Thanks for your quick response and fix! I think adding the default in
after_save should work just fine.
Happy to hear that the example helped fix the bug. Sequel has been a
pleasure to work with so I'm glad to be able to contribute in any way I can!
On Saturday, November 20, 2021 at 12:04:10 AM UTC-8 Jeremy Evans wrote:
> On Fri, Nov 19, 2021 at 7:26 PM s.brimd...@gmail.com <s.brimd...@gmail.com>
> wrote:
>
>> I'm having some trouble using nested_attributes in conjunction with the
>> tactical_eager_loading plugin.
>>
>> Specifically, I'm trying to set a default value for a one_to_one
>> association in before_validation only if that association doesn't already
>> have an associated object via an update of a one_to_many association also
>> using nested attributes. However, it seems that the association is always
>> cleared by the time we get to before_validation so we always end up with
>> the default.
>>
>> Here is a basic setup to illustrate the problem:
>>
>> DB.create_table :albums do
>> primary_key :id
>> column :title, :text
>> end
>>
>> DB.create_table :tracks do
>> primary_key :id
>> column :title, :text
>> foreign_key :album_id, :albums, null: false
>> end
>>
>> DB.create_table :studios do
>> primary_key :id
>> column :name, :text
>> foreign_key :track_id, :tracks
>> end
>>
>> Sequel::Model.plugin :nested_attributes
>> Sequel::Model.plugin :tactical_eager_loading
>>
>> class Album < Sequel::Model
>> one_to_many :tracks
>> nested_attributes :tracks
>> end
>>
>> class Track < Sequel::Model
>> many_to_one :album
>> one_to_one :studio
>> nested_attributes :studio
>>
>> def before_validation
>> self.studio_attributes = { name: "Default Studio" } if !studio
>>
>> super
>> end
>> end
>>
>> class Studio < Sequel::Model
>> one_to_one :track
>> end
>>
>> album = Album.create \
>> title: "Title",
>> tracks_attributes: [{
>> title: "First track",
>> studio_attributes: {
>> name: "MY favorite studio"
>> }
>> }]
>>
>> album = Album.first
>> album.update \
>> tracks_attributes: [{
>> id: album.tracks.first.id,
>> title: "Renamed"
>> }, {
>> title: "A New track",
>> studio_attributes: {
>> name: "My second favorite studio"
>> }
>> }]
>>
>> expected = "My second favorite studio"
>> actual = Track[title: "A New track"].studio.name
>>
>> raise "expected: #{expected}, actual: #{actual}" if expected != actual
>>
>>
>> For the new track being added in the update, the studio= setter is being
>> called twice because the studio association is nil in
>> Track#before_validation. We tracked it down to the
>> initialize_association_cache clearing the association via
>> tactical_eager_loading after studio_attributes= is first called.
>>
>> Is there a more conventional way to do this you could suggest or is it
>> indeed a bug?
>>
>
> First, thanks for providing a self-contained reproducible example. That
> makes things much easier.
>
> In terms of working around the issue, you could switch the
> before_validation to after_save, and don't use studio_attributes inside it:
>
> def after_save
> super
> self.studio ||= Studio.new(name: "Default Studio")
> end
>
> That should work fine if you don't need to do some special validation of
> the studio when saving the track. You don't need a presence validation or
> similar, since if there isn't a studio set when validating, you know one
> will be set after save.
>
> In terms of why your code doesn't work, it looks like it's due to a bug in
> tactical eager loading. Tactical eager loading will try to eager load for
> all objects if the current object doesn't have a cached association. It
> should probably only eager load for objects that don't have a cached
> association if the current object doesn't have a cached association. I
> committed a fix for this:
> https://github.com/jeremyevans/sequel/commit/288ae6f210842cbca54d3a18425117ad1d782ff4
>
> Your example was very helpful, it helped fix this bug, which has been
> present in tactical_eager_loading since it was originally introduced over
> 12 years ago.
>
> Thanks,
> Jeremy
>
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