Revert D4680300: [RN] BREAKING: Better TextInput: contentSize property was removed from <TextInput>.onChange event.

Differential Revision: D4680300

fbshipit-source-id: 20f7299c53cc54215fb333e97d7e11de087e303d

Libraries/Text/RCTTextView.m

@@ -489,6 +489,35 @@ static BOOL findMismatch(NSString *first, NSString *second, NSRange *firstRange,
 
   _nativeUpdatesInFlight = NO;
   _nativeEventCount++;
+
+  // TODO: t16435709 This part will be removed soon.
+  if (!self.reactTag || !_onChange) {
+    return;
+  }
+
+  // When the context size increases, iOS updates the contentSize twice; once
+  // with a lower height, then again with the correct height. To prevent a
+  // spurious event from being sent, we track the previous, and only send the
+  // update event if it matches our expectation that greater text length
+  // should result in increased height. This assumption is, of course, not
+  // necessarily true because shorter text might include more linebreaks, but
+  // in practice this works well enough.
+  NSUInteger textLength = textView.text.length;
+  CGFloat contentHeight = textView.contentSize.height;
+  if (textLength >= _previousTextLength) {
+    contentHeight = MAX(contentHeight, _previousContentHeight);
+  }
+  _previousTextLength = textLength;
+  _previousContentHeight = contentHeight;
+  _onChange(@{
+    @"text": self.text,
+    @"contentSize": @{
+      @"height": @(contentHeight),
+      @"width": @(textView.contentSize.width)
+    },
+    @"target": self.reactTag,
+    @"eventCount": @(_nativeEventCount),
+  });
 }
 
 - (void)textViewDidEndEditing:(UITextView *)textView