Fix inconsistent state which can be caused in UICollectionViewLayout+…

…InteractiveReordering.

CHANGELOG.md

@@ -76,6 +76,8 @@ The changelog for `IGListKit`. Also see the [releases](https://github.com/instag
 
 - Fixed binding section controllers failing to update their cells when the section controller's section changes. [Chrisna Aing](https://github.com/ccrazy88) [(#1144)](https://github.com/Instagram/IGListKit/pull/1144)
 
+- Fixed a bug caused when applying interactive reordering on a single section item while dragging it through the last spot of the collection view and back to some (non-last) target position. [Ofir Gluzman](https://github.com/ofirgluzman) [#1289](https://github.com/Instagram/IGListKit/pull/1289)
+
 3.2.0
 -----
 

Source/Internal/UICollectionViewLayout+InteractiveReordering.m

@@ -104,6 +104,8 @@ - (nullable NSIndexPath *)updatedTargetForInteractivelyMovingItem:(NSIndexPath *
  if (destinationSectionIndex < [[adapter objects] count] - 1) {
  destinationSectionIndex += 1;
  destinationItemIndex = 0;
+
+ adapter.isLastInteractiveMoveToLastSectionIndex = NO;
  }
  else {
  // if we're moving an item to the last spot, our index would exceed the number of sections available
@@ -114,6 +116,12 @@ - (nullable NSIndexPath *)updatedTargetForInteractivelyMovingItem:(NSIndexPath *
  inSection:destinationSectionIndex];
  return updatedTarget;
  }
+ else {
+ adapter.isLastInteractiveMoveToLastSectionIndex = NO;
+ }
+ }
+ else {
+ adapter.isLastInteractiveMoveToLastSectionIndex = NO;
  }
 
  return nil;

Tests/IGListAdapterTests.m

@@ -1699,4 +1699,34 @@ - (void)test_whenItemsAreInteractivelyReorderedAcrossSections_thatIndexesRevertT
  XCTAssertEqual(section1Objects[2], section1.sectionObject.objects[2]);
 }
 
+- (void)test_whenSingleItemInSectionIsInteractivelyReorderedThorughLastSpot_indexesUpdateCorrectly {
+ IGListTestAdapterReorderingDataSource *dataSource = [IGListTestAdapterReorderingDataSource new];
+ dataSource.objects = @[@0, @1, @2];
+ self.adapter.dataSource = dataSource;
+ self.adapter.moveDelegate = dataSource;
+
+ IGTestReorderableSection *section0 = (IGTestReorderableSection *)[self.adapter sectionControllerForSection:0];
+ IGTestReorderableSection *section1 = (IGTestReorderableSection *)[self.adapter sectionControllerForSection:1];
+ IGTestReorderableSection *section2 = (IGTestReorderableSection *)[self.adapter sectionControllerForSection:2];
+ section0.sectionObject = [IGTestReorderableSectionObject sectionWithObjects:@[@0]];
+ section0.isReorderable = YES;
+ section1.sectionObject = [IGTestReorderableSectionObject sectionWithObjects:@[@0]];
+ section2.sectionObject = [IGTestReorderableSectionObject sectionWithObjects:@[@0]];
+
+ [self.adapter performUpdatesAnimated:NO completion:nil];
+
+ NSIndexPath *fromIndexPath = [NSIndexPath indexPathForItem:0 inSection:0];
+ NSIndexPath *lastSpotIndexPath = [NSIndexPath indexPathForItem:1 inSection:2];
+ NSIndexPath *toIndexPath = [NSIndexPath indexPathForItem:1 inSection:1];
+
+ // move the first section item to the middle while simulating dragging to the last spot and back.
+ NSIndexPath *interpretedPath = [self interpretedIndexPathFromIndexPath:fromIndexPath toIndexPath:lastSpotIndexPath];
+ interpretedPath = [self interpretedIndexPathFromIndexPath:interpretedPath toIndexPath:toIndexPath];
+ [self.adapter collectionView:self.collectionView moveItemAtIndexPath:fromIndexPath toIndexPath:interpretedPath];
+
+ XCTAssertEqual(section0, [self.adapter sectionControllerForSection:1]);
+ XCTAssertEqual(section1, [self.adapter sectionControllerForSection:0]);
+ XCTAssertEqual(section2, [self.adapter sectionControllerForSection:2]);
+}
+
 @end