This breaks ActiveStorage associations for UUID primary keys. It also breaks has_many with the through option with UUID primary keys.

This correctly worked in 5.2.3, and all of the intermediate classes correctly define their associations. So this seems like a regression.

@ekampp Can you open an issue and reproduce the problem in the bug report template? Thanks!

I guess I can, but wouldn't it be better to have some more thorough tests rather than everybody having to open individual bug reports on every ID type?

I see this in the code for this PR: active_record.type_for_attribute(active_record.primary_key).type != :integer

This will always trigger the NotImplementedError for anything other than integers, right?

I guess I can, but wouldn't it be better to have some more thorough tests rather than everybody having to open individual bug reports on every ID type?

That isn't really the point. I want to see why this change is causing you trouble first before we try and fix anything. Also, we can only guess at how to solve a problem without reproduction steps.

This will always trigger the NotImplementedError for anything other than integers, right?

If you don't have the correct associations in place to properly type cast IDs, yes. Please read the issue this PR fixes for context.

If you don't have the correct associations in place to properly type cast IDs, yes.

I don't actually see any tests in this PR for any PK types other than integers? So how are you even sure that your PR correctly handles anything other than Integers?

This is a fairly complex guard for you to be that confident that you're not accidentally breaking non-integer PK types.

In any case. Here is the demo project that illustrates the problem.

The error message I'm getting is:

In order to correctly type cast [sic] Structure.id, Account needs to define a :project association.

But the account doesn't have a single project association and nor should it have a single one. It has multiple project associations which is entirely correct and by design. So the error message seems to also be incorrect.

This is still a problem with has_many :through when using UUIDs for primary keys:

# Table name: documents
#
#  id          :uuid             not null, primary key
class Document < ApplicationRecord
  has_many :sections
  has_many :paragraphs, through: :sections
end

# Table name: sections
#
#  id                      :uuid             not null, primary key
#  document_id             :uuid
class Section < ApplicationRecord
  belongs_to :document
  has_many :paragraphs
end

# Table name: paragraphs
#  id            :uuid             not null, primary key
#  section_id    :uuid             not null
class Paragraph < ApplicationRecord
  belongs_to :section
end

irb(main)> document.paragraphs
Traceback (most recent call last):
        1: from (irb):5
NotImplementedError (In order to correctly type cast Document.id, Payment needs to define a :sections association.)

Not just :uuids, custom ::ActiveRecord::Type's don't work either. See https://stackoverflow.com/questions/60242514/rails-custom-activerecordtype-fails-when-using-class-name-in-has-many-throu

Updated #38340 to reflect that @crispinheneise and @mattes. Thank you.

I added a test script to reproduce this error in #38340 (comment)