Rails 5 polymorphic associations not saving

[petermumford]

Hello. I am trying to create a polymorphic association with a has_many :through for categories.

Steps to reproduce

I have created two very simple repositories one with Rails 5.0.0.beta3 and the other using Rails 4.1.13, which works as expected.

Expected behavior

When you create an event with multiple categories selected it should create the association between the event and category on the categorisations model.

Actual behavior

However, when saving the event with multiple categories selected I get the following error: @messages={:categorisations=>["is invalid"]} when using Rails 5.0.0.beta3

Below is the output when debugging from byebug:

(byebug) event_params <ActionController::Parameters {"name"=>"Test", "location"=>"london", "category_ids"=>["", "1", "2"]} permitted: true>

`(byebug) @event

<Event id: nil, name: "Test", location: "london", created_at: nil, updated_at: nil>`

`(byebug) @event.categorisations

<ActiveRecord::Associations::CollectionProxy [#<Categorisation id: nil, category_id: 1, categorisable_type: "Event", categorisable_id: nil, created_at: nil, updated_at: nil>, #<Categorisation id: nil, category_id: 2, categorisable_type: "Event", categorisable_id: nil, created_at: nil, updated_at: nil>]>`

`(byebug) @event.categories

<ActiveRecord::Associations::CollectionProxy [#<Category id: 1, name: "Category 1", created_at: "2016-02-28 21:51:16", updated_at: "2016-02-28 21:51:16">, #<Category id: 2, name: "Category 2", created_at: "2016-02-28 21:51:24", updated_at: "2016-02-28 21:51:24">]>`

(byebug) @event.valid? false

`(byebug) @event.errors

<ActiveModel::Errors:0x007fa113eda628 @base=#<Event id: nil, name: "Test", location: "london", created_at: nil, updated_at: nil>, @messages={:categorisations=>["is invalid"]}, @details={:categorisations=>[{:error=>:invalid}, {:error=>:invalid}]}>`

System configuration

Rails version: 5.0.0.beta3
Ruby version: 2.2.3

[eileencodes]

Hi @petermumford, thanks for the report! In Rails 5 belongs_to is required by default so if you add optional: true to your belongs to does the test pass? Technically this is correct behavior because the record is not valid because it's required by default. There was a change I made to validations where this would have been returning valid? as true but that was incorrect behavior and I reverted it between beta2 and beta3 .

I believe this is the same issue as here; #23911

[petermumford]

Thank you @eileencodes. I've added optional to my belongs_to association and now it works. So my model looks like this:

class Categorisation < ApplicationRecord
belongs_to :category
belongs_to :categorisable, polymorphic: true, optional: true
end

I tried adding optional to belongs_to :category but it still failed. It only works on the polymorphic association. Is that where you meant?

What is the correct way of doing this now then, is it like the above from 5.0.0.beta3? Do you have this documented anywhere, appreciate this is still new but thought I'd ask just in case.

[eileencodes]

Yup @petermumford that's the correct way. I'm going to update the documentation. Sorry for the confusion!

To get the old Rails 4.1 behavior you can change this line to false in your app. https://github.com/petermumford/testpoly5/blob/master/config/initializers/active_record_belongs_to_required_by_default.rb#L6

The reason you're seeing the error on categorizations and not category is because your category isn't nil, but your categorizations are. So when you ask if it's valid? it's false.

[eileencodes]

I closed because there's another open issue to fix the documentation so we don't need two 😄

[petermumford]

That's great. Fully understand, thank you.

[acrolink]

Thank you very much @eileencodes

[JarLowrey]

So I'm trying to create a has_one address, as: :addressable (in Event) but am running into issues. I believe it is because the event/address is not created yet in the nested form, and causes a validation issue. Adding optional: true to Address allows the form to save, but then what's the point of the optional? This relationship is not optional, every event should have an address, but that seems to be the only way I can get this new behavior to work.

Figured it out, solution in #29781