fixes reference retaining issue in flutter text input plugin (#24768)

Author: chunhtai

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

@@ -1236,7 +1236,7 @@ @interface FlutterTextInputPlugin ()
 // The current password-autofillable input fields that have yet to be saved.
 @property(nonatomic, readonly)
     NSMutableDictionary<NSString*, FlutterTextInputView*>* autofillContext;
-@property(nonatomic, assign) FlutterTextInputView* activeView;
+@property(nonatomic, strong) FlutterTextInputView* activeView;
 @property(nonatomic, strong) FlutterTextInputViewAccessibilityHider* inputHider;
 @end
 
@@ -1253,7 +1253,7 @@ - (instancetype)init {
     _reusableInputView = [[FlutterTextInputView alloc] init];
     _reusableInputView.secureTextEntry = NO;
     _autofillContext = [[NSMutableDictionary alloc] init];
-    _activeView = _reusableInputView;
+    _activeView = [_reusableInputView retain];
     _inputHider = [[FlutterTextInputViewAccessibilityHider alloc] init];
   }
 
@@ -1263,6 +1263,7 @@ - (instancetype)init {
 - (void)dealloc {
   [self hideTextInput];
   [_reusableInputView release];
+  [_activeView release];
   [_inputHider release];
   [_autofillContext release];
   [super dealloc];
@@ -1386,19 +1387,19 @@ - (void)setTextInputClient:(int)client withConfiguration:(NSDictionary*)configur
   [self changeInputViewsAutofillVisibility:NO];
   switch (autofillTypeOf(configuration)) {
     case FlutterAutofillTypeNone:
-      _activeView = [self updateAndShowReusableInputView:configuration];
+      self.activeView = [self updateAndShowReusableInputView:configuration];
       break;
     case FlutterAutofillTypeRegular:
       // If the group does not involve password autofill, only install the
       // input view that's being focused.
-      _activeView = [self updateAndShowAutofillViews:nil
-                                        focusedField:configuration
-                                   isPasswordRelated:NO];
+      self.activeView = [self updateAndShowAutofillViews:nil
+                                            focusedField:configuration
+                                       isPasswordRelated:NO];
       break;
     case FlutterAutofillTypePassword:
-      _activeView = [self updateAndShowAutofillViews:configuration[kAssociatedAutofillFields]
-                                        focusedField:configuration
-                                   isPasswordRelated:YES];
+      self.activeView = [self updateAndShowAutofillViews:configuration[kAssociatedAutofillFields]
+                                            focusedField:configuration
+                                       isPasswordRelated:YES];
       break;
   }
 

shell/platform/darwin/ios/framework/Source/FlutterTextInputPluginTest.m

@@ -865,4 +865,31 @@ - (void)testFlutterTokenizerCanParseLines {
   XCTAssertEqual(range.range.length, 20u);
 }
 
+- (void)testFlutterTextInputPluginRetainsFlutterTextInputView {
+  FlutterTextInputPlugin* myInputPlugin;
+  id myEngine = OCMClassMock([FlutterEngine class]);
+  myInputPlugin = [[FlutterTextInputPlugin alloc] init];
+  myInputPlugin.textInputDelegate = myEngine;
+  __weak UIView* activeView;
+  @autoreleasepool {
+    FlutterMethodCall* setClientCall = [FlutterMethodCall
+        methodCallWithMethodName:@"TextInput.setClient"
+                       arguments:@[
+                         [NSNumber numberWithInt:123], self.mutablePasswordTemplateCopy
+                       ]];
+    [myInputPlugin handleMethodCall:setClientCall
+                             result:^(id _Nullable result){
+                             }];
+    activeView = myInputPlugin.textInputView;
+    FlutterMethodCall* hideCall = [FlutterMethodCall methodCallWithMethodName:@"TextInput.hide"
+                                                                    arguments:@[]];
+    [myInputPlugin handleMethodCall:hideCall
+                             result:^(id _Nullable result){
+                             }];
+    XCTAssertNotNil(activeView);
+  }
+  // This assert proves the myInputPlugin.textInputView is not deallocated.
+  XCTAssertNotNil(activeView);
+}
+
 @end