add assert for iOS 18 cell dequeue exceptions

Summary:
iOS 18 has new exceptions, which can be a bit tough to debug. The common ones we see:
1. Cell dequeue outside of -cellForIndex
2. Dequeue being called more than once
3. Returning a cell that was not dequeued

Lets add an assert for each. #1 and #2 can actually assert on the problematic call, which will give a nice stack strace. #3 will still have a generic stack trace, but at least we'll see the section-controller.

Differential Revision: D62809660

fbshipit-source-id: 454c44598d4b21e09e6f66eb63c502b1b966a993

Source/IGListDiffKit/IGListAssert.h

@@ -33,3 +33,11 @@
 #ifndef IGAssertMainThread
 #define IGAssertMainThread() IGAssert( ([NSThread isMainThread] == YES), @"Must be on the main thread")
 #endif // IGAssertMainThread
+
+#ifndef IG_ASSERTIONS_ENABLED
+ #if !defined(NS_BLOCK_ASSERTIONS)
+  #define IG_ASSERTIONS_ENABLED 1
+ #else
+  #define IG_ASSERTIONS_ENABLED 0
+ #endif
+#endif

Source/IGListKit/IGListAdapter.m

@@ -1154,7 +1154,7 @@ - (__kindof UICollectionViewCell *)dequeueReusableCellOfClass:(Class)cellClass
         [self.registeredCellIdentifiers addObject:identifier];
         [collectionView registerClass:cellClass forCellWithReuseIdentifier:identifier];
     }
-    return [collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];
+    return [self _dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath forSectionController:sectionController];
 }
 
 - (__kindof UICollectionViewCell *)dequeueReusableCellOfClass:(Class)cellClass
@@ -1172,7 +1172,7 @@ - (__kindof UICollectionViewCell *)dequeueReusableCellFromStoryboardWithIdentifi
     UICollectionView *collectionView = self.collectionView;
     IGAssert(collectionView != nil, @"Reloading adapter without a collection view.");
     NSIndexPath *indexPath = [self indexPathForSectionController:sectionController index:index usePreviousIfInUpdateBlock:NO];
-    return [collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];
+    return [self _dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath forSectionController:sectionController];
 }
 
 - (UICollectionViewCell *)dequeueReusableCellWithNibName:(NSString *)nibName
@@ -1191,7 +1191,19 @@ - (UICollectionViewCell *)dequeueReusableCellWithNibName:(NSString *)nibName
         UINib *nib = [UINib nibWithNibName:nibName bundle:bundle];
         [collectionView registerNib:nib forCellWithReuseIdentifier:nibName];
     }
-    return [collectionView dequeueReusableCellWithReuseIdentifier:nibName forIndexPath:indexPath];
+    return [self _dequeueReusableCellWithReuseIdentifier:nibName forIndexPath:indexPath forSectionController:sectionController];
+}
+
+- (UICollectionViewCell *)_dequeueReusableCellWithReuseIdentifier:(NSString *)identifier forIndexPath:(NSIndexPath *)indexPath forSectionController:(IGListSectionController *)sectionController {
+    // These will cause a crash in iOS 18
+    IGAssert(_dequeuedCells.count == 0, @"Dequeueing more than one cell (%@) for indexPath %@, section controller %@,", identifier, indexPath, sectionController);
+    IGAssert(_isDequeuingCell, @"Dequeueing a cell (%@) without a request from the UICollectionView for indexPath %@, section controller %@", identifier, indexPath, sectionController);
+
+    UICollectionViewCell *const cell = [self.collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];
+    if (_isDequeuingCell && cell) {
+        [_dequeuedCells addObject:cell];
+    }
+    return cell;
 }
 
 - (__kindof UICollectionReusableView *)dequeueReusableSupplementaryViewOfKind:(NSString *)elementKind

Source/IGListKit/Internal/IGListAdapter+UICollectionView.m

@@ -44,6 +44,12 @@ - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cell
 
     IGListSectionController *sectionController = [self sectionControllerForSection:indexPath.section];
 
+#if IG_ASSERTIONS_ENABLED
+    if (!_dequeuedCells) {
+        _dequeuedCells = [NSMutableSet new];
+    }
+#endif
+
     // flag that a cell is being dequeued in case it tries to access a cell in the process
     _isDequeuingCell = YES;
     UICollectionViewCell *cell = [sectionController cellForItemAtIndex:indexPath.item];
@@ -52,8 +58,15 @@ - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cell
     IGAssert(cell != nil, @"Returned a nil cell at indexPath <%@> from section controller: <%@>", indexPath, sectionController);
     if (cell) {
         IGAssert(cell.reuseIdentifier != nil, @"Returned a cell without a reuseIdentifier at indexPath <%@> from section controller: <%@>", indexPath, sectionController);
+
+        if (_dequeuedCells) {
+            // This will cause a crash in iOS 18
+            IGAssert([_dequeuedCells containsObject:cell], @"Returned a cell (%@) that was not dequeued at indexPath %@ from section controller %@", NSStringFromClass([cell class]), indexPath, sectionController);
+        }
     }
 
+    [_dequeuedCells removeAllObjects];
+
     // associate the section controller with the cell so that we know which section controller is using it
     [self mapView:cell toSectionController:sectionController];
 

Source/IGListKit/Internal/IGListAdapterInternal.h

@@ -29,7 +29,10 @@ IGListBatchContext
 >
 {
     __weak UICollectionView *_collectionView;
+
     BOOL _isDequeuingCell;
+    NSMutableSet<UICollectionViewCell *> *_dequeuedCells;
+
     BOOL _isDequeuingSupplementaryView;
 
     BOOL _isSendingWorkingRangeDisplayUpdates;