Fix crash during CollectionView thrash

Signal/src/ViewControllers/ConversationView/ConversationViewController.m

@@ -3402,20 +3402,20 @@ typedef enum : NSUInteger {
         for (YapDatabaseViewRowChange *rowChange in rowChanges) {
             switch (rowChange.type) {
                 case YapDatabaseViewChangeDelete: {
-                    DDLogVerbose(@"YapDatabaseViewChangeDelete: %@, %@, %zd",
+                    DDLogVerbose(@"YapDatabaseViewChangeDelete collectionKey: %@, indexPath: %@, finalIndex: %lu",
                         rowChange.collectionKey,
                         rowChange.indexPath,
-                        rowChange.finalIndex);
+                        (unsigned long)rowChange.finalIndex);
                     [self.collectionView deleteItemsAtIndexPaths:@[ rowChange.indexPath ]];
                     YapCollectionKey *collectionKey = rowChange.collectionKey;
                     OWSAssert(collectionKey.key.length > 0);
                     break;
                 }
                 case YapDatabaseViewChangeInsert: {
-                    DDLogVerbose(@"YapDatabaseViewChangeInsert: %@, %@, %zd",
+                    DDLogVerbose(@"YapDatabaseViewChangeInsert collectionKey: %@, newIndexPath: %@, finalIndex: %lu",
                         rowChange.collectionKey,
                         rowChange.newIndexPath,
-                        rowChange.finalIndex);
+                        (unsigned long)rowChange.finalIndex);
                     [self.collectionView insertItemsAtIndexPaths:@[ rowChange.newIndexPath ]];
 
                     ConversationViewItem *_Nullable viewItem = [self viewItemForIndex:(NSInteger)rowChange.finalIndex];
@@ -3429,19 +3429,20 @@ typedef enum : NSUInteger {
                     break;
                 }
                 case YapDatabaseViewChangeMove: {
-                    DDLogVerbose(@"YapDatabaseViewChangeMove: %@, %@, %@, %zd",
+                    DDLogVerbose(@"YapDatabaseViewChangeMove collectionKey: %@, indexPath: %@, newIndexPath: %@, "
+                                 @"finalIndex: %lu",
                         rowChange.collectionKey,
                         rowChange.indexPath,
                         rowChange.newIndexPath,
-                        rowChange.finalIndex);
+                        (unsigned long)rowChange.finalIndex);
                     [self.collectionView moveItemAtIndexPath:rowChange.indexPath toIndexPath:rowChange.newIndexPath];
                     break;
                 }
                 case YapDatabaseViewChangeUpdate: {
-                    DDLogVerbose(@"YapDatabaseViewChangeUpdate: %@, %@, %zd",
+                    DDLogVerbose(@"YapDatabaseViewChangeUpdate collectionKey: %@, indexPath: %@, finalIndex: %lu",
                         rowChange.collectionKey,
                         rowChange.indexPath,
-                        rowChange.finalIndex);
+                        (unsigned long)rowChange.finalIndex);
                     [self.collectionView reloadItemsAtIndexPaths:@[ rowChange.indexPath ]];
                     break;
                 }
@@ -3466,16 +3467,31 @@ typedef enum : NSUInteger {
             [self scrollToBottomAnimated:shouldAnimateScrollToBottom];
         }
     };
+
     if (shouldAnimateUpdates) {
         [self.collectionView performBatchUpdates:batchUpdates completion:batchUpdatesCompletion];
     } else {
-        [UIView performWithoutAnimation:^{
+        // HACK: We use `UIView.animateWithDuration:0` rather than `UIView.performWithAnimation` to work around a UIKit
+        // Crash like:
+        //
+        //     *** Assertion failure in -[ConversationViewLayout prepareForCollectionViewUpdates:],
+        //     /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit_Sim/UIKit-3600.7.47/UICollectionViewLayout.m:760
+        //     *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'While
+        //     preparing update a visible view at <NSIndexPath: 0xc000000011c00016> {length = 2, path = 0 - 142} wasn't
+        //     found in the current data model and was not in an update animation. This is an internal error.'
+        //
+        // I'm unclear if this is a bug in UIKit, or if we're doing something crazy in
+        // ConversationViewLayout#prepareLayout. To reproduce, rapidily insert and delete items into the conversation.
+        // See `DebugUIMessages#thrashCellsInThread:`
+        [UIView animateWithDuration:0.0
+                         animations:^{
                              [self.collectionView performBatchUpdates:batchUpdates completion:batchUpdatesCompletion];
                              if (scrollToBottom) {
-                [self scrollToBottomAnimated:NO];
+                                 [self scrollToBottomAnimated:shouldAnimateUpdates];
                              }
                          }];
     }
+
     self.lastReloadDate = [NSDate new];
 }
 

Signal/src/ViewControllers/DebugUI/DebugUIMessages.m

@@ -85,10 +85,12 @@ NS_ASSUME_NONNULL_BEGIN
                                      actionBlock:^{
                                          [DebugUIMessages deleteAllMessagesInThread:thread];
                                      }]];
-    [items addObject:[OWSTableItem itemWithTitle:@"👷 Send All Contact Shares"
+    [items addObject:[OWSTableItem itemWithTitle:@"👷 Thrash insert/deletes"
                                      actionBlock:^{
-                                         [DebugUIMessages sendAllContacts:thread];
+                                         [DebugUIMessages thrashInsertAndDeleteForThread:(TSThread *)thread
+                                                                                 counter:300];
                                      }]];
+
     [items addObjectsFromArray:[self itemsForActions:@[
         [DebugUIMessages fakeAllContactShareAction:thread],
         [DebugUIMessages sendMessageVariationsAction:thread],
@@ -126,6 +128,10 @@ NS_ASSUME_NONNULL_BEGIN
                         actionBlock:^{
                             [DebugUIMessages selectSendMediaAction:thread];
                         }],
+        [OWSTableItem itemWithTitle:@"Send All Contact Shares"
+                        actionBlock:^{
+                            [DebugUIMessages sendAllContacts:thread];
+                        }],
         [OWSTableItem itemWithTitle:@"Select Quoted Reply"
                         actionBlock:^{
                             [DebugUIMessages selectQuotedReplyAction:thread];
@@ -3111,7 +3117,7 @@ typedef OWSContact * (^OWSContactBlock)(YapDatabaseReadWriteTransaction *transac
     OWSAssert(thread);
 
     return
-        [DebugUIMessagesGroupAction allGroupActionWithLabel:@"👷 All Fake Contact Shares"
+        [DebugUIMessagesGroupAction allGroupActionWithLabel:@"All Fake Contact Shares"
                                                  subactions:[self allFakeContactShareActions:thread includeLabels:YES]];
 }
 
@@ -3700,6 +3706,26 @@ typedef OWSContact * (^OWSContactBlock)(YapDatabaseReadWriteTransaction *transac
     }
 }
 
++ (void)thrashInsertAndDeleteForThread:(TSThread *)thread counter:(NSUInteger)counter
+{
+    if (counter == 0) {
+        return;
+    }
+    uint32_t sendDelay = arc4random_uniform((uint32_t)(0.01 * NSEC_PER_SEC));
+    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, sendDelay), dispatch_get_main_queue(), ^{
+        [self sendFakeMessages:1 thread:thread];
+    });
+
+    uint32_t deleteDelay = arc4random_uniform((uint32_t)(0.01 * NSEC_PER_SEC));
+    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, deleteDelay), dispatch_get_main_queue(), ^{
+        [OWSPrimaryStorage.sharedManager.dbReadWriteConnection
+            asyncReadWriteWithBlock:^(YapDatabaseReadWriteTransaction *_Nonnull transaction) {
+                [self deleteRandomMessages:1 thread:thread transaction:transaction];
+            }];
+        [self thrashInsertAndDeleteForThread:thread counter:counter - 1];
+    });
+}
+
 // TODO: Remove.
 + (void)sendFakeMessages:(NSUInteger)counter
                   thread:(TSThread *)thread