From 34c935c1a5fee83283beece8f1c6b3d6344f275d Mon Sep 17 00:00:00 2001
From: Maxime Ollivier <maxo@fb.com>
Date: Fri, 26 Jun 2020 10:03:47 -0700
Subject: [PATCH] clean up IGListExperimentGetCollectionViewAtUpdate

Summary: Experiment shipped.

Reviewed By: Haud, lorixx

Differential Revision: D22219242

fbshipit-source-id: 60dbb5f008656ae67b02294ef16138703ebe392f
---
 CHANGELOG.md                             |  2 ++
 Source/IGListDiffKit/IGListExperiments.h |  4 +---
 Source/IGListKit/IGListAdapter.m         | 12 +++---------
 Tests/IGListAdapterE2ETests.m            |  4 ----
 4 files changed, 6 insertions(+), 16 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8da30863b..c270140ff 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,8 @@ The changelog for `IGListKit`. Also see the [releases](https://github.com/instag
 
 - Fixed missing update when calling `performUpdatesAnimated` multiple times quickly and using the `reloadDataFallback()`. [Maxime Ollivier](https://github.com/maxolls) (tbd)
 
+- Request the `UICollectionView` until just-before we update. This way if the `UICollectionView` is changed between update-queue and execution, we guarantee the update is performed on the correct view. Ship with experiment `IGListExperimentGetCollectionViewAtUpdate` from Ryan Nystrom. [Maxime Ollivier](https://github.com/maxolls) (tbd)
+
 4.0.0
 -----
 ### Breaking Changes
diff --git a/Source/IGListDiffKit/IGListExperiments.h b/Source/IGListDiffKit/IGListExperiments.h
index 852150c8e..77d7f2824 100644
--- a/Source/IGListDiffKit/IGListExperiments.h
+++ b/Source/IGListDiffKit/IGListExperiments.h
@@ -22,10 +22,8 @@ typedef NS_OPTIONS (NSInteger, IGListExperiment) {
     IGListExperimentReloadDataFallback = 1 << 3,
     /// Test deferring object creation until just before diffing.
     IGListExperimentDeferredToObjectCreation = 1 << 4,
-    /// Test getting collection view at update time.
-    IGListExperimentGetCollectionViewAtUpdate = 1 << 5,
     /// Test invalidating layout when cell reloads/updates in IGListBindingSectionController.
-    IGListExperimentInvalidateLayoutForUpdates = 1 << 6,
+    IGListExperimentInvalidateLayoutForUpdates = 1 << 5,
 };
 
 /**
diff --git a/Source/IGListKit/IGListAdapter.m b/Source/IGListKit/IGListAdapter.m
index 645c844f0..8f61d6169 100644
--- a/Source/IGListKit/IGListAdapter.m
+++ b/Source/IGListKit/IGListAdapter.m
@@ -107,8 +107,7 @@ - (void)setCollectionView:(UICollectionView *)collectionView {
         [self _updateCollectionViewDelegate];
 
         // only construct
-        if (!IGListExperimentEnabled(self.experiments, IGListExperimentGetCollectionViewAtUpdate)
-            || settingFirstCollectionView) {
+        if (settingFirstCollectionView) {
             [self _updateAfterPublicSettingsChange];
         }
     }
@@ -573,13 +572,8 @@ - (CGSize)sizeForSupplementaryViewOfKind:(NSString *)elementKind atIndexPath:(NS
 #pragma mark - Private API
 
 - (IGListCollectionViewBlock)_collectionViewBlock {
-    if (IGListExperimentEnabled(self.experiments, IGListExperimentGetCollectionViewAtUpdate)) {
-        __weak __typeof__(self) weakSelf = self;
-        return ^UICollectionView *{ return weakSelf.collectionView; };
-    } else {
-        __weak UICollectionView *collectionView = _collectionView;
-        return ^UICollectionView *{ return collectionView; };
-    }
+     __weak __typeof__(self) weakSelf = self;
+    return ^UICollectionView *{ return weakSelf.collectionView; };
 }
 
 // this method is what updates the "source of truth"
diff --git a/Tests/IGListAdapterE2ETests.m b/Tests/IGListAdapterE2ETests.m
index 4d39044f1..d98a5ae7f 100644
--- a/Tests/IGListAdapterE2ETests.m
+++ b/Tests/IGListAdapterE2ETests.m
@@ -1841,7 +1841,6 @@ - (void)test_whenModifyingInitialAndFinalAttribute_thatLayoutIsCorrect {
 - (void)test_whenSwappingCollectionViewsAfterUpdate_thatUpdatePerformedOnTheCorrectCollectionView {
     // BEGIN: setup of FIRST adapter+dataSource+collectionView
     IGListAdapter *adapter1 = [[IGListAdapter alloc] initWithUpdater:[IGListAdapterUpdater new] viewController:nil];
-    adapter1.experiments |= IGListExperimentGetCollectionViewAtUpdate;
 
     UICollectionView *collectionView1 = [[UICollectionView alloc] initWithFrame:self.window.frame collectionViewLayout:[UICollectionViewFlowLayout new]];
     [self.window addSubview:collectionView1];
@@ -1857,7 +1856,6 @@ - (void)test_whenSwappingCollectionViewsAfterUpdate_thatUpdatePerformedOnTheCorr
 
     // BEGIN: setup of SECOND adapter+dataSource+collectionView
     IGListAdapter *adapter2 = [[IGListAdapter alloc] initWithUpdater:[IGListAdapterUpdater new] viewController:nil];
-    adapter2.experiments |= IGListExperimentGetCollectionViewAtUpdate;
 
     UICollectionView *collectionView2 = [[UICollectionView alloc] initWithFrame:self.window.frame collectionViewLayout:[UICollectionViewFlowLayout new]];
     [self.window addSubview:collectionView2];
@@ -1891,7 +1889,6 @@ - (void)test_whenCollectionViewBecomesNilDuringPerformUpdates_thatStateCleanedCo
     [self setupWithObjects:@[
                              genTestObject(@1, @1)
                              ]];
-    self.adapter.experiments |= IGListExperimentGetCollectionViewAtUpdate;
 
     // perform update on listAdapter
     XCTestExpectation *expectation1 = genExpectation;
@@ -1938,7 +1935,6 @@ - (void)test_whenCollectionViewBecomesNilDuringReloadData_thatStateCleanedCorrec
     [self setupWithObjects:@[
                              genTestObject(@1, @1)
                              ]];
-    self.adapter.experiments |= IGListExperimentGetCollectionViewAtUpdate;
 
     // reload data on listAdapter
     XCTestExpectation *expectation1 = genExpectation;