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

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 +109,49 @@ - (CGRect)caretRectForPosition:(UITextPosition *)position
  return [super caretRectForPosition:position];
 }
 
+#pragma mark - Fix for CJK Languages
+
+/* 
+ * The workaround to fix inputting complex locales (like CJK languages).
+ * When we use `setAttrbutedText:` while user is inputting text in a complex
+ * locale (like Chinese, Japanese or Korean), some internal state breaks and
+ * input stops working.
+ *
+ * To workaround that, we don't skip underlying attributedString in the text
+ * field if only attributes were changed. We keep track of these attributes in
+ * a local variable.
+ *
+ * There are two methods that are altered by this workaround:
+ *
+ * (1) `-setAttributedText:` 
+ * Applies the attributed string change to a local variable `_attributesHolder` instead of calling `-[super setAttributedText:]`.
+ * If new attributed text differs from the existing one only in attributes,
+ * skips `-[super setAttributedText:`] completely.
+ *
+ * (2) `-attributedText` 
+ * Return `_attributesHolder` context.
+ * Updates `_atributesHolder` before returning if the underlying `super.attributedText.string` was changed.
+ *
+ */
+- (void)setAttributedText:(NSAttributedString *)attributedText
+{
+ BOOL textWasChanged = ![_attributesHolder.string isEqualToString:attributedText.string];
+ [_attributesHolder setAttributedString:attributedText];
+
+ if (textWasChanged) {
+ [super setAttributedText:attributedText];
+ }
+}
+
+- (NSAttributedString *)attributedText
+{
+ if (![super.attributedText.string isEqualToString:_attributesHolder.string]) {
+ [_attributesHolder setAttributedString:super.attributedText];
+ }
+
+ return _attributesHolder;
+}
+
 #pragma mark - Positioning Overrides
 
 - (CGRect)textRectForBounds:(CGRect)bounds