Create an experiment to remove extra collection teardown step

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Reduce usage of autorelease pools. [Adlai Holler](https://github.com/Adlai-Holler) [#968](https://github.com/TextureGroup/Texture/pull/968)
 - Clean up unused/unneeded header macros. [Adlai Holler](https://github.com/Adlai-Holler)
 - Clean up C-function `extern` decorators. [Adlai Holler](https://github.com/Adlai-Holler)
+- Add an experiment to reduce work involved in collection teardown. [Adlai Holler](https://github.com/Adlai-Holler)
 
 ## 2.7
 - Fix pager node for interface coalescing. [Max Wang](https://github.com/wsdwsd0829) [#877](https://github.com/TextureGroup/Texture/pull/877)

Schemas/configuration.json

@@ -19,7 +19,8 @@
                     "exp_unfair_lock",
                     "exp_infer_layer_defaults",
                     "exp_network_image_queue",
-                    "exp_dealloc_queue_v2"
+                    "exp_dealloc_queue_v2",
+                    "exp_collection_teardown",
                 ]
     		}
 		}

Source/ASCollectionView.mm

@@ -324,8 +324,10 @@ - (void)dealloc
 
   // Sometimes the UIKit classes can call back to their delegate even during deallocation, due to animation completion blocks etc.
   _isDeallocating = YES;
-  [self setAsyncDelegate:nil];
-  [self setAsyncDataSource:nil];
+  if (!ASActivateExperimentalFeature(ASExperimentalCollectionTeardown)) {
+    [self setAsyncDelegate:nil];
+    [self setAsyncDataSource:nil];
+  }
 
   // Data controller & range controller may own a ton of nodes, let's deallocate those off-main.
   ASPerformBackgroundDeallocation(&_dataController);

Source/ASExperimentalFeatures.h

@@ -26,6 +26,7 @@ typedef NS_OPTIONS(NSUInteger, ASExperimentalFeatures) {
   ASExperimentalLayerDefaults = 1 << 4,                     // exp_infer_layer_defaults
   ASExperimentalNetworkImageQueue = 1 << 5,                 // exp_network_image_queue
   ASExperimentalDeallocQueue = 1 << 6,                      // exp_dealloc_queue_v2
+  ASExperimentalCollectionTeardown = 1 << 7,                // exp_collection_teardown
   ASExperimentalFeatureAll = 0xFFFFFFFF
 };
 

Source/ASExperimentalFeatures.m

@@ -20,7 +20,8 @@
                                       @"exp_unfair_lock",
                                       @"exp_infer_layer_defaults",
                                       @"exp_network_image_queue",
-                                      @"exp_dealloc_queue_v2"]));
+                                      @"exp_dealloc_queue_v2",
+                                      @"exp_collection_teardown"]));
 
   if (flags == ASExperimentalFeatureAll) {
     return allNames;

Source/ASTableView.mm

@@ -24,6 +24,7 @@
 #import <AsyncDisplayKit/ASBatchFetching.h>
 #import <AsyncDisplayKit/ASCellNode+Internal.h>
 #import <AsyncDisplayKit/ASCollectionElement.h>
+#import <AsyncDisplayKit/ASConfigurationInternal.h>
 #import <AsyncDisplayKit/ASDelegateProxy.h>
 #import <AsyncDisplayKit/ASDisplayNodeExtras.h>
 #import <AsyncDisplayKit/ASDisplayNode+FrameworkPrivate.h>
@@ -371,8 +372,10 @@ - (void)dealloc
 
   // Sometimes the UIKit classes can call back to their delegate even during deallocation.
   _isDeallocating = YES;
-  [self setAsyncDelegate:nil];
-  [self setAsyncDataSource:nil];
+  if (!ASActivateExperimentalFeature(ASExperimentalCollectionTeardown)) {
+    [self setAsyncDelegate:nil];
+    [self setAsyncDataSource:nil];
+  }
 
   // Data controller & range controller may own a ton of nodes, let's deallocate those off-main
   ASPerformBackgroundDeallocation(&_dataController);

Source/Details/ASDataController.mm

@@ -930,6 +930,8 @@ - (void)clearData
   ASDisplayNodeAssertMainThread();
   if (_initialReloadDataHasBeenCalled) {
     [self waitUntilAllUpdatesAreProcessed];
+    auto vis = self.visibleMap;
+    auto pending = self.pendingMap;
     self.visibleMap = self.pendingMap = [[ASElementMap alloc] init];
   }
 }

Source/Details/ASDelegateProxy.h

@@ -34,7 +34,7 @@
 
 @interface ASDelegateProxy : NSProxy
 
-- (instancetype)initWithTarget:(id <NSObject>)target interceptor:(id <ASDelegateProxyInterceptor>)interceptor;
+- (instancetype)initWithTarget:(id)target interceptor:(id <ASDelegateProxyInterceptor>)interceptor;
 
 // This method must be overridden by a subclass.
 - (BOOL)interceptsSelector:(SEL)selector;

Source/Details/ASDelegateProxy.m

@@ -141,16 +141,11 @@ - (BOOL)interceptsSelector:(SEL)selector
 
 @implementation ASDelegateProxy {
   id <ASDelegateProxyInterceptor> __weak _interceptor;
-  id <NSObject> __weak _target;
+  id __weak _target;
 }
 
-- (instancetype)initWithTarget:(id <NSObject>)target interceptor:(id <ASDelegateProxyInterceptor>)interceptor
+- (instancetype)initWithTarget:(id)target interceptor:(id <ASDelegateProxyInterceptor>)interceptor
 {
-  // -[NSProxy init] is undefined
-  if (!self) {
-    return nil;
-  }
-
   ASDisplayNodeAssert(interceptor, @"interceptor must not be nil");
 
   _target = target ? : [NSNull null];
@@ -161,8 +156,9 @@ - (instancetype)initWithTarget:(id <NSObject>)target interceptor:(id <ASDelegate
 
 - (BOOL)conformsToProtocol:(Protocol *)aProtocol
 {
-  if (_target) {
-    return [_target conformsToProtocol:aProtocol];
+  id target = _target;
+  if (target) {
+    return [target conformsToProtocol:aProtocol];
   } else {
     return [super conformsToProtocol:aProtocol];
   }
@@ -183,8 +179,9 @@ - (id)forwardingTargetForSelector:(SEL)aSelector
   if ([self interceptsSelector:aSelector]) {
     return _interceptor;
   } else {
-    if (_target) {
-      return [_target respondsToSelector:aSelector] ? _target : nil;
+    id target = _target;
+    if (target) {
+      return [target respondsToSelector:aSelector] ? target : nil;
     } else {
       // The _interceptor needs to be nilled out in this scenario. For that a strong reference needs to be created
       // to be able to nil out the _interceptor but still let it know that the proxy target has deallocated