Wait for binding to be ready before requesting exits from framework

Author: gspencergoog

shell/platform/darwin/macos/framework/Source/FlutterAppDelegate.mm

@@ -55,7 +55,7 @@ - (NSString*)applicationName {
 
 - (NSApplicationTerminateReply)applicationShouldTerminate:(NSApplication* _Nonnull)sender {
   // If the framework has already told us to terminate, terminate immediately.
-  if ([[self terminationHandler] shouldTerminate]) {
+  if ([self terminationHandler] == nil || [[self terminationHandler] shouldTerminate]) {
     return NSTerminateNow;
   }
 

shell/platform/darwin/macos/framework/Source/FlutterEngine.mm

@@ -170,6 +170,7 @@ @implementation FlutterEngineTerminationHandler {
 - (instancetype)initWithEngine:(FlutterEngine*)engine
                     terminator:(FlutterTerminationCallback)terminator {
   self = [super init];
+  _bindingIsReady = NO;
   _engine = engine;
   _terminator = terminator ? terminator : ^(id sender) {
     // Default to actually terminating the application. The terminator exists to
@@ -207,6 +208,11 @@ - (void)requestApplicationTermination:(id)sender
                              exitType:(FlutterAppExitType)type
                                result:(nullable FlutterResult)result {
   _shouldTerminate = YES;
+  if (![self bindingIsReady]) {
+    // Until the binding has signaled that it is ready to handle application
+    // termination requests, the app will just terminate when asked.
+    type = kFlutterAppExitTypeRequired;
+  }
   switch (type) {
     case kFlutterAppExitTypeCancelable: {
       FlutterJSONMethodCodec* codec = [FlutterJSONMethodCodec sharedInstance];
@@ -1031,6 +1037,8 @@ - (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
     result(@{@"value" : @([self clipboardHasStrings])});
   } else if ([call.method isEqualToString:@"System.exitApplication"]) {
     [[self terminationHandler] handleRequestAppExitMethodCall:call.arguments result:result];
+  } else if ([call.method isEqualToString:@"System.enableApplicationLifecycle"]) {
+    [self terminationHandler].bindingIsReady = YES;
   } else {
     result(FlutterMethodNotImplemented);
   }

shell/platform/darwin/macos/framework/Source/FlutterEngineTest.mm

@@ -742,6 +742,16 @@ - (nonnull NSView*)createWithViewIdentifier:(int64_t)viewId arguments:(nullable
       [FlutterMethodCall methodCallWithMethodName:@"System.exitApplication"
                                         arguments:@{@"type" : @"cancelable"}];
 
+  // Always terminate when the binding isn't ready (which is the default).
+  triedToTerminate = FALSE;
+  calledAfterTerminate = @"";
+  nextResponse = @"cancel";
+  [engineMock handleMethodCall:methodExitApplication result:appExitResult];
+  EXPECT_STREQ([calledAfterTerminate UTF8String], "");
+  EXPECT_TRUE(triedToTerminate);
+
+  // Once the binding is ready, handle the request.
+  terminationHandler.bindingIsReady = YES;
   triedToTerminate = FALSE;
   calledAfterTerminate = @"";
   nextResponse = @"exit";

shell/platform/darwin/macos/framework/Source/FlutterEngine_Internal.h

@@ -53,6 +53,7 @@ typedef NS_ENUM(NSInteger, FlutterAppExitResponse) {
 @interface FlutterEngineTerminationHandler : NSObject
 
 @property(nonatomic, readonly) BOOL shouldTerminate;
+@property(nonatomic, readwrite) BOOL bindingIsReady;
 
 - (instancetype)initWithEngine:(FlutterEngine*)engine
                     terminator:(nullable FlutterTerminationCallback)terminator;