[iOS TextInputPlugin] fix autofill assert (flutter/engine#26711)

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterTextInputPlugin.mm

@@ -1371,8 +1371,11 @@ static FlutterAutofillType autofillTypeOf(NSDictionary* configuration) {
     _autofillContext = [[NSMutableDictionary alloc] init];
     _inputHider = [[FlutterTextInputViewAccessibilityHider alloc] init];
     // Initialize activeView with a dummy view to keep tests
-    // passing.
+    // passing. This dummy view needs to be replace once the
+    // framework initializes an input connection, and thus
+    // should never have access to the textInputDelegate.
     _activeView = [[FlutterTextInputView alloc] init];
+    [_activeView decommission];
   }
 
   return self;
@@ -1383,6 +1386,9 @@ static FlutterAutofillType autofillTypeOf(NSDictionary* configuration) {
   _activeView.textInputDelegate = nil;
   [_activeView release];
   [_inputHider release];
+  for (FlutterTextInputView* autofillView in _autofillContext.allValues) {
+    autofillView.textInputDelegate = nil;
+  }
   [_autofillContext release];
   [super dealloc];
 }
@@ -1477,13 +1483,12 @@ static FlutterAutofillType autofillTypeOf(NSDictionary* configuration) {
   [self removeEnableFlutterTextInputViewAccessibilityTimer];
   _activeView.accessibilityEnabled = NO;
   [_activeView resignFirstResponder];
-  [_activeView decommission];
   [_activeView removeFromSuperview];
   [_inputHider removeFromSuperview];
 }
 
 - (void)triggerAutofillSave:(BOOL)saveEntries {
-  [self hideTextInput];
+  [_activeView resignFirstResponder];
 
   if (saveEntries) {
     // Make all the input fields in the autofill context visible,

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterTextInputPluginTest.m

@@ -80,6 +80,9 @@ FLUTTER_ASSERT_ARC
 }
 
 - (void)tearDown {
+  for (FlutterTextInputView* autofillView in textInputPlugin.autofillContext.allValues) {
+    autofillView.textInputDelegate = nil;
+  }
   [textInputPlugin.autofillContext removeAllObjects];
   [textInputPlugin cleanUpViewHierarchy:YES clearText:YES delayRemoval:NO];
   [[[[textInputPlugin textInputView] superview] subviews]
@@ -896,6 +899,38 @@ FLUTTER_ASSERT_ARC
   [self commitAutofillContextAndVerify];
 }
 
+- (void)testDecommissionedViewAreNotReusedByAutofill {
+  // Regression test for https://github.com/flutter/flutter/issues/84407.
+  NSMutableDictionary* configuration = self.mutableTemplateCopy;
+  [configuration setValue:@{
+    @"uniqueIdentifier" : @"field1",
+    @"hints" : @[ UITextContentTypePassword ],
+    @"editingValue" : @{@"text" : @""}
+  }
+                   forKey:@"autofill"];
+  [configuration setValue:@[ [configuration copy] ] forKey:@"fields"];
+
+  [self setClientId:123 configuration:configuration];
+
+  [self setTextInputHide];
+  UIView* previousActiveView = textInputPlugin.activeView;
+
+  [self setClientId:124 configuration:configuration];
+
+  // Make sure the autofillable view is reused.
+  XCTAssertEqual(previousActiveView, textInputPlugin.activeView);
+  XCTAssertNotNil(previousActiveView);
+  // Does not crash.
+}
+
+- (void)testInitialActiveViewCantAccessTextInputDelegate {
+  textInputPlugin.activeView.textInputDelegate = engine;
+  // Before the framework sends the first text input configuration,
+  // the dummy "activeView" we use should never have access to
+  // its textInputDelegate.
+  XCTAssertNil(textInputPlugin.activeView.textInputDelegate);
+}
+
 #pragma mark - Accessibility - Tests
 
 - (void)testUITextInputAccessibilityNotHiddenWhenShowed {