From 94fa5f4edf3b822cdc8a94a4dc87a28274642830 Mon Sep 17 00:00:00 2001
From: Chris Yang <ychris@google.com>
Date: Mon, 10 Apr 2023 20:45:27 -0700
Subject: [PATCH] [ios] fix background crash when FlutterViewController is
 destroyed after engine destroyed context (flutter/engine#41037)

[ios] fix background crash when FlutterViewController is destroyed after engine destroyed context
---
 .../ios/framework/Source/FlutterEngine.mm     |  2 +-
 .../ScenariosTests/FlutterEngineTest.m        | 38 +++++++++++++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterEngine.mm b/engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterEngine.mm
index 422a6155e40..f434b9305bc 100644
--- a/engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterEngine.mm
+++ b/engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterEngine.mm
@@ -434,7 +434,7 @@ static constexpr int kNumProfilerSamplesPerSec = 5;
   _undoManagerPlugin.get().viewController = nil;
   if (!_allowHeadlessExecution) {
     [self destroyContext];
-  } else {
+  } else if (_shell) {
     flutter::PlatformViewIOS* platform_view = [self iosPlatformView];
     if (platform_view) {
       platform_view->SetOwnerViewController({});
diff --git a/engine/src/flutter/testing/scenario_app/ios/Scenarios/ScenariosTests/FlutterEngineTest.m b/engine/src/flutter/testing/scenario_app/ios/Scenarios/ScenariosTests/FlutterEngineTest.m
index 3c9119af617..218bc780a9b 100644
--- a/engine/src/flutter/testing/scenario_app/ios/Scenarios/ScenariosTests/FlutterEngineTest.m
+++ b/engine/src/flutter/testing/scenario_app/ios/Scenarios/ScenariosTests/FlutterEngineTest.m
@@ -12,6 +12,8 @@
 
 @implementation FlutterEngineTest
 
+extern NSNotificationName const FlutterViewControllerWillDealloc;
+
 - (void)testIsolateId {
   FlutterEngine* engine = [[FlutterEngine alloc] initWithName:@"test" project:nil];
   XCTAssertNil(engine.isolateId);
@@ -48,4 +50,40 @@
   XCTAssertNil(engine.lifecycleChannel);
 }
 
+// https://github.com/flutter/flutter/issues/123776
+- (void)testReleaseViewControllerAfterDestroyContextInHeadlessMode {
+  FlutterEngine* engine = [[FlutterEngine alloc] initWithName:@"test"
+                                                      project:nil
+                                       allowHeadlessExecution:YES];
+  XCTAssertNil(engine.navigationChannel);
+  XCTAssertNil(engine.platformChannel);
+  XCTAssertNil(engine.lifecycleChannel);
+
+  XCTAssertTrue([engine run]);
+
+  XCTAssertNotNil(engine.navigationChannel);
+  XCTAssertNotNil(engine.platformChannel);
+  XCTAssertNotNil(engine.lifecycleChannel);
+  XCTestExpectation* expectation =
+      [[XCTestExpectation alloc] initWithDescription:@"notification called"];
+  @autoreleasepool {
+    FlutterViewController* viewController = [[FlutterViewController alloc] initWithEngine:engine
+                                                                                  nibName:nil
+                                                                                   bundle:nil];
+    [engine setViewController:viewController];
+    [engine destroyContext];
+    [[NSNotificationCenter defaultCenter] addObserverForName:FlutterViewControllerWillDealloc
+                                                      object:nil
+                                                       queue:[NSOperationQueue mainQueue]
+                                                  usingBlock:^(NSNotification* _Nonnull note) {
+                                                    [expectation fulfill];
+                                                  }];
+    viewController = nil;
+  }
+  [self waitForExpectations:@[ expectation ] timeout:30.0];
+  XCTAssertNil(engine.navigationChannel);
+  XCTAssertNil(engine.platformChannel);
+  XCTAssertNil(engine.lifecycleChannel);
+}
+
 @end