Workaround crash during layout on macOS when a large number of flex (facebook#69)

layouts are being performed, such as during a window resize.

Author: tom-un

Libraries/Text/Text/RCTTextView.m

@@ -115,6 +115,20 @@ - (void)setTextStorage:(NSTextStorage *)textStorage
           contentFrame:(CGRect)contentFrame
        descendantViews:(NSArray<UIView *> *)descendantViews
 {
+#if TARGET_OS_OSX // [TODO(macOS ISS#2323203)
+  // On macOS when a large number of flex layouts are being performed, such
+  // as when a window is being resized, AppKit can throw an uncaught exception
+  // (-[NSConcretePointerArray pointerAtIndex:]: attempt to access pointer at index ...)
+  // during the dealloc of NSLayoutManager.  The _textStorage and its
+  // associated NSLayoutManager dealloc later in an autorelease pool.
+  // Manually removing the layout manager from _textStorage prior to release
+  // works around this issue in AppKit.
+  NSArray<NSLayoutManager *> *managers = [_textStorage layoutManagers];
+  for (NSLayoutManager *manager in managers) {
+    [_textStorage removeLayoutManager:manager];
+  }
+#endif // ]TODO(macOS ISS#2323203)
+
   _textStorage = textStorage;
   _contentFrame = contentFrame;