has_many: use soft-delete when clearing associated collection about discard

[kowal]

@ivanbrennan I think now you can do big.littles.discard_all, which is way more explicit what is going on. Also, I think that sometimes you would actually want to just null out associations rather than discarding them.

[jarednorman]

Thanks for your clarification @kowal.

@ivanbrennan If you're looking for a gem that does soft deletion by overriding ActiveRecord behaviour, you might like paranoia.

I may make this more clear in the project's README or issue/pr templates, but discard does not and will not ever override the behaviour of ActiveRecord methods. That's the main thing that distinguishes it from paranoia.

[jarednorman]

big.littles = [] doesn't normally delete records, so it doesn't make sense for it to discard records either. We're going to leave it as is and keep the existing Rails behaviour the same, as changing this would be pretty unexpected.

[ivanbrennan]

big.littles = [] doesn't normally delete records

@jarednorman That has not been my experience, and the has_many documentation seem to confirm the delete behavior:

collection=objects
Replaces the collections content by deleting and adding objects as appropriate.

@kowal Using discard_all would make sense if I was unconditionally discarding, but the use-case that brought this up for me was handling an update that modifies the associated collection, adding some new records, potentially modifying some existing ones, and potentially removing some existing ones.

[kowal]

@ivanbrennan @jarednorman
OK, It's not so simple. From what I checked, having has_many association without any options does not destroy/delete associated records when calling big.littles = []. But this indeed happens when I specify dependent: :destroy option.

So, since big.littles = [] does not have single semantic and it depends on association config, maybe it is better not to override it with discard function.

[ivanbrennan]

@kowal @jarednorman Thank you both for the clarifications. Indeed, in my actual use-case I was using dependent: :destroy. (I should have included that in my example, apologies.)