macOS fluttertextinputplugin drops selector called if no client (#52495)

The observed behavior is that if a keypress both reach framework and flutter textinputplugin selector and the keypress handler in framework causes the the textinputplugin to resign first responder, the selector will still go through even if the textinputplugin has already resigned.

The pr makes it so textinputplugin will ignore these selector call

fixes flutter/flutter#143270

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

Author: chunhtai

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

@@ -777,6 +777,10 @@ - (void)doCommandBySelector:(SEL)selector {
     void (*func)(id, SEL, id) = reinterpret_cast<void (*)(id, SEL, id)>(imp);
     func(self, selector, nil);
   }
+  if (self.clientID == nil) {
+    // The macOS may still call selector even if it is no longer a first responder.
+    return;
+  }
 
   if (selector == @selector(insertNewline:)) {
     // Already handled through text insertion (multiline) or action.

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

@@ -1801,6 +1801,42 @@ - (bool)testSelectorsAreForwardedToFramework {
   return true;
 }
 
+- (bool)testSelectorsNotForwardedToFrameworkIfNoClient {
+  id engineMock = flutter::testing::CreateMockFlutterEngine(@"");
+  id binaryMessengerMock = OCMProtocolMock(@protocol(FlutterBinaryMessenger));
+  OCMStub(  // NOLINT(google-objc-avoid-throwing-exception)
+      [engineMock binaryMessenger])
+      .andReturn(binaryMessengerMock);
+  // Make sure the selectors are not forwarded to the framework.
+  OCMReject([binaryMessengerMock sendOnChannel:@"flutter/textinput" message:[OCMArg any]]);
+  FlutterViewController* viewController = [[FlutterViewController alloc] initWithEngine:engineMock
+                                                                                nibName:@""
+                                                                                 bundle:nil];
+
+  FlutterTextInputPlugin* plugin =
+      [[FlutterTextInputPlugin alloc] initWithViewController:viewController];
+
+  // Can't run CFRunLoop in default mode because it causes crashes from scheduled
+  // sources from other tests.
+  NSString* runLoopMode = @"FlutterTestRunLoopMode";
+  plugin.customRunLoopMode = runLoopMode;
+
+  // Call selectors without setting a client.
+  [plugin doCommandBySelector:@selector(moveUp:)];
+  [plugin doCommandBySelector:@selector(moveRightAndModifySelection:)];
+
+  __block bool done = false;
+  CFRunLoopPerformBlock(CFRunLoopGetMain(), (__bridge CFStringRef)runLoopMode, ^{
+    done = true;
+  });
+
+  while (!done) {
+    CFRunLoopRunInMode((__bridge CFStringRef)runLoopMode, 0, true);
+  }
+  // At this point the selectors should be dropped; otherwise, OCMReject will throw.
+  return true;
+}
+
 @end
 
 namespace flutter::testing {
@@ -1886,7 +1922,7 @@ - (bool)testSelectorsAreForwardedToFramework {
   ASSERT_TRUE([[FlutterInputPluginTestObjc alloc] testComposingWithDelta]);
 }
 
-TEST(FlutterTextInputPluginTest, testComposingWithDeltasWhenSelectionIsActive) {
+TEST(FlutterTextInputPluginTest, TestComposingWithDeltasWhenSelectionIsActive) {
   ASSERT_TRUE([[FlutterInputPluginTestObjc alloc] testComposingWithDeltasWhenSelectionIsActive]);
 }
 
@@ -1910,6 +1946,10 @@ - (bool)testSelectorsAreForwardedToFramework {
   ASSERT_TRUE([[FlutterInputPluginTestObjc alloc] testSelectorsAreForwardedToFramework]);
 }
 
+TEST(FlutterTextInputPluginTest, TestSelectorsNotForwardedToFrameworkIfNoClient) {
+  ASSERT_TRUE([[FlutterInputPluginTestObjc alloc] testSelectorsNotForwardedToFrameworkIfNoClient]);
+}
+
 TEST(FlutterTextInputPluginTest, TestInsertNewLine) {
   ASSERT_TRUE([[FlutterInputPluginTestObjc alloc] testInsertNewLine]);
 }