 2022 Chengzhong Wu. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-asyncgenerator-prototype-return
+description: >
+  A broken promise should reject the returned promise of
+  AsyncGenerator.prototype.return when the generator's state is suspendedStart.
+info: |
+  AsyncGenerator.prototype.return ( value )
+  ...
+  8. If state is either suspendedStart or completed, then
+    a. Set generator.[[AsyncGeneratorState]] to awaiting-return.
+    b. Perform AsyncGeneratorAwaitReturn(_generator_).
+  ...
+
+  AsyncGeneratorAwaitReturn ( generator )
+  ...
+  6. Let promise be Completion(PromiseResolve(%Promise%, completion.[[Value]])).
+  7. If promiseCompletion is an abrupt completion, then
+    a. Set generator.[[AsyncGeneratorState]] to completed.
+    b. Perform AsyncGeneratorCompleteStep(generator, promiseCompletion, true).
+    c. Perform AsyncGeneratorDrainQueue(generator).
+    d. Return unused.
+  8. Assert: promiseCompletion.[[Type]] is normal.
+  9. Let promise be promiseCompletion.[[Value]].
+  ...
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var g = async function*() {
+  throw new Test262Error('Generator must not be resumed.');
+};
+
+var it = g();
+let brokenPromise = Promise.resolve(42);
+Object.defineProperty(brokenPromise, 'constructor', {
+  get: function () {
+    throw new Error('broken promise');
+  }
+});
+
+it.return(brokenPromise)
+  .then(
+    () => {
+      throw new Test262Error("Expected rejection");
+    },
+    err => {
+      assert.sameValue(err.message, 'broken promise');
+    }
+  )
+  .then($DONE, $DONE);

test/built-ins/AsyncGeneratorPrototype/return/return-suspendedYield-broken-promise-try-catch.js

@@ -0,0 +1,64 @@
+// Copyright (C) 2022 Chengzhong Wu. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-asyncgenerator-prototype-return
+description: >
+  A broken promise should resume the generator and reject with
+  the exception when the generator's state is suspendedYield.
+info: |
+  AsyncGenerator.prototype.return ( value )
+  ...
+  9. Else if state is suspendedYield, then
+    a. Perform AsyncGeneratorResume(generator, completion).
+  ...
+
+  AsyncGeneratorCompleteStep ( generator, completion, done [ , realm ] )
+  Resumes the steps defined at AsyncGeneratorStart ( generator, generatorBody )
+  ...
+  4. Set the code evaluation state of genContext such that when evaluation is resumed for that execution context the following steps will be performed:
+    ...
+    i. Perform AsyncGeneratorDrainQueue(generator).
+    j. Return undefined.
+
+  AsyncGeneratorDrainQueue ( generator )
+  ...
+  5. Repeat, while done is false,
+    a. Let next be the first element of queue.
+    b. Let completion be Completion(next.[[Completion]]).
+    c. If completion.[[Type]] is return, then
+        i. Set generator.[[AsyncGeneratorState]] to awaiting-return.
+        ii. Perform AsyncGeneratorAwaitReturn(generator).
+        iii. Set done to true.
+  ...
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+let caughtErr;
+var g = async function*() {
+  try {
+    yield;
+    return 'this is never returned';
+  } catch (err) {
+    caughtErr = err;
+    return 1;
+  }
+};
+
+let brokenPromise = Promise.resolve(42);
+Object.defineProperty(brokenPromise, 'constructor', {
+  get: function () {
+    throw new Error('broken promise');
+  }
+});
+
+var it = g();
+it.next().then(() => {
+  return it.return(brokenPromise);
+}).then(ret => {
+  assert.sameValue(caughtErr.message, 'broken promise');
+  assert.sameValue(ret.value, 1, 'returned value');
+  assert.sameValue(ret.done, true, 'iterator is closed');
+}).then($DONE, $DONE);