Add a mechanism to separate internal and external default experiments

Summary:
This diff provides a temporary mechanism to allow different experiments to be enabled by default between internal and external builds of IGListKit. It works similarly to `IGListAssert` where a different copy of `IGListDefaultExperiments.h` is provided by BUCK when performing internal builds.

For the open source copies of IGListKit, the standard system behaviour of triggering an `NSInconsistencyException` when an invalid batch transaction occurs is set. For internal builds, the `IGListExperimentThrowOnInconsistencyException` experiment is disabled, where invalid transactions are forwarded to `IGListAssert` instead.

Differential Revision: D54571550

fbshipit-source-id: c6c339de20c24eb487846b6567d6c8bc08bc20f2

IGListKit.xcodeproj/project.pbxproj

@@ -420,6 +420,8 @@
 		E8D312E01FC472A60009FA2F /* IGListContentInsetTests.m in Sources */ = {isa = PBXBuildFile; fileRef = E8D312DF1FC472A60009FA2F /* IGListContentInsetTests.m */; };
 		F102DBBB2ACE4CD500394DB7 /* IGListArrayUtilsInternal.m in Sources */ = {isa = PBXBuildFile; fileRef = F102DBBA2ACE4CD500394DB7 /* IGListArrayUtilsInternal.m */; };
 		F102DBBC2ACE4CD500394DB7 /* IGListArrayUtilsInternal.m in Sources */ = {isa = PBXBuildFile; fileRef = F102DBBA2ACE4CD500394DB7 /* IGListArrayUtilsInternal.m */; };
+		F10C8F572B982EE6009F4690 /* IGListDefaultExperiments.h in Headers */ = {isa = PBXBuildFile; fileRef = F10C8F562B982DFD009F4690 /* IGListDefaultExperiments.h */; };
+		F10C8F582B982EE7009F4690 /* IGListDefaultExperiments.h in Headers */ = {isa = PBXBuildFile; fileRef = F10C8F562B982DFD009F4690 /* IGListDefaultExperiments.h */; };
 		F10C8F5B2B9830F0009F4690 /* IGListTestCollectionViewLayout.m in Sources */ = {isa = PBXBuildFile; fileRef = F10C8F592B9830E6009F4690 /* IGListTestCollectionViewLayout.m */; };
 		F10C8F5C2B9830F1009F4690 /* IGListTestCollectionViewLayout.m in Sources */ = {isa = PBXBuildFile; fileRef = F10C8F592B9830E6009F4690 /* IGListTestCollectionViewLayout.m */; };
 		F1855A4C29BC565600558D18 /* IGListDiffDescriptionStringTests.m in Sources */ = {isa = PBXBuildFile; fileRef = F1855A4B29BC565600558D18 /* IGListDiffDescriptionStringTests.m */; };
@@ -753,6 +755,7 @@
 		E56B7B3320A9D7100071010C /* IGListCollectionScrollingTraitsTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = IGListCollectionScrollingTraitsTests.m; sourceTree = "<group>"; };
 		E8D312DF1FC472A60009FA2F /* IGListContentInsetTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = IGListContentInsetTests.m; sourceTree = "<group>"; };
 		F102DBBA2ACE4CD500394DB7 /* IGListArrayUtilsInternal.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = IGListArrayUtilsInternal.m; sourceTree = "<group>"; };
+		F10C8F562B982DFD009F4690 /* IGListDefaultExperiments.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = IGListDefaultExperiments.h; sourceTree = "<group>"; };
 		F10C8F592B9830E6009F4690 /* IGListTestCollectionViewLayout.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = IGListTestCollectionViewLayout.m; sourceTree = "<group>"; };
 		F10C8F5A2B9830E6009F4690 /* IGListTestCollectionViewLayout.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = IGListTestCollectionViewLayout.h; sourceTree = "<group>"; };
 		F1855A4B29BC565600558D18 /* IGListDiffDescriptionStringTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = IGListDiffDescriptionStringTests.m; sourceTree = "<group>"; };
@@ -967,6 +970,7 @@
 				7A02CF892361513500B49FAE /* IGListDebugger.m */,
 				7A02CF832361513500B49FAE /* IGListDebuggingUtilities.h */,
 				7A02CF8B2361513500B49FAE /* IGListDebuggingUtilities.m */,
+				F10C8F562B982DFD009F4690 /* IGListDefaultExperiments.h */,
 				7A02CF642361513300B49FAE /* IGListDisplayHandler.h */,
 				7A02CF802361513500B49FAE /* IGListDisplayHandler.m */,
 				57B22E7C2502AAC40055DC2F /* IGListItemUpdatesCollector.h */,
@@ -1339,6 +1343,7 @@
 				7A02CFA92361513600B49FAE /* UICollectionViewLayout+InteractiveReordering.h in Headers */,
 				E03DEA83255C9AAC00ACCAFC /* IGListTransitionData.h in Headers */,
 				0A89290026CDA632003FABD8 /* IGListBatchUpdateTransaction.h in Headers */,
+				F10C8F582B982EE7009F4690 /* IGListDefaultExperiments.h in Headers */,
 				0A8928FB26CDA591003FABD8 /* IGListReloadTransaction.h in Headers */,
 				0A8928FA26CDA53B003FABD8 /* IGListUpdateTransactionBuilder.h in Headers */,
 				0A8928FE26CDA5EA003FABD8 /* IGListDataSourceChangeTransaction.h in Headers */,
@@ -1410,6 +1415,7 @@
 				7A02CF452361511100B49FAE /* IGListAdapterPerformanceDelegate.h in Headers */,
 				7A02D0022361513600B49FAE /* IGListSectionControllerInternal.h in Headers */,
 				7A02CFC92361513600B49FAE /* UICollectionView+IGListBatchUpdateData.h in Headers */,
+				F10C8F572B982EE6009F4690 /* IGListDefaultExperiments.h in Headers */,
 				7A02CEF12361511100B49FAE /* IGListScrollDelegate.h in Headers */,
 				7A02CFF62361513600B49FAE /* IGListSectionMap+DebugDescription.h in Headers */,
 				F18CC76A29EFBD0300DC3B9A /* IGListBindingSingleSectionController.h in Headers */,

Source/IGListKit/IGListAdapter.m

@@ -13,11 +13,12 @@
 #import <IGListDiffKit/IGListAssert.h>
 #endif
 #import "IGListAdapterUpdater.h"
-#import "IGListSupplementaryViewSource.h"
 
 #import "IGListArrayUtilsInternal.h"
 #import "IGListDebugger.h"
+#import "IGListDefaultExperiments.h"
 #import "IGListSectionControllerInternal.h"
+#import "IGListSupplementaryViewSource.h"
 #import "IGListTransitionData.h"
 #import "IGListUpdatingDelegate.h"
 #import "UICollectionViewLayout+InteractiveReordering.h"
@@ -64,6 +65,8 @@ - (instancetype)initWithUpdater:(id <IGListUpdatingDelegate>)updater
         _updater = updater;
         _viewController = viewController;
 
+        _experiments = IGListDefaultExperiments();
+
         [IGListDebugger trackAdapter:self];
     }
     return self;

Source/IGListKit/IGListAdapterUpdater.m

@@ -14,6 +14,7 @@
 #endif
 
 #import "IGListAdapterUpdaterHelpers.h"
+#import "IGListDefaultExperiments.h"
 #import "IGListIndexSetResultInternal.h"
 #import "IGListMoveIndexPathInternal.h"
 #import "IGListReloadIndexPath.h"
@@ -37,6 +38,7 @@ - (instancetype)init {
     if (self = [super init]) {
         _transactionBuilder = [IGListUpdateTransactionBuilder new];
         _allowsReloadingOnTooManyUpdates = YES;
+        _experiments = IGListDefaultExperiments();
     }
     return self;
 }

Source/IGListKit/Internal/IGListDefaultExperiments.h

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#import <Foundation/Foundation.h>
+
+#if __has_include(<IGListDiffKit/IGListDiffKit.h>)
+#import <IGListDiffKit/IGListExperiments.h>
+#else
+#import "IGListExperiments.h"
+#endif
+
+/// Provides a list of experiments that are enabled by default in IGListKit.
+static inline IGListExperiment IGListDefaultExperiments(void) {
+    return IGListExperimentThrowOnInconsistencyException;
+}