IGListBindingSectionController no longer asserts when reloading the e…

…ntire section. (Instagram#1213)

Summary:
Issue fixed: Instagram#1174

- [X] All tests pass. Demo project builds and runs.
- [x] I added tests, an experiment, or detailed why my change isn't tested.
- [X] I added an entry to the `CHANGELOG.md` for any breaking changes, enhancements, or bug fixes.
- [X] I have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/.github/CONTRIBUTING.md)
Pull Request resolved: Instagram#1213

Differential Revision: D9003398

Pulled By: rnystrom

fbshipit-source-id: 2c68f42e21abaea9191f26309668d866544f80b4

CHANGELOG.md

@@ -4,6 +4,27 @@ The changelog for `IGListKit`. Also see the [releases](https://github.com/instag
 
 4.0.0 (upcoming release)
 -----
+### Breaking Changes
+
+- All `IGListBindingSectionControllerSelectionDelegate` methods are now required. [Bofei Zhu] (https://github.com/zhubofei) [(#1186)](https://github.com/Instagram/IGListKit/pull/1186)
+
+### Enhancements
+
+- Added `IGListCollectionScrollingTraits` for exposing `UICollectionView` scrolling traits to section controllers via `IGListCollectionContext`. [Adam Stern](https://github.com/adamastern) (tbd)
+
+-  `IGListBindingSectionController` no longer asserts when reloading the entire section. A warning message is now logged if the entire section is going to be reloaded. [Jeff Bailey](https://github.com/jeffbailey) (#1213)
+
+### Fixes
+
+- Experimental fix to get the `UICollectionView` for batch updating immediately before applying the update. [Ryan Nystrom](https://github.com/rnystrom) (tbd)
+
+- `[IGListAdapterUpdater performBatchUpdatesWithCollectionViewBlock:]` and `[IGListAdapterUpdater performReloadDataWithCollectionViewBlock:]` clean state and run completion blocks if their `UICollectionView` is nil. [Brandon Darin](https://github.com/jbd1030) (tbd)
+
+- Ensuring view models with duplicate diff identifiers are removed when view models are first requested by `IGListBindingSectionController` [Adam Stern](https://github.com/adamastern) (tbd)
+
+- Fixed `[IGListAdapterUpdater reloadItemInCollectionView:fromIndexPath:toIndexPath:]` does not call delegate when not inside a batch update. [Bofei Zhu] (https://github.com/zhubofei) [(#1211)](https://github.com/Instagram/IGListKit/pull/1211)
+
+- Log instead of assert for duplicate diff identifiers to make code testable. [Adam Stern](https://github.com/adamastern) (tbd)
 
 3.4.0
 -----

Source/IGListBindingSectionController.m

@@ -114,9 +114,12 @@ - (void)didUpdateToObject:(id)object {
     if (oldObject == nil) {
         self.viewModels = [[self.dataSource sectionController:self viewModelsForObject:object] copy];
     } else {
-        IGAssert([oldObject isEqualToDiffableObject:object],
-                 @"Unequal objects %@ and %@ will cause IGListBindingSectionController to reload the entire section",
-                 oldObject, object);
+#if IGLK_LOGGING_ENABLED
+        if (![oldObject isEqualToDiffableObject:object]) {
+            IGLKLog(@"Warning: Unequal objects %@ and %@ will cause IGListBindingSectionController to reload the entire section",
+                    oldObject, object);
+        }
+#endif
         [self updateAnimated:YES completion:nil];
     }
 }

Tests/Objects/IGTestDiffingObject.m

@@ -28,8 +28,18 @@ - (NSString *)description {
     return self.key;
 }
 
-- (BOOL)isEqualToDiffableObject:(id<IGListDiffable>)object {
-    return YES;
+- (BOOL)isEqualToDiffableObject:(id)object {
+    if (object == self) {
+        return YES;
+    }
+    if ([object isKindOfClass:[IGTestDiffingObject class]]) {
+        /* A simple equality test that only looks at the number of objects for the key.
+           It does not currently test the equality of each of the objects. */
+        IGTestDiffingObject *testDiffingObject = (IGTestDiffingObject *)object;
+        return self.objects.count == testDiffingObject.objects.count;
+    }
+
+    return NO;
 }
 
 @end