[Text] Fix color defaults for light/dark mode (facebook#538)

Author: alloy

Libraries/Text/RCTTextAttributes.m

@@ -31,6 +31,9 @@ - (instancetype)init
     _textShadowRadius = NAN;
     _opacity = NAN;
     _textTransform = RCTTextTransformUndefined;
+#if TARGET_OS_OSX // TODO(macOS ISS#2323203)
+    _foregroundColor = [NSColor labelColor];
+#endif // TODO(macOS ISS#2323203)
   }
 
   return self;

Libraries/Text/TextInput/Multiline/RCTUITextView.m

@@ -30,8 +30,7 @@ @implementation RCTUITextView
 
 static RCTUIColor *defaultPlaceholderColor() // TODO(OSS Candidate ISS#2710739)
 {
-  // Default placeholder color from UITextField.
-  return [RCTUIColor colorWithRed:0 green:0 blue:0.0980392 alpha:0.22]; // TODO(OSS Candidate ISS#2710739)
+  return [RCTUIColor placeholderTextColor]; // TODO(OSS Candidate ISS#2710739)
 }
 
 - (instancetype)initWithFrame:(CGRect)frame
@@ -227,7 +226,7 @@ - (void)setAttributedText:(NSAttributedString *)attributedText
       [self.textStorage setAttributedString:[NSAttributedString new]];
     }
   } else {
-  // But if the text is preserved, we just copying the attributes from the source string.
+    // But if the text is preserved, we just copy the attributes from the source string.
     if (![self.textStorage isEqualToAttributedString:attributedText]) {
       [self copyTextAttributesFrom:attributedText];
     }

Libraries/Text/TextInput/Singleline/RCTUITextField.m

@@ -320,7 +320,11 @@ - (void)setSecureTextEntry:(BOOL)secureTextEntry
   if (self.placeholderColor) {
     [textAttributes setValue:self.placeholderColor forKey:NSForegroundColorAttributeName];
   } else {
+#if TARGET_OS_OSX // [TODO(macOS ISS#2323203)
+    [textAttributes setValue:defaultPlaceholderTextColor() forKey:NSForegroundColorAttributeName];
+#else
     [textAttributes removeObjectForKey:NSForegroundColorAttributeName];
+#endif // ]TODO(macOS ISS#2323203)
   }
 
   return textAttributes;