Unexpected behaviour when inserting consecutive items with default positions

[jonasschneider]

Environment: Suppose Item has acts_as_list and a position column with default of 0.

1. Insert an item A into the list. (a = Item.create!)
2. Insert another item B into the list. (b = Item.create!)

Expected behaviour: a.position == 1, b.position == 2

Actual behaviour: a.position == 2, b.position == 1.

I believe the culprit is 3ebaffc. The setting of the top position there is causing the check in add_to_list_bottom at https://github.com/swanandp/acts_as_list/blob/3ebaffc2680a7ba4ca5bef175e35ab0207e28562/lib/acts_as_list/active_record/acts/list.rb#L290 to take the wrong branch, and reverse the positions on the items.

Am I missing something here, or is this a bug?

[jonasschneider]

Also: this works as expected in 0.3.0, but is broken as described in 0.4.0.

[swanandp]

Thanks for reporting. Does look like a side effect of 3ebaffc. Can you add a failing test case and send a PR?

[brendon]

I thought I had this reproduced, but I couldn't reproduce it. I'm going to close this for now unless someone can provide a test case that shows the bug.