fix(macos): TextInput Fabric commands - setGhostText, blur, and selection fixes (#2912)

## Summary

TextInput commands (`setGhostText`, `blur`, `setSelection`) don't work
correctly under Fabric on macOS. This PR fixes three issues:

- **Add missing `setGhostText` command to Fabric**: Ghost text was
implemented for Paper in #1890 / #1897 (with undo fixes in #2105 /
#2106), but the Fabric command dispatcher and component view never got
the implementation. This ports the ghost text logic (insertion, removal,
attributes, delegate cleanup) from `RCTBaseTextInputView` to
`RCTTextInputComponentView`.
- **Fix `blur` command on macOS Fabric**: `blur` was a silent no-op
because it compared `[window firstResponder]` against the NSTextField,
but on macOS the firstResponder during editing is the field editor
(NSTextView), not the text field itself. Fixed by checking
`currentEditor` on NSTextField.
- **Fix ghost text being selectable on Fabric**: Ghost text could be
selected by the user on Fabric (but not Paper). Added cleanup in
`textInputDidChangeSelection` to clear ghost text when the user changes
selection, matching Paper behavior.
- **Fix `setTextAndSelection` delegate notification**: Changed
`notifyDelegate:YES` to `notifyDelegate:NO` to match Paper's
`setSelectionStart:selectionEnd:` behavior and prevent spurious delegate
callbacks during programmatic selection changes.

## Test plan

- [x] Verified `setGhostText` command works via RNTester on macOS Fabric
- [x] Verified `blur` command works on macOS Fabric  
- [x] Verified ghost text is not selectable on Fabric
- [x] Verified `focus`, `clear`, `setSelection` commands still work
- [x] JS TextInput tests pass

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: Saadnajmi

packages/react-native/Libraries/Components/TextInput/__tests__/TextInput-test.js

@@ -65,6 +65,10 @@ jest.unmock('../TextInput');
 
       expect(inputElement.isFocused).toBeInstanceOf(Function); // Would have prevented S168585
       expect(inputElement.clear).toBeInstanceOf(Function);
+      // [macOS
+      expect(inputElement.setSelection).toBeInstanceOf(Function);
+      expect(inputElement.setGhostText).toBeInstanceOf(Function);
+      // macOS]
       // $FlowFixMe[method-unbinding]
       expect(inputElement.focus).toBeInstanceOf(jest.fn().constructor);
       // $FlowFixMe[method-unbinding]

packages/react-native/Libraries/Text/TextInput/Multiline/RCTUITextView.mm

@@ -328,10 +328,19 @@ - (void)setAttributedText:(NSAttributedString *)attributedText
 #if !TARGET_OS_OSX // [macOS]
   [super setAttributedText:attributedText];
 #else // [macOS
-  // Break undo coalescing when the text is changed by JS (e.g. autocomplete).
-  [self breakUndoCoalescing];
-  // Avoid Exception thrown while executing UI block: *** -[NSBigMutableString replaceCharactersInRange:withString:]: nil argument
-  [self.textStorage setAttributedString:attributedText ?: [NSAttributedString new]];
+  if (self.ghostTextChanging) {
+    // Ghost text changes should not be on the undo stack. Disable undo
+    // registration around the text storage mutation so Cmd+Z skips over
+    // ghost text insertions/removals.
+    [self.undoManager disableUndoRegistration];
+    [self.textStorage setAttributedString:attributedText ?: [NSAttributedString new]];
+    [self.undoManager enableUndoRegistration];
+  } else {
+    // Break undo coalescing when the text is changed by JS (e.g. autocomplete).
+    [self breakUndoCoalescing];
+    // Avoid Exception thrown while executing UI block: *** -[NSBigMutableString replaceCharactersInRange:withString:]: nil argument
+    [self.textStorage setAttributedString:attributedText ?: [NSAttributedString new]];
+  }
 #endif // macOS]
   [self textDidChange];
 }

packages/react-native/React/Fabric/Mounting/ComponentViews/TextInput/RCTTextInputComponentView.mm

@@ -102,6 +102,10 @@ @implementation RCTTextInputComponentView {
 
   BOOL _hasInputAccessoryView;
   CGSize _previousContentSize;
+#if TARGET_OS_OSX // [macOS
+  NSString *_ghostText;
+  NSInteger _ghostTextPosition;
+#endif // macOS]
 }
 
 #pragma mark - UIView overrides
@@ -513,6 +517,10 @@ - (void)prepareForRecycle
   _lastStringStateWasUpdatedWith = nil;
   _ignoreNextTextInputCall = NO;
   _didMoveToWindow = NO;
+#if TARGET_OS_OSX // [macOS
+  _ghostText = nil;
+  _ghostTextPosition = 0;
+#endif // macOS]
   [_backedTextInputView resignFirstResponder];
 }
 
@@ -537,6 +545,10 @@ - (BOOL)textInputShouldEndEditing
 
 - (void)textInputDidEndEditing
 {
+#if TARGET_OS_OSX // [macOS
+  [self setGhostText:nil];
+#endif // macOS]
+
   if (_eventEmitter) {
     static_cast<const TextInputEventEmitter &>(*_eventEmitter).onEndEditing([self _textInputMetrics]);
     static_cast<const TextInputEventEmitter &>(*_eventEmitter).onBlur([self _textInputMetrics]);
@@ -571,6 +583,12 @@ - (void)textInputDidReturn
 
 - (NSString *)textInputShouldChangeText:(NSString *)text inRange:(NSRange)range
 {
+#if TARGET_OS_OSX // [macOS
+  // Clear ghost text before the text change so the undo manager's snapshot
+  // of the pre-edit state never contains ghost text.
+  [self setGhostText:nil];
+#endif // macOS]
+
   const auto &props = static_cast<const TextInputProps &>(*_props);
 
   if (!_backedTextInputView.textWasPasted) {
@@ -616,6 +634,17 @@ - (void)textInputDidChange
     return;
   }
 
+#if TARGET_OS_OSX // [macOS
+  if (_ghostText != nil) {
+    NSAttributedString *attributedStringWithoutGhostText = [self removingGhostTextFromString:_backedTextInputView.attributedText strict:NO];
+    if (attributedStringWithoutGhostText != nil && ![attributedStringWithoutGhostText isEqual:_backedTextInputView.attributedText]) {
+      _backedTextInputView.attributedText = attributedStringWithoutGhostText;
+    }
+    _ghostText = nil;
+    _ghostTextPosition = 0;
+  }
+#endif // macOS]
+
   if (_ignoreNextTextInputCall && [_lastStringStateWasUpdatedWith isEqual:_backedTextInputView.attributedText]) {
     _ignoreNextTextInputCall = NO;
     return;
@@ -631,6 +660,14 @@ - (void)textInputDidChange
 
 - (void)textInputDidChangeSelection
 {
+#if TARGET_OS_OSX // [macOS
+  // Clear ghost text on any user selection change, matching Paper behavior.
+  // This prevents the user from selecting ghost text.
+  if (_ghostText != nil && !_comingFromJS && !_backedTextInputView.ghostTextChanging) {
+    [self setGhostText:nil];
+  }
+#endif // macOS]
+
   if (_comingFromJS) {
     return;
   }
@@ -804,6 +841,115 @@ - (void)scrollViewDidScroll:(RCTUIScrollView *)scrollView // [macOS]
   }
 }
 
+#if TARGET_OS_OSX // [macOS
+#pragma mark - Ghost Text
+
+- (NSDictionary<NSAttributedStringKey, id> *)ghostTextAttributes
+{
+  NSMutableDictionary<NSAttributedStringKey, id> *textAttributes =
+      [_backedTextInputView.defaultTextAttributes mutableCopy] ?: [NSMutableDictionary new];
+
+  [textAttributes setValue:_backedTextInputView.placeholderColor ?: [RCTPlatformColor placeholderTextColor]
+                    forKey:NSForegroundColorAttributeName];
+
+  return textAttributes;
+}
+
+- (void)setGhostText:(NSString *)ghostText
+{
+  NSRange selectedRange = [_backedTextInputView selectedTextRange];
+  NSInteger selectionStart = selectedRange.location;
+  NSInteger selectionEnd = selectedRange.location + selectedRange.length;
+  NSString *newGhostText = ghostText.length > 0 ? ghostText : nil;
+
+  if (selectionStart != selectionEnd) {
+    newGhostText = nil;
+  }
+
+  if ((_ghostText == nil && newGhostText == nil) || [_ghostText isEqual:newGhostText]) {
+    return;
+  }
+
+  if (_backedTextInputView.ghostTextChanging) {
+    // look out for nested callbacks -- this can happen for example when selection changes in response to
+    // attributed text changing. Such callbacks are initiated by Apple, or we could suppress this other ways.
+    return;
+  }
+
+  _backedTextInputView.ghostTextChanging = YES;
+
+  if (_ghostText != nil) {
+    // When setGhostText: is called after making a standard edit, the ghost text may already be gone
+    BOOL ghostTextMayAlreadyBeGone = newGhostText == nil;
+    NSAttributedString *attributedStringWithoutGhostText = [self removingGhostTextFromString:_backedTextInputView.attributedText strict:!ghostTextMayAlreadyBeGone];
+
+    if (attributedStringWithoutGhostText != nil) {
+      _backedTextInputView.attributedText = attributedStringWithoutGhostText;
+      [_backedTextInputView setSelectedTextRange:NSMakeRange(selectionStart, selectionEnd - selectionStart) notifyDelegate:NO];
+    }
+  }
+
+  _ghostText = [newGhostText copy];
+  _ghostTextPosition = selectionStart;
+
+  if (_ghostText != nil) {
+    NSMutableAttributedString *attributedString = [_backedTextInputView.attributedText mutableCopy];
+    NSAttributedString *ghostAttributedString = [[NSAttributedString alloc] initWithString:_ghostText
+                                                                                attributes:self.ghostTextAttributes];
+
+    [attributedString insertAttributedString:ghostAttributedString atIndex:_ghostTextPosition];
+    _backedTextInputView.attributedText = attributedString;
+    [_backedTextInputView setSelectedTextRange:NSMakeRange(_ghostTextPosition, 0) notifyDelegate:NO];
+  }
+
+  _backedTextInputView.ghostTextChanging = NO;
+}
+
+/**
+ * Attempts to remove the ghost text from a provided string given our current state.
+ *
+ * If `strict` mode is enabled, this method assumes the ghost text exists exactly
+ * where we expect it to be. We assert and return `nil` if we don't find the expected ghost text.
+ * It's the responsibility of the caller to make sure the result isn't `nil`.
+ *
+ * If disabled, we allow for the possibility that the ghost text has already been removed,
+ * which can happen if a delegate callback is trying to remove ghost text after invoking `setAttributedText:`.
+ */
+- (NSAttributedString *)removingGhostTextFromString:(NSAttributedString *)string strict:(BOOL)strict
+{
+  if (_ghostText == nil) {
+    return string;
+  }
+
+  NSRange ghostTextRange = NSMakeRange(_ghostTextPosition, _ghostText.length);
+  NSMutableAttributedString *attributedString = [string mutableCopy];
+
+  if ([attributedString length] < NSMaxRange(ghostTextRange)) {
+    if (strict) {
+      RCTAssert(false, @"Ghost text not fully present in text view text");
+      return nil;
+    } else {
+      return string;
+    }
+  }
+
+  NSString *actualGhostText = [[attributedString attributedSubstringFromRange:ghostTextRange] string];
+
+  if (![actualGhostText isEqual:_ghostText]) {
+    if (strict) {
+      RCTAssert(false, @"Ghost text does not match text view text");
+      return nil;
+    } else {
+      return string;
+    }
+  }
+
+  [attributedString deleteCharactersInRange:ghostTextRange];
+  return attributedString;
+}
+
+#endif // macOS]
+
 #pragma mark - Native Commands
 
 - (void)handleCommand:(const NSString *)commandName args:(const NSArray *)args
@@ -841,7 +987,13 @@ - (void)blur
   [_backedTextInputView resignFirstResponder];
 #else // [macOS
   NSWindow *window = [_backedTextInputView window];
-  if ([window firstResponder] == _backedTextInputView.responder) {
+  // On macOS, when an NSTextField is focused, the window's firstResponder is the
+  // field editor (an NSTextView), not the text field itself. Check currentEditor
+  // to determine if the text field is actively being edited.
+  if ([_backedTextInputView isKindOfClass:[NSTextField class]] &&
+      [(NSTextField *)_backedTextInputView currentEditor] != nil) {
+    [window makeFirstResponder:nil];
+  } else if ([window firstResponder] == _backedTextInputView.responder) {
     [window makeFirstResponder:nil];
   }
 #endif // macOS]
@@ -880,7 +1032,7 @@ - (void)setTextAndSelection:(NSInteger)eventCount
 #else // [macOS
   NSInteger startPosition = MIN(start, end);
   NSInteger endPosition = MAX(start, end);
-  [_backedTextInputView setSelectedTextRange:NSMakeRange(startPosition, endPosition - startPosition) notifyDelegate:YES];
+  [_backedTextInputView setSelectedTextRange:NSMakeRange(startPosition, endPosition - startPosition) notifyDelegate:NO];
 #endif // macOS]
   _comingFromJS = NO;
 }

packages/react-native/React/Fabric/Mounting/ComponentViews/TextInput/RCTTextInputNativeCommands.h

@@ -18,6 +18,9 @@ NS_ASSUME_NONNULL_BEGIN
                       value:(NSString *__nullable)value
                       start:(NSInteger)start
                         end:(NSInteger)end;
+#if TARGET_OS_OSX // [macOS
+- (void)setGhostText:(NSString *__nullable)ghostText;
+#endif // macOS]
 @end
 
 RCT_EXTERN inline void
@@ -96,6 +99,23 @@ RCTTextInputHandleCommand(id<RCTTextInputViewProtocol> componentView, const NSSt
     return;
   }
 
+#if TARGET_OS_OSX // [macOS
+  if ([commandName isEqualToString:@"setGhostText"]) {
+#if RCT_DEBUG
+    if ([args count] != 1) {
+      RCTLogError(
+          @"%@ command %@ received %d arguments, expected %d.", @"TextInput", commandName, (int)[args count], 1);
+      return;
+    }
+#endif
+
+    NSObject *arg0 = args[0];
+    NSString *value = [arg0 isKindOfClass:[NSNull class]] ? nil : (NSString *)arg0;
+    [componentView setGhostText:value];
+    return;
+  }
+#endif // macOS]
+
 #if RCT_DEBUG
   RCTLogError(@"%@ received command %@, which is not a supported command.", @"TextInput", commandName);
 #endif