Gate the preferItemReloadsForSectionReloads only to use when there is…

… no change to the number of sections Summary: There are some crashes related to this path when the number of sections are changed when using the `preferItemReloadsForSectionReloads` optimization for item reloads. For now, this change would just limit the flag only useable when the section count is unchanged. The proper fix would be finding a repro-case for the unsafe trace. The follow-up here is adding more logging to capture the crash reason and investigate any variable that leads to this crash. Reviewed By: calimarkus Differential Revision: D12828061 fbshipit-source-id: 040e66c051c54f889ee9fbc3e4a48ab6bf93e162
Instagram · Oct 29, 2018 · c1bf5f1 · c1bf5f1
1 parent 0efb259
commit c1bf5f1
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Showing 2 changed files with 7 additions and 6 deletions.
diff --git a/Source/IGListAdapterUpdater.m b/Source/IGListAdapterUpdater.m
@@ -333,8 +333,9 @@ - (IGListBatchUpdateData *)_flushCollectionView:(UICollectionView *)collectionVi
         moves = [NSSet new];
     }
 
-    // Item reloads are not safe, if any section moves happened
-    if (moves.count == 0 && self.preferItemReloadsForSectionReloads) {
+    // Item reloads are not safe, if any section moves happened or there are inserts/deletes.
+    if (self.preferItemReloadsForSectionReloads
+        && moves.count == 0 && inserts.count == 0 && deletes.count == 0 && reloads.count > 0) {
         [reloads enumerateIndexesUsingBlock:^(NSUInteger sectionIndex, BOOL * _Nonnull stop) {
             NSMutableIndexSet *localIndexSet = [NSMutableIndexSet indexSetWithIndex:sectionIndex];
             if (sectionIndex < [collectionView numberOfSections]

diff --git a/Tests/IGListAdapterUpdaterTests.m b/Tests/IGListAdapterUpdaterTests.m
@@ -869,15 +869,15 @@ - (void)test_whenReloadIsCalledWithSectionMoveAndUpdate_withThreeSections_delete
     [mockDelegate verify];
 }
 
-- (void)test_whenReloadIsCalledWithSectionInsertAndUpdate_andPreferItemReload_orderHappened {
+- (void)test_whenReloadIsCalledWithSectionInsertAndUpdate_andPreferItemReload_noItemReloads {
     self.updater.preferItemReloadsForSectionReloads = YES;
 
-    IGListBatchUpdateData *expectedBatchUpdateData = [[IGListBatchUpdateData alloc] initWithInsertSections:[NSIndexSet indexSetWithIndex:1]
-                                                                                            deleteSections:[NSIndexSet new]
+    IGListBatchUpdateData *expectedBatchUpdateData = [[IGListBatchUpdateData alloc] initWithInsertSections:[NSIndexSet indexSetWithIndexesInRange:NSMakeRange(0, 2)]
+                                                                                            deleteSections:[NSIndexSet indexSetWithIndex:0]
                                                                                               moveSections:[NSSet new]
                                                                                           insertIndexPaths:@[]
                                                                                           deleteIndexPaths:@[]
-                                                                                          updateIndexPaths:@[[NSIndexPath indexPathForItem:0 inSection:0]]
+                                                                                          updateIndexPaths:@[]
                                                                                             moveIndexPaths:@[]];
     NSArray<IGSectionObject *> *from = @[[IGSectionObject sectionWithObjects:@[@1] identifier:@"id1"]];
     NSArray<IGSectionObject *> *to = @[[IGSectionObject sectionWithObjects:@[@2] identifier:@"id1"],