Remove integration between Paper and Fabric's UIManager

Summary:
Changelog: [Internal]

In D8552360 (facebook@48b9a6f) an experimental integration between old and new UIManager has been introduced.
It isn't needed anymore.

I did some measurements and it is the slowest part of `[RCTComponentViewDescriptor dequeueComponentViewWithComponentHandle]`.

{F241943384}

Reviewed By: shergin

Differential Revision: D22274782

fbshipit-source-id: 799ba047f1c57f68f00b0b6fa7c58782874991bc

Author: sammy-SC

React/Fabric/Mounting/RCTComponentViewRegistry.mm

@@ -18,60 +18,6 @@
 
 using namespace facebook::react;
 
-#define LEGACY_UIMANAGER_INTEGRATION_ENABLED 1
-
-#ifdef LEGACY_UIMANAGER_INTEGRATION_ENABLED
-
-#import <React/RCTBridge+Private.h>
-#import <React/RCTUIManager.h>
-
-/**
- * Warning: This is a total hack and temporary solution.
- * Unless we have a pure Fabric-based implementation of UIManager commands
- * delivery pipeline, we have to leverage existing infra. This code tricks
- * legacy UIManager by registering all Fabric-managed views in it,
- * hence existing command-delivery infra can reach "foreign" views using
- * the old pipeline.
- */
-@interface RCTUIManager ()
-- (NSMutableDictionary<NSNumber *, UIView *> *)viewRegistry;
-@end
-
-@interface RCTUIManager (Hack)
-
-+ (void)registerView:(UIView *)view;
-+ (void)unregisterView:(UIView *)view;
-
-@end
-
-@implementation RCTUIManager (Hack)
-
-+ (void)registerView:(UIView *)view
-{
-  if (!view) {
-    return;
-  }
-
-  RCTUIManager *uiManager = [[RCTBridge currentBridge] uiManager];
-  view.reactTag = @(view.tag);
-  [uiManager.viewRegistry setObject:view forKey:@(view.tag)];
-}
-
-+ (void)unregisterView:(UIView *)view
-{
-  if (!view) {
-    return;
-  }
-
-  RCTUIManager *uiManager = [[RCTBridge currentBridge] uiManager];
-  view.reactTag = nil;
-  [uiManager.viewRegistry removeObjectForKey:@(view.tag)];
-}
-
-@end
-
-#endif
-
 const NSInteger RCTComponentViewRegistryRecyclePoolMaxSize = 1024;
 
 @implementation RCTComponentViewRegistry {
@@ -133,10 +79,6 @@ - (RCTComponentViewDescriptor)dequeueComponentViewWithComponentHandle:(Component
 
   _registry.insert({tag, componentViewDescriptor});
 
-#ifdef LEGACY_UIMANAGER_INTEGRATION_ENABLED
-  [RCTUIManager registerView:componentViewDescriptor.view];
-#endif
-
   return componentViewDescriptor;
 }
 
@@ -149,10 +91,6 @@ - (void)enqueueComponentViewWithComponentHandle:(ComponentHandle)componentHandle
   RCTAssert(
       _registry.find(tag) != _registry.end(), @"RCTComponentViewRegistry: Attempt to enqueue unregistered component.");
 
-#ifdef LEGACY_UIMANAGER_INTEGRATION_ENABLED
-  [RCTUIManager unregisterView:componentViewDescriptor.view];
-#endif
-
   _registry.erase(tag);
   componentViewDescriptor.view.tag = 0;
   [self _enqueueComponentViewWithComponentHandle:componentHandle componentViewDescriptor:componentViewDescriptor];

React/Fabric/RCTSurfacePresenter.h

@@ -75,6 +75,11 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (void)removeObserver:(id<RCTSurfacePresenterObserver>)observer;
 
+/*
+ * Please do not use this, this will be deleted soon.
+ */
+- (nullable UIView *)findComponentViewWithTag_DO_NOT_USE_DEPRECATED:(NSInteger)tag;
+
 @end
 
 NS_ASSUME_NONNULL_END

React/Fabric/RCTSurfacePresenter.mm

@@ -189,6 +189,13 @@ - (void)setMinimumSize:(CGSize)minimumSize maximumSize:(CGSize)maximumSize surfa
                                                 surfaceId:surface.rootTag];
 }
 
+- (UIView *)findComponentViewWithTag_DO_NOT_USE_DEPRECATED:(NSInteger)tag
+{
+  UIView<RCTComponentViewProtocol> *componentView =
+      [_mountingManager.componentViewRegistry findComponentViewWithTag:tag];
+  return componentView;
+}
+
 - (BOOL)synchronouslyUpdateViewOnUIThread:(NSNumber *)reactTag props:(NSDictionary *)props
 {
   RCTScheduler *scheduler = [self _scheduler];

React/Modules/RCTSurfacePresenterStub.h

@@ -26,6 +26,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @protocol RCTSurfacePresenterStub <NSObject>
 
+- (nullable UIView *)findComponentViewWithTag_DO_NOT_USE_DEPRECATED:(NSInteger)tag;
 - (BOOL)synchronouslyUpdateViewOnUIThread:(NSNumber *)reactTag props:(NSDictionary *)props;
 - (void)addObserver:(id<RCTSurfacePresenterObserver>)observer;
 - (void)removeObserver:(id<RCTSurfacePresenterObserver>)observer;

React/Modules/RCTUIManager.m

@@ -8,6 +8,7 @@
 #import "RCTUIManager.h"
 
 #import <AVFoundation/AVFoundation.h>
+#import <React/RCTSurfacePresenterStub.h>
 
 #import "RCTAssert.h"
 #import "RCTBridge+Private.h"
@@ -354,7 +355,11 @@ - (NSString *)viewNameForReactTag:(NSNumber *)reactTag
 - (UIView *)viewForReactTag:(NSNumber *)reactTag
 {
   RCTAssertMainQueue();
-  return _viewRegistry[reactTag];
+  UIView *view = [_bridge.surfacePresenter findComponentViewWithTag_DO_NOT_USE_DEPRECATED:reactTag.integerValue];
+  if (!view) {
+    view = _viewRegistry[reactTag];
+  }
+  return view;
 }
 
 - (RCTShadowView *)shadowViewForReactTag:(NSNumber *)reactTag