class_name usage with Engines

[michaelbrawn]

I was unable to find in your documentation that when when you're using an engine and you want to use class_name, you need to namespace the class.

it do 
      should have_many(:friends).
      with_foreign_key('engine_friend_id').
      class_name('Friend')
end

This works correctly:

it do 
      should have_many(:friends).
      with_foreign_key('engine_friend_id').
      class_name('Engine::Friend')
end

[mcmire]

I'm not too familiar with engines -- if you put a model under the namespace for your engine, does the engine automatically import that model into the global namespace?

Also, what does the corresponding has_many line in your model look like?

[michaelbrawn]

If you namespace the model, it does automatically import that model into the global namespace. So the second block of code does work there.

Here's the has_many line in model.

has_many :friends, foreign_key: "engine_friend_id", class_name: "Friend"

Name spacing the model did work, although it wasn't immediately obvious when looking at the just the association from the model and the shoulda-matchers documentation. With hindsight being 20/20, I see that I should have realized to namespace the model as every model referenced in my spec tests are name spaced. I just thought it might be worth mentioning in the class_name section in the documentation.

[mcmire]

Well, it's just strange to me. If Rails automatically imports the model into the global namespace then shoulda-matchers should be able to find it, because you load Rails in your tests. I can take a look at what the code currently does to see if there's an improvement we can make there.

[mcmire]

@michaelbrawn I'm re-reviewing this issue and I just want to understand the context here. Were you trying to write tests for a model inside of an engine? If so, this would make sense why you can simply use class_name: "Friend" for the has_many call -- what ActiveRecord may be doing is trying to look for Friend within the surrounding namespace of the model (since has_many is called within the context of the model, and the model knows what its name is and hence which namespace it's in). Given this, what do you think about this copy to add this to the docs for have_many?

If the model you're testing is in an engine, you may have declared the has_many association with a class_name that excludes the engine's namespace. While ActiveRecord will resolve the class name against this namespace automatically, we do not, so you'll want to make sure you include the namespace when you use have_many. For instance, this association:

has_many :friends, class_name: "Friend"

should be tested like so:

should have_many(:friends).class_name("MyEngine::Friend")

and not like so:

should have_many(:friends).class_name("Friend")

[michaelbrawn]

@mcmire I was trying to write test for a model inside of an engine. That documentation looks right. 👍

[mcmire]

@michaelbrawn This is now fixed in b4bf814. (I just opted to fix the class_name option so it'll look inside the model namespace first before looking in the global namespace.)

[michaelbrawn]

That's Great! 👍