[dartdevc] Fixing issue whereby async generators would not resume properly after yielding from within a catch block.

Presubmits at cl/297164263

Fixes #39994

Change-Id: I2fff5db716f1b3e4f125ec9ae5f018a7edbbed67
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/136846
Reviewed-by: Lasse R.H. Nielsen <lrn@google.com>
Commit-Queue: Mark Zhou <markzipan@google.com>

sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart

@@ -305,10 +305,7 @@ class _AsyncStarImpl<T> {
     // already be scheduled. This will cause at least one more iteration to
     // run (adding another data item to the Stream) before actually pausing.
     // It could be fixed by moving the `isPaused` check inside `runBody`.
-    if (isScheduled ||
-        controller.isPaused ||
-        isSuspendedAtYieldStar ||
-        isSuspendedAtAwait) {
+    if (isScheduled || controller.isPaused || isSuspendedAtYieldStar) {
       return;
     }
     isScheduled = true;

sdk_nnbd/lib/_internal/js_dev_runtime/patch/async_patch.dart

@@ -303,10 +303,7 @@ class _AsyncStarImpl<T> {
     // already be scheduled. This will cause at least one more iteration to
     // run (adding another data item to the Stream) before actually pausing.
     // It could be fixed by moving the `isPaused` check inside `runBody`.
-    if (isScheduled ||
-        controller.isPaused ||
-        isSuspendedAtYieldStar ||
-        isSuspendedAtAwait) {
+    if (isScheduled || controller.isPaused || isSuspendedAtYieldStar) {
       return;
     }
     isScheduled = true;

tests/language/async_star/yield_from_catch_test.dart

@@ -0,0 +1,33 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Test for issue: https://github.com/dart-lang/sdk/issues/39994
+
+import "dart:async";
+import "package:expect/expect.dart";
+import "package:async_helper/async_helper.dart";
+
+Stream<String> testStream() async* {
+  try {
+    await testThrow();
+    yield "A";
+  } catch (e) {
+    yield "B";
+    yield "C";
+    yield "D";
+  }
+}
+
+testThrow() async {
+  throw Exception();
+}
+
+test() async {
+  var result = await testStream().toList();
+  Expect.listEquals(["B", "C", "D"], result);
+}
+
+main() {
+  asyncTest(test);
+}

tests/language_2/async_star/yield_from_catch_test.dart

@@ -0,0 +1,33 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Test for issue: https://github.com/dart-lang/sdk/issues/39994
+
+import "dart:async";
+import "package:expect/expect.dart";
+import "package:async_helper/async_helper.dart";
+
+Stream<String> testStream() async* {
+  try {
+    await testThrow();
+    yield "A";
+  } catch (e) {
+    yield "B";
+    yield "C";
+    yield "D";
+  }
+}
+
+testThrow() async {
+  throw Exception();
+}
+
+test() async {
+  var result = await testStream().toList();
+  Expect.listEquals(["B", "C", "D"], result);
+}
+
+main() {
+  asyncTest(test);
+}