Fix a broken input for the Korean alphabet in TextInput (#32523)

Summary:
<!-- Explain the **motivation** for making this change. What existing problem does the pull request solve? -->

Fix #32503

Updating the attributed text in TextView/TextField while inputting Korean language will break input mechanism of the Korean alphabet. This results unexpected text input.

This PR supersedes the previous fixes: #19809, #22546

## Changelog

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https://github.com/facebook/react-native/wiki/Changelog
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[iOS] [Fixed] - Fix a broken input for the Korean alphabet in TextInput

Pull Request resolved: #32523

Test Plan: https://user-images.githubusercontent.com/20317121/140013434-1674c391-54d6-4410-b4c1-c633697e639d.mov

Reviewed By: lunaleaps, sammy-SC

Differential Revision: D32470543

Pulled By: philIip

fbshipit-source-id: e7e34bd362fa2ab2ca579103db01ad8d1a891c35

Libraries/Text/TextInput/Multiline/RCTUITextView.m

@@ -147,21 +147,7 @@ - (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];
 }
 
@@ -311,18 +297,4 @@ - (CGRect)caretRectForPosition:(UITextPosition *)position
 
 #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/RCTBaseTextInputView.m

@@ -104,6 +104,7 @@ - (BOOL)textOf:(NSAttributedString*)newText equals:(NSAttributedString*)oldText{
   // Similarly, when the user is in the middle of inputting some text in Japanese/Chinese, there will be styling on the
   // text that we should disregard. See https://developer.apple.com/documentation/uikit/uitextinput/1614489-markedtextrange?language=objc
   // for more info.
+  // Also, updating the attributed text while inputting Korean language will break input mechanism.
   // If the user added an emoji, the system adds a font attribute for the emoji and stores the original font in NSOriginalFont.
   // Lastly, when entering a password, etc., there will be additional styling on the field as the native text view
   // handles showing the last character for a split second.
@@ -116,6 +117,7 @@ - (BOOL)textOf:(NSAttributedString*)newText equals:(NSAttributedString*)oldText{
 
   BOOL shouldFallbackToBareTextComparison =
     [self.backedTextInputView.textInputMode.primaryLanguage isEqualToString:@"dictation"] ||
+    [self.backedTextInputView.textInputMode.primaryLanguage isEqualToString:@"ko-KR"] ||
     self.backedTextInputView.markedTextRange ||
     self.backedTextInputView.isSecureTextEntry ||
     fontHasBeenUpdatedBySystem;

React/Fabric/Mounting/ComponentViews/TextInput/RCTTextInputComponentView.mm

@@ -617,8 +617,9 @@ - (BOOL)_textOf:(NSAttributedString *)newText equals:(NSAttributedString *)oldTe
   // the settings on a dictation.
   // Similarly, when the user is in the middle of inputting some text in Japanese/Chinese, there will be styling on the
   // text that we should disregard. See
-  // https://developer.apple.com/documentation/uikit/uitextinput/1614489-markedtextrange?language=objc for more info. If
-  // the user added an emoji, the system adds a font attribute for the emoji and stores the original font in
+  // https://developer.apple.com/documentation/uikit/uitextinput/1614489-markedtextrange?language=objc for more info.
+  // Also, updating the attributed text while inputting Korean language will break input mechanism.
+  // If the user added an emoji, the system adds a font attribute for the emoji and stores the original font in
   // NSOriginalFont. Lastly, when entering a password, etc., there will be additional styling on the field as the native
   // text view handles showing the last character for a split second.
   __block BOOL fontHasBeenUpdatedBySystem = false;
@@ -633,6 +634,7 @@ - (BOOL)_textOf:(NSAttributedString *)newText equals:(NSAttributedString *)oldTe
 
   BOOL shouldFallbackToBareTextComparison =
       [_backedTextInputView.textInputMode.primaryLanguage isEqualToString:@"dictation"] ||
+      [_backedTextInputView.textInputMode.primaryLanguage isEqualToString:@"ko-KR"] ||
       _backedTextInputView.markedTextRange || _backedTextInputView.isSecureTextEntry || fontHasBeenUpdatedBySystem;
 
   if (shouldFallbackToBareTextComparison) {