From 039e77e3593251c8711497f76ab25857d641ecee Mon Sep 17 00:00:00 2001
From: Zhisheng Huang <zsh@fb.com>
Date: Mon, 29 Oct 2018 18:32:21 -0700
Subject: [PATCH] Add diffResult as argument to pass to willCrashWithException:
 in IGListAdapterUpdaterDelegate

Summary: This would help us understands what was the diff result from the algorithm and compare it with the `updates` to check what went wrong. Essentially, this would make our debugging easier going forward.

Reviewed By: calimarkus

Differential Revision: D12828892

fbshipit-source-id: 6dc52cdba1adb5a841760b51599e2df4c845c364
---
 CHANGELOG.md                          | 2 ++
 Source/IGListAdapterUpdater.m         | 1 +
 Source/IGListAdapterUpdaterDelegate.h | 2 ++
 3 files changed, 5 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 454a95e63..7b339c5b0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,8 @@ The changelog for `IGListKit`. Also see the [releases](https://github.com/instag
 
 - Renamed `[IGListAdapterUpdatingDelegate listAdapterUpdater:willPerformBatchUpdatesWithCollectionView:]` to `[IGListAdapterUpdatingDelegate listAdapterUpdater:willPerformBatchUpdatesWithCollectionView:fromObjects:toObjects:listIndexSetResult:]` to include more supporting info on updated objects. [Jeremy Cohen] (https://github.com/jeremycohen) (tbd)
 
+- Renamed `[IGListAdapterUpdatingDelegatelistAdapterUpdater:collectionView:willCrashWithException:fromObjects:toObjects:updates:]` to `[ IGListAdapterUpdatingDelegatelistAdapterUpdater:collectionView:willCrashWithException:fromObjects:toObjects:diffResult:updates:]` to include diff result info. [Zhisheng Huang] (https://github.com/lorixx) (tbd)
+
 ### Enhancements
 
 - Added `IGListCollectionScrollingTraits` for exposing `UICollectionView` scrolling traits to section controllers via `IGListCollectionContext`. [Adam Stern](https://github.com/adamastern) (tbd)
diff --git a/Source/IGListAdapterUpdater.m b/Source/IGListAdapterUpdater.m
index 31a207063..98edfe44f 100644
--- a/Source/IGListAdapterUpdater.m
+++ b/Source/IGListAdapterUpdater.m
@@ -255,6 +255,7 @@ - (void)performBatchUpdatesWithCollectionViewBlock:(IGListCollectionViewBlock)co
                   willCrashWithException:exception
                              fromObjects:fromObjects
                                toObjects:toObjects
+                              diffResult:result
                                  updates:(id)self.applyingUpdateData];
             @throw exception;
         }
diff --git a/Source/IGListAdapterUpdaterDelegate.h b/Source/IGListAdapterUpdaterDelegate.h
index 1d8059d89..0200faf83 100644
--- a/Source/IGListAdapterUpdaterDelegate.h
+++ b/Source/IGListAdapterUpdaterDelegate.h
@@ -141,6 +141,7 @@ willPerformBatchUpdatesWithCollectionView:(UICollectionView *)collectionView
  @param exception The exception thrown by the collection view.
  @param fromObjects The items transitioned from in the diff, if any.
  @param toObjects The items transitioned to in the diff, if any.
+ @param diffResult The diff result that were computed from `fromObjects` and `toObjects`.
  @param updates The batch updates that were applied to the collection view.
  */
 - (void)listAdapterUpdater:(IGListAdapterUpdater *)listAdapterUpdater
@@ -148,6 +149,7 @@ willPerformBatchUpdatesWithCollectionView:(UICollectionView *)collectionView
     willCrashWithException:(NSException *)exception
                fromObjects:(nullable NSArray *)fromObjects
                  toObjects:(nullable NSArray *)toObjects
+                diffResult:(IGListIndexSetResult *)diffResult
                    updates:(IGListBatchUpdateData *)updates;
 
 @end