[iOS][TextInput] Apply the fix for CJK languages on single-line text fields.

Author: mandrigin

Libraries/Text/TextInput/Multiline/RCTUITextView.m

@@ -110,24 +110,25 @@ - (void)setTextAlignment:(NSTextAlignment)textAlignment
 
 - (void)setAttributedText:(NSAttributedString *)attributedText
 {
-  // Using `setAttributedString:` while user is typing breaks some internal mechanics
-  // when entering complex input languages such as Chinese, Korean or Japanese.
-  // see: https://github.com/facebook/react-native/issues/19339
-
-  // We try to avoid calling this method as much as we can.
-  // If the text has changed, there is nothing we can do.
-  if (![super.attributedText.string isEqualToString:attributedText.string]) {
-    [super setAttributedText:attributedText];
-  } else {
-  // But if the text is preserved, we just copying the attributes from the source string.
-    if (![super.attributedText isEqualToAttributedString:attributedText]) {
-      [self copyTextAttributesFrom:attributedText];
-    }
-  }
-
+  [super setAttributedText:attributedText];
   [self textDidChange];
 }
 
+#pragma mark - Fix for CJK languages
+// Search for `GH-19339` to see all code affected by this fix.
+
+- (void)copyAttributesFrom:(NSAttributedString *)sourceString
+{
+  [self.textStorage beginEditing];
+  NSTextStorage *textStorage = self.textStorage;
+  [sourceString enumerateAttributesInRange:NSMakeRange(0, sourceString.length)
+                                   options:NSAttributedStringEnumerationReverse
+                                usingBlock:^(NSDictionary<NSAttributedStringKey,id> * _Nonnull attrs, NSRange range, BOOL * _Nonnull stop) {
+                                  [textStorage setAttributes:attrs range:range];
+                                }];
+  [self.textStorage endEditing];
+}
+
 #pragma mark - Overrides
 
 - (void)setSelectedTextRange:(UITextRange *)selectedTextRange notifyDelegate:(BOOL)notifyDelegate
@@ -255,20 +256,4 @@ - (void)invalidatePlaceholderVisibility
   _placeholderView.hidden = !isVisible;
 }
 
-#pragma mark - Utility Methods
-
-- (void)copyTextAttributesFrom:(NSAttributedString *)sourceString
-{
-  [self.textStorage beginEditing];
-
-  NSTextStorage *textStorage = self.textStorage;
-  [sourceString enumerateAttributesInRange:NSMakeRange(0, sourceString.length)
-                                   options:NSAttributedStringEnumerationReverse
-                                usingBlock:^(NSDictionary<NSAttributedStringKey,id> * _Nonnull attrs, NSRange range, BOOL * _Nonnull stop) {
-                                  [textStorage setAttributes:attrs range:range];
-                                }];
-
-  [self.textStorage endEditing];
-}
-
 @end

Libraries/Text/TextInput/RCTBackedTextInputViewProtocol.h

@@ -38,6 +38,13 @@ NS_ASSUME_NONNULL_BEGIN
 // Use `attributedText.string` instead.
 @property (nonatomic, copy, nullable) NSString *text NS_UNAVAILABLE;
 
+// This operation copies only the attributes from `attributedText`.
+// It should be implemented in a way that doesn't break internal state of the text view.
+// See more at: https://github.com/facebook/react-native/issues/19339
+//
+// Search for `GH-19339` to see all code affected by this fix.
+- (void)copyAttributesFrom:(NSAttributedString *)attributedText;
+
 @end
 
 NS_ASSUME_NONNULL_END

Libraries/Text/TextInput/RCTBaseTextInputView.m

@@ -138,7 +138,7 @@ - (void)setAttributedText:(NSAttributedString *)attributedText
     UITextRange *selection = self.backedTextInputView.selectedTextRange;
     NSInteger oldTextLength = self.backedTextInputView.attributedText.string.length;
 
-    self.backedTextInputView.attributedText = attributedText;
+    [self safeSetAttributedText:attributedText];
 
     if (selection.empty) {
       // Maintaining a cursor position relative to the end of the old text.
@@ -160,6 +160,28 @@ - (void)setAttributedText:(NSAttributedString *)attributedText
   }
 }
 
+- (void)safeSetAttributedText:(NSAttributedString *)attributedText {
+  /*
+   // Search for `GH-19339` to see all code affected by this fix.
+   //
+   // Using `setAttributedString:` while user is typing breaks text field's external state
+   // when entering complex input languages such as Chinese, Korean or Japanese.
+   // see: https://github.com/facebook/react-native/issues/19339
+   // We try to avoid calling this method as much as we can.
+   //
+   // If the text has changed, there is nothing we can do.
+   */
+   if (![self.backedTextInputView.attributedText.string isEqualToString:attributedText.string]) {
+     self.backedTextInputView.attributedText = attributedText;
+   } else {
+     // But if the text is preserved, we just copying the attributes from the source string.
+     // This operation doesn't reset textView's internal state.
+     if (![self.backedTextInputView.attributedText isEqualToAttributedString:attributedText]) {
+       [self.backedTextInputView copyAttributesFrom:attributedText];
+     }
+   }
+}
+
 - (RCTTextSelection *)selection
 {
   id<RCTBackedTextInputViewProtocol> backedTextInputView = self.backedTextInputView;

Libraries/Text/TextInput/Singleline/RCTUITextField.m

@@ -14,6 +14,7 @@
 
 @implementation RCTUITextField {
   RCTBackedTextFieldDelegateAdapter *_textInputDelegateAdapter;
+  NSMutableAttributedString *_attributesHolder;
 }
 
 - (instancetype)initWithFrame:(CGRect)frame
@@ -25,6 +26,7 @@ - (instancetype)initWithFrame:(CGRect)frame
                                                object:self];
 
     _textInputDelegateAdapter = [[RCTBackedTextFieldDelegateAdapter alloc] initWithTextField:self];
+    _attributesHolder = [[NSMutableAttributedString alloc] init];
   }
 
   return self;
@@ -107,6 +109,29 @@ - (CGRect)caretRectForPosition:(UITextPosition *)position
   return [super caretRectForPosition:position];
 }
 
+#pragma mark - Fix for CJK Languages
+// Search for `GH-19339` to see all code affected by this fix.
+
+- (void)setAttributedText:(NSAttributedString *)attributedText {
+  [_attributesHolder setAttributedString:attributedText];
+  [super setAttributedText:attributedText];
+}
+
+- (void)copyAttributesFrom:(NSAttributedString *)source {
+  [_attributesHolder setAttributedString:super.attributedText];
+}
+
+- (NSAttributedString *)attributedText {
+  // For the text contents `super.attributedText.string` is the source of truth.
+  // If it differs, we match our internal state to it.
+  if(![super.attributedText.string isEqualToString:_attributesHolder.string]) {
+    [_attributesHolder setAttributedString:super.attributedText];
+  }
+
+  // For the text attributes, our internal state is the source of truth.
+  return _attributesHolder;
+}
+
 #pragma mark - Positioning Overrides
 
 - (CGRect)textRectForBounds:(CGRect)bounds