From 17bcea458b7f98ffeed96cc89db07a23396489b8 Mon Sep 17 00:00:00 2001
From: Jason Simmons <jason-simmons@users.noreply.github.com>
Date: Wed, 2 Nov 2022 19:14:38 -0700
Subject: [PATCH] Enter a scope before calling Dart APIs in
 ThrowIfUIOperationsProhibited (flutter/engine#37226)

---
 engine/src/flutter/lib/ui/ui_dart_state.cc        |  1 +
 engine/src/flutter/testing/dart/isolate_test.dart | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/engine/src/flutter/lib/ui/ui_dart_state.cc b/engine/src/flutter/lib/ui/ui_dart_state.cc
index c478c760aa..df5f74bd46 100644
--- a/engine/src/flutter/lib/ui/ui_dart_state.cc
+++ b/engine/src/flutter/lib/ui/ui_dart_state.cc
@@ -97,6 +97,7 @@ void UIDartState::DidSetIsolate() {
 
 void UIDartState::ThrowIfUIOperationsProhibited() {
   if (!UIDartState::Current()->IsRootIsolate()) {
+    Dart_EnterScope();
     Dart_ThrowException(
         tonic::ToDart("UI actions are only available on root isolate."));
   }
diff --git a/engine/src/flutter/testing/dart/isolate_test.dart b/engine/src/flutter/testing/dart/isolate_test.dart
index 87a8081a1a..c3330fb29d 100644
--- a/engine/src/flutter/testing/dart/isolate_test.dart
+++ b/engine/src/flutter/testing/dart/isolate_test.dart
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:isolate';
+import 'dart:ui';
 
 import 'package:litetest/litetest.dart';
 
@@ -20,4 +21,14 @@ void main() {
     }
     expect(threw, true);
   });
+
+  test('UI isolate API throws in a background isolate', () async {
+    void callUiApi(void message) {
+      PlatformDispatcher.instance.onReportTimings = (_) {};
+    }
+    final ReceivePort errorPort = ReceivePort();
+    await Isolate.spawn<void>(callUiApi, null, onError: errorPort.sendPort);
+    final List<dynamic> isolateError = await errorPort.first as List<dynamic>;
+    expect(isolateError[0], 'UI actions are only available on root isolate.');
+  });
 }