Test fixing double insert crash

Summary: Looking at crash logs, the new high-firing crash has 2 item inserts in it. Test deduping the insert. Testing b/c I want to make sure there aren't any weird side effects.

Differential Revision: D6605474

fbshipit-source-id: 522120074aed2ed4995104443d48d8254ddb4fec

CHANGELOG.md

@@ -35,6 +35,8 @@ The changelog for `IGListKit`. Also see the [releases](https://github.com/instag
 
 - Check object type on lookup to prevent crossing types if different objects collide with their identifiers. [Ryan Nystrom](https://github.com/rnystrom) [(#tbd)](https://github.com/Instagram/IGListKit/pull/tbd)
 
+- Testing a fix that removes duplicate item-level updates. [Ryan Nystrom](https://github.com/rnystrom) (tbd)
+
 3.1.1
 -----
 

Source/Common/IGListExperiments.h

@@ -24,6 +24,8 @@ typedef NS_OPTIONS (NSInteger, IGListExperiment) {
     IGListExperimentReloadDataFallback = 1 << 3,
     /// Test a faster way to return visible section controllers.
     IGListExperimentFasterVisibleSectionController = 1 << 4,
+    /// Test deduping item-level updates.
+    IGListExperimentDedupeItemUpdates = 1 << 5,
 };
 
 /**

Source/IGListAdapterUpdater.m

@@ -309,6 +309,11 @@ void convertReloadToDeleteInsert(NSMutableIndexSet *reloads,
     [itemDeletes addObjectsFromArray:[reloadDeletePaths allObjects]];
     [itemInserts addObjectsFromArray:[reloadInsertPaths allObjects]];
 
+    if (IGListExperimentEnabled(self.experiments, IGListExperimentDedupeItemUpdates)) {
+        itemDeletes = [[[NSSet setWithArray:itemDeletes] allObjects] mutableCopy];
+        itemInserts = [[[NSSet setWithArray:itemInserts] allObjects] mutableCopy];
+    }
+
     IGListBatchUpdateData *updateData = [[IGListBatchUpdateData alloc] initWithInsertSections:inserts
                                                                                deleteSections:deletes
                                                                                  moveSections:moves

Tests/IGListAdapterE2ETests.m

@@ -1786,4 +1786,23 @@
     [self waitForExpectationsWithTimeout:30 handler:nil];
 }
 
+- (void)test_whenInsertingItemTwice_withDedupeExperiment_thatSecondInsertGetsDropped {
+    ((IGListAdapterUpdater*)self.updater).experiments = IGListExperimentDedupeItemUpdates;
+
+    IGTestObject *object = genTestObject(@1, @1);
+    [self setupWithObjects:@[object]];
+
+    IGTestDelegateController *controller = [self.adapter sectionControllerForObject:self.dataSource.objects.firstObject];
+    XCTestExpectation *expectation = genExpectation;
+    [controller.collectionContext performBatchAnimated:YES updates:^(id<IGListBatchContext>  _Nonnull batchContext) {
+        object.value = @2;
+        [batchContext insertInSectionController:controller atIndexes:[NSIndexSet indexSetWithIndex:0]];
+        [batchContext insertInSectionController:controller atIndexes:[NSIndexSet indexSetWithIndex:0]];
+    } completion:^(BOOL finished) {
+        [expectation fulfill];
+    }];
+
+    [self waitForExpectationsWithTimeout:30 handler:nil];
+}
+
 @end