ship IGListExperimentSkipLayoutBeforeUpdate

Summary: Experiment looks good, so lets ship.

Reviewed By: patters

Differential Revision: D23145775

fbshipit-source-id: 16da69f220a2247490bb99b4965bcba33f498ced

CHANGELOG.md

@@ -26,6 +26,8 @@ The changelog for `IGListKit`. Also see the [releases](https://github.com/instag
 
 - Remove `[collectionView layoutIfNeeded]` before scrolling in `[IGListAdapter scrollToObject...]` to avoid creating off-screen cells. [Maxime Ollivier](https://github.com/maxolls) (tbd)
 
+- Remove `[collectionView layoutIfNeeded]` before updating in `[IGListAdapterUpdater performBatchUpdates...]` to fix occasional glitches. [Maxime Ollivier](https://github.com/maxolls) (tbd)
+
 - Fixed `IGListAdapterUpdaterDelegate` by 1) calling `willReloadDataWithCollectionView` on fallback reloads and 2) making sure `willPerformBatchUpdatesWithCollectionView` is only called when performing a batch update. [Maxime Ollivier](https://github.com/maxolls) (tbd)
 
 - Fixed missing update when calling `performUpdatesAnimated` multiple times quickly and using the `reloadDataFallback()`. [Maxime Ollivier](https://github.com/maxolls) (tbd)

Source/IGListDiffKit/IGListExperiments.h

@@ -20,10 +20,8 @@ typedef NS_OPTIONS (NSInteger, IGListExperiment) {
     IGListExperimentBackgroundDiffing = 1 << 2,
     /// Test invalidating layout when cell reloads/updates in IGListBindingSectionController.
     IGListExperimentInvalidateLayoutForUpdates = 1 << 3,
-    /// Test removing the layout before performing an update
-    IGListExperimentSkipLayoutBeforeUpdate = 1 << 4,
     /// Test array and set optimization on update
-    IGListExperimentArrayAndSetOptimization = 1 << 5,
+    IGListExperimentArrayAndSetOptimization = 1 << 4,
 };
 
 /**

Source/IGListKit/IGListAdapterUpdater.m

@@ -275,10 +275,6 @@ - (void)performBatchUpdatesWithCollectionViewBlock:(IGListCollectionViewBlock)co
 
     // block that executes the batch update and exception handling
     void (^tryToPerformUpdate)(IGListIndexSetResult *) = ^(IGListIndexSetResult *result){
-        if (!IGListExperimentEnabled(experiments, IGListExperimentSkipLayoutBeforeUpdate)) {
-            [collectionView layoutIfNeeded];
-        }
-
         @try {
             if (collectionView.dataSource == nil) {
                 // If the data source is nil, we should not call any collection view update.

Tests/IGListAdapterUpdaterTests.m

@@ -773,8 +773,6 @@ - (void)test_whenPerformIndexPathUpdates_reloadingTheSameIndexPathMultipleTimes_
 }
 
 - (void)test_whenPerformingUpdatesMultipleTimesInARow_thenUpdateWorks {
-    self.updater.experiments |= IGListExperimentSkipLayoutBeforeUpdate;
-
     NSArray *objects1 = @[
         [IGSectionObject sectionWithObjects:@[@0]]
     ];