Fix Xcode warnings in React-Core pod (#29622)

Summary:
With the upgrade to React Native 0.63, we started running into nullability warnings that were breaking our build. This PR fixes those nullability warnings as well as a few other warnings in React-Core.

## Changelog

<!-- Help reviewers and the release process by writing your own changelog entry. For example, see:
https://github.com/facebook/react-native/wiki/Changelog
-->

[iOS] [Fixed] - Fix xcodebuild warnings in React-Core

Pull Request resolved: #29622

Test Plan:
- Nullability annotations should only affect compilation, but even though RNTester compiles, I'm not fully convinced that this won't break projects downstream. It would be good to get another opinion on this.
- The change in `RCTAllocateRootViewTag` is the only real logic change in this PR. We throw an exception if the root view tag is not in the correct format, so this change seems safe after some basic manual testing in RNTester.

Reviewed By: shergin

Differential Revision: D23386678

Pulled By: appden

fbshipit-source-id: a74875195a4614c3248e8f968aa98602e3ee2de0

Libraries/Image/RCTImageLoaderProtocol.h

@@ -14,6 +14,8 @@
 #import <React/RCTImageURLLoader.h>
 #import <React/RCTImageCache.h>
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  * If available, RCTImageRedirectProtocol is invoked before loading an asset.
  * Implementation should return either a new URL or nil when redirection is
@@ -132,3 +134,5 @@ typedef NS_ENUM(NSUInteger, RCTImageLoaderPriority) {
 - (void)setImageCache:(id<RCTImageCache>)cache;
 
 @end
+
+NS_ASSUME_NONNULL_END

Libraries/Image/RCTImageURLLoader.h

@@ -10,9 +10,11 @@
 #import <React/RCTBridge.h>
 #import <React/RCTResizeMode.h>
 
+NS_ASSUME_NONNULL_BEGIN
+
 typedef void (^RCTImageLoaderProgressBlock)(int64_t progress, int64_t total);
 typedef void (^RCTImageLoaderPartialLoadBlock)(UIImage *image);
-typedef void (^RCTImageLoaderCompletionBlock)(NSError *error, UIImage *image);
+typedef void (^RCTImageLoaderCompletionBlock)(NSError * _Nullable error, UIImage * _Nullable image);
 typedef dispatch_block_t RCTImageLoaderCancellationBlock;
 
 /**
@@ -71,3 +73,5 @@ typedef dispatch_block_t RCTImageLoaderCancellationBlock;
 - (BOOL)shouldCacheLoadedImages;
 
 @end
+
+NS_ASSUME_NONNULL_END

React/Base/RCTBridge.m

@@ -218,7 +218,24 @@ - (void)setRCTTurboModuleRegistry:(id<RCTTurboModuleRegistry>)turboModuleRegistr
 
 - (void)didReceiveReloadCommand
 {
-  [self reloadWithReason:@"Command"];
+#if RCT_ENABLE_INSPECTOR
+  // Disable debugger to resume the JsVM & avoid thread locks while reloading
+  [RCTInspectorDevServerHelper disableDebugger];
+#endif
+
+  [[NSNotificationCenter defaultCenter] postNotificationName:RCTBridgeWillReloadNotification object:self userInfo:nil];
+
+  /**
+   * Any thread
+   */
+  dispatch_async(dispatch_get_main_queue(), ^{
+    // WARNING: Invalidation is async, so it may not finish before re-setting up the bridge,
+    // causing some issues. TODO: revisit this post-Fabric/TurboModule.
+    [self invalidate];
+    // Reload is a special case, do not preserve launchOptions and treat reload as a fresh start
+    self->_launchOptions = nil;
+    [self setUp];
+  });
 }
 
 - (NSArray<Class> *)moduleClasses
@@ -269,32 +286,15 @@ - (BOOL)moduleIsInitialized:(Class)moduleClass
  */
 - (void)reload
 {
-  [self reloadWithReason:@"Unknown from bridge"];
+  RCTTriggerReloadCommandListeners(@"Unknown from bridge");
 }
 
 /**
  * DEPRECATED - please use RCTReloadCommand.
  */
 - (void)reloadWithReason:(NSString *)reason
 {
-#if RCT_ENABLE_INSPECTOR
-  // Disable debugger to resume the JsVM & avoid thread locks while reloading
-  [RCTInspectorDevServerHelper disableDebugger];
-#endif
-
-  [[NSNotificationCenter defaultCenter] postNotificationName:RCTBridgeWillReloadNotification object:self userInfo:nil];
-
-  /**
-   * Any thread
-   */
-  dispatch_async(dispatch_get_main_queue(), ^{
-    // WARNING: Invalidation is async, so it may not finish before re-setting up the bridge,
-    // causing some issues. TODO: revisit this post-Fabric/TurboModule.
-    [self invalidate];
-    // Reload is a special case, do not preserve launchOptions and treat reload as a fresh start
-    self->_launchOptions = nil;
-    [self setUp];
-  });
+  RCTTriggerReloadCommandListeners(reason);
 }
 
 - (void)onFastRefresh

React/Base/RCTJSStackFrame.h

@@ -13,13 +13,13 @@
 @property (nonatomic, copy, readonly) NSString *file;
 @property (nonatomic, readonly) NSInteger lineNumber;
 @property (nonatomic, readonly) NSInteger column;
-@property (nonatomic, readonly) NSInteger collapse;
+@property (nonatomic, readonly) BOOL collapse;
 
 - (instancetype)initWithMethodName:(NSString *)methodName
                               file:(NSString *)file
                         lineNumber:(NSInteger)lineNumber
                             column:(NSInteger)column
-                          collapse:(NSInteger)collapse;
+                          collapse:(BOOL)collapse;
 - (NSDictionary *)toDictionary;
 
 + (instancetype)stackFrameWithLine:(NSString *)line;

React/Base/RCTJSStackFrame.m

@@ -57,7 +57,7 @@ - (instancetype)initWithMethodName:(NSString *)methodName
                               file:(NSString *)file
                         lineNumber:(NSInteger)lineNumber
                             column:(NSInteger)column
-                          collapse:(NSInteger)collapse
+                          collapse:(BOOL)collapse
 {
   if (self = [super init]) {
     _methodName = methodName;
@@ -100,7 +100,7 @@ + (instancetype)stackFrameWithLine:(NSString *)line
                                      file:file
                                lineNumber:[lineNumber integerValue]
                                    column:[column integerValue]
-                                 collapse:@NO];
+                                 collapse:NO];
 }
 
 + (instancetype)stackFrameWithDictionary:(NSDictionary *)dict
@@ -109,7 +109,7 @@ + (instancetype)stackFrameWithDictionary:(NSDictionary *)dict
                                      file:dict[@"file"]
                                lineNumber:[RCTNilIfNull(dict[@"lineNumber"]) integerValue]
                                    column:[RCTNilIfNull(dict[@"column"]) integerValue]
-                                 collapse:[RCTNilIfNull(dict[@"collapse"]) integerValue]];
+                                 collapse:[RCTNilIfNull(dict[@"collapse"]) boolValue]];
 }
 
 + (NSArray<RCTJSStackFrame *> *)stackFramesWithLines:(NSString *)lines

React/Base/RCTKeyCommands.m

@@ -113,7 +113,7 @@ + (void)initialize
 - (void)handleKeyUIEventSwizzle:(UIEvent *)event
 {
   NSString *modifiedInput = nil;
-  UIKeyModifierFlags *modifierFlags = nil;
+  UIKeyModifierFlags modifierFlags = 0;
   BOOL isKeyDown = NO;
 
   if ([event respondsToSelector:@selector(_modifiedInput)]) {

React/Base/RCTModuleData.h

@@ -97,4 +97,4 @@ typedef id<RCTBridgeModule> (^RCTBridgeModuleProvider)(void);
 @end
 
 RCT_EXTERN void RCTSetIsMainQueueExecutionOfConstantsToExportDisabled(BOOL val);
-RCT_EXTERN BOOL RCTIsMainQueueExecutionOfConstantsToExportDisabled();
+RCT_EXTERN BOOL RCTIsMainQueueExecutionOfConstantsToExportDisabled(void);

React/CxxBridge/RCTCxxBridge.mm

@@ -1119,26 +1119,6 @@ - (void)setUp
 {
 }
 
-- (void)reload
-{
-  if (!_valid) {
-    RCTLogWarn(
-        @"Attempting to reload bridge before it's valid: %@. Try restarting the development server if connected.",
-        self);
-  }
-  RCTTriggerReloadCommandListeners(@"Unknown from cxx bridge");
-}
-
-- (void)reloadWithReason:(NSString *)reason
-{
-  if (!_valid) {
-    RCTLogWarn(
-        @"Attempting to reload bridge before it's valid: %@. Try restarting the development server if connected.",
-        self);
-  }
-  RCTTriggerReloadCommandListeners(reason);
-}
-
 - (Class)executorClass
 {
   return _parentBridge.executorClass;

React/Modules/RCTUIManagerUtils.m

@@ -7,7 +7,7 @@
 
 #import "RCTUIManagerUtils.h"
 
-#import <libkern/OSAtomic.h>
+#import <stdatomic.h>
 
 #import "RCTAssert.h"
 
@@ -98,6 +98,6 @@ void RCTUnsafeExecuteOnUIManagerQueueSync(dispatch_block_t block)
 NSNumber *RCTAllocateRootViewTag()
 {
   // Numbering of these tags goes from 1, 11, 21, 31, ..., 100501, ...
-  static int64_t rootViewTagCounter = -1;
-  return @(OSAtomicIncrement64(&rootViewTagCounter) * 10 + 1);
+  static _Atomic int64_t rootViewTagCounter = 0;
+  return @(atomic_fetch_add_explicit(&rootViewTagCounter, 1, memory_order_relaxed) * 10 + 1);
 }

React/Profiler/RCTProfile.m

@@ -22,6 +22,7 @@
 #import "RCTDefines.h"
 #import "RCTLog.h"
 #import "RCTModuleData.h"
+#import "RCTReloadCommand.h"
 #import "RCTUIManager.h"
 #import "RCTUIManagerUtils.h"
 #import "RCTUtils.h"
@@ -378,7 +379,7 @@ + (void)vsync:(CADisplayLink *)displayLink
 
 + (void)reload
 {
-  [RCTProfilingBridge() reloadWithReason:@"Profiling controls"];
+  RCTTriggerReloadCommandListeners(@"Profiling controls");
 }
 
 + (void)toggle:(UIButton *)target

React/Views/RCTComponentData.h

@@ -15,6 +15,8 @@
 @class RCTShadowView;
 @class UIView;
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface RCTComponentData : NSObject
 
 @property (nonatomic, readonly) Class managerClass;
@@ -23,7 +25,7 @@
 
 - (instancetype)initWithManagerClass:(Class)managerClass bridge:(RCTBridge *)bridge NS_DESIGNATED_INITIALIZER;
 
-- (UIView *)createViewWithTag:(NSNumber *)tag rootTag:(NSNumber *)rootTag;
+- (UIView *)createViewWithTag:(nullable NSNumber *)tag rootTag:(nullable NSNumber *)rootTag;
 - (RCTShadowView *)createShadowViewWithTag:(NSNumber *)tag;
 - (void)setProps:(NSDictionary<NSString *, id> *)props forView:(id<RCTComponent>)view;
 - (void)setProps:(NSDictionary<NSString *, id> *)props forShadowView:(RCTShadowView *)shadowView;
@@ -34,3 +36,5 @@
 - (NSDictionary<NSString *, id> *)viewConfig;
 
 @end
+
+NS_ASSUME_NONNULL_END

React/Views/RCTComponentData.m

@@ -63,7 +63,7 @@ - (RCTViewManager *)manager
 
 RCT_NOT_IMPLEMENTED(-(instancetype)init)
 
-- (UIView *)createViewWithTag:(NSNumber *)tag rootTag:(NSNumber *)rootTag
+- (UIView *)createViewWithTag:(nullable NSNumber *)tag rootTag:(nullable NSNumber *)rootTag
 {
   RCTAssertMainQueue();