Deletion of item in BootstrapCollectionType deletes wrong item.

[matejvelikonja]

I encountered an issue while deleting item from BootstrapCollectionType.
When you delete one of the items using forms, the last item is always deleted instead. I've already debugged a little bit a found out that the problem is in the ReorderCollectionSubscriber.
This subscribers resets keys of the array and that's why the last item is always deleted.

For example:
I have an array:

[
    0 => "zero",
    1 => "one",
    2 => "two",
]

By using forms I delete first array element and all I have now is:

[
    1 => "one",
    2 => "two",
]

When this array is passed to the ReorderCollectionSubscriber in changes array to:

[
    0 => "one",
    1 => "two",
]

And this array is at some point passed to doctrine, doctrine does the calculation and from the array it assumes that the array element with key 2 was deleted and so the last entry is deleted from the database.

Maybe I forgot to set something but I don't know why and I don't even know why this ReorderCollectionSubscriber is doing this at all.

In my opinion this is quite a serious bug and should be addresses as soon as possible. For the current project I just commented out the adding of ReorderCollectionSubscriber to BootstrapCollectionType and the problem is gone and as far as I see everything is working normally. But not sure if this is the proper solution.