IGListBindingSectionController updateAnimated have copy BUG

[YasinZhou]

IGListBindingSectionController.m

• (void)updateAnimated:(BOOL)animated completion:(void (^)(BOOL))completion{}

oldViewModels = self.viewModels;

and late

self.viewModels = [self.dataSource sectionController:self viewModelsForObject:object];
result = IGListDiff(oldViewModels, self.viewModels, IGListDiffEquality);

if self.viewModels is a NSMutableArray and just removeAllObjects and change the all value,
result = IGListDiff(oldViewModels, self.viewModels, IGListDiffEquality); is NOT right
so i think , oldViewModels need copy the self.viewModels([self.viewModels copy]) or self.viewModels's property replaces strong with copy.

and i think another updateAnimated have same BUG maybe

[rnystrom]

Thanks for investigating @YasinZhou! We deduplicate the models returned from the data source, so even if a mutable array is returned, it should be totally safe.

You made me double check everything though, and I did come across this, and you're right that if the data source returns an NSMutableArray, they could mutate the array and corrupt the models stored inside the binding section controller.

That'd be a really easy and useful fix if you want to submit a PR!

[rnystrom]

Good bug, but not world-ending. Leaving as a great starter task for someone!

[KashishGoel]

@rnystrom I decided to take care of this. However, I'm not sure if this is something we need to write a test for. I don't think we need to write one for this change. Any thoughts on this?