[macos] FlutterKeyboardManager memory leak fix

Break cycle references, due to implicitely captured 'this'

Author: sergiy-sc

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

@@ -123,18 +123,24 @@ - (nonnull instancetype)initWithViewDelegate:(nonnull id<FlutterKeyboardViewDele
         [FlutterMethodChannel methodChannelWithName:@"flutter/keyboard"
                                     binaryMessenger:[_viewDelegate getBinaryMessenger]
                                               codec:[FlutterStandardMethodCodec sharedInstance]];
+
     [keyboardChannel setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
       [self handleKeyboardMethodCall:call result:result];
     }];
+
     _primaryResponders = [[NSMutableArray alloc] init];
+
+    __weak __typeof__(self) weakSelf = self;
     [self addPrimaryResponder:[[FlutterEmbedderKeyResponder alloc]
                                   initWithSendEvent:^(const FlutterKeyEvent& event,
                                                       FlutterKeyEventCallback callback,
                                                       void* userData) {
-                                    [_viewDelegate sendKeyEvent:event
-                                                       callback:callback
-                                                       userData:userData];
+                                    __strong __typeof__(weakSelf) strongSelf = weakSelf;
+                                    [strongSelf.viewDelegate sendKeyEvent:event
+                                                                 callback:callback
+                                                                 userData:userData];
                                   }]];
+
     [self
         addPrimaryResponder:[[FlutterChannelKeyResponder alloc]
                                 initWithChannel:[FlutterBasicMessageChannel
@@ -143,14 +149,14 @@ - (nonnull instancetype)initWithViewDelegate:(nonnull id<FlutterKeyboardViewDele
                                                                                getBinaryMessenger]
                                                                      codec:[FlutterJSONMessageCodec
                                                                                sharedInstance]]]];
+
     _pendingEvents = [[NSMutableArray alloc] init];
     _layoutMap = [NSMutableDictionary<NSNumber*, NSNumber*> dictionary];
     [self buildLayout];
     for (id<FlutterKeyPrimaryResponder> responder in _primaryResponders) {
       responder.layoutMap = _layoutMap;
     }
 
-    __weak __typeof__(self) weakSelf = self;
     [_viewDelegate subscribeToKeyboardLayoutChange:^() {
       [weakSelf buildLayout];
     }];

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

@@ -426,9 +426,11 @@ - (bool)getPressedState;
 - (bool)keyboardChannelGetPressedState;
 - (bool)racingConditionBetweenKeyAndText;
 - (bool)correctLogicalKeyForLayouts;
+- (bool)shouldNotHoldStrongReferenceToViewDelegate;
 @end
 
 namespace flutter::testing {
+
 TEST(FlutterKeyboardManagerUnittests, SinglePrimaryResponder) {
   ASSERT_TRUE([[FlutterKeyboardManagerUnittestsObjC alloc] singlePrimaryResponder]);
 }
@@ -461,6 +463,11 @@ - (bool)correctLogicalKeyForLayouts;
   ASSERT_TRUE([[FlutterKeyboardManagerUnittestsObjC alloc] correctLogicalKeyForLayouts]);
 }
 
+TEST(FlutterKeyboardManagerUnittests, ShouldNotHoldStrongReferenceToViewDelegate) {
+  ASSERT_TRUE(
+      [[FlutterKeyboardManagerUnittestsObjC alloc] shouldNotHoldStrongReferenceToViewDelegate]);
+}
+
 }  // namespace flutter::testing
 
 @implementation FlutterKeyboardManagerUnittestsObjC
@@ -809,4 +816,30 @@ - (bool)correctLogicalKeyForLayouts {
   return TRUE;
 }
 
+- (bool)shouldNotHoldStrongReferenceToViewDelegate {
+  __strong FlutterKeyboardManager* strongKeyboardManager;
+  __weak id weakViewDelegate;
+
+  @autoreleasepool {
+    id binaryMessengerMock = OCMStrictProtocolMock(@protocol(FlutterBinaryMessenger));
+    OCMStub([binaryMessengerMock setMessageHandlerOnChannel:[OCMArg any]
+                                       binaryMessageHandler:[OCMArg any]]);
+
+    id viewDelegateMock = OCMStrictProtocolMock(@protocol(FlutterKeyboardViewDelegate));
+    OCMStub([viewDelegateMock getBinaryMessenger]).andReturn(binaryMessengerMock);
+    OCMStub([viewDelegateMock subscribeToKeyboardLayoutChange:[OCMArg any]]);
+
+    LayoutClue layoutClue;
+    OCMStub([viewDelegateMock lookUpLayoutForKeyCode:0 shift:NO])
+        .ignoringNonObjectArgs()
+        .andReturn(layoutClue);
+    FlutterKeyboardManager* keyboardManager =
+        [[FlutterKeyboardManager alloc] initWithViewDelegate:viewDelegateMock];
+    strongKeyboardManager = keyboardManager;
+    weakViewDelegate = viewDelegateMock;
+  }
+
+  return weakViewDelegate == nil;
+}
+
 @end