Ash Framework Book - how to debug the actions

I might need to see how what your code looks like up to this point to say for sure. I believe there is a step in the book that addresses that.

To answer your question more directly, there are a few things you can do to debug an action/form.

With the form

With a form that has been returned in the {:error, form} case of AshPhoenix.Form, you can do

AshPhoenix.Form.errors(form, for_path: :all) |> IO.inspect()

Not all errors are displayed in the form automatically because they may not tie to fields that are editable in the form itself. We also log a warning (IIRC that is the level) when we encounter an error that could not be displayed to the user due to not implementing the AshPhoenix.FormData.Error protocol (a safety measure to avoid displaying internal details to the user.

You can also peek at form.source (or form.source.source, if you have a %Phoenix.Form{}

in the action itself

change fn changeset, _ -> 
  Ash.Changeset.after_transaction(changeset, fn result -> 
    IO.inspect(result)
    result
  end)
end

You can add a hook like this to display the ok/error result from the action.

You’ll want to make sure that your action is not accepting previous_names as an input, and that your change is being run in all necessary places to set the attribute, that it has a default of [] etc.

Thanks for your reply Zach. I inspected the result on save and go the following:

         errors: [
            %Ash.Error.Changes.InvalidChanges{
              fields: nil,
              message: "Change Tunez.Music.Changes.UpdatePreviousNames must be atomic, but could not be done atomically: Tunez.Music.Changes.UpdatePreviousNames does not implement `atomic/3`",

here is the update action:

    update :update do
      require_atomic? false
      accept [:name, :biography]
      change Tunez.Music.Changes.UpdatePreviousNames, where: [changing(:name)]
    end

I imagine the book should call this out, but the answer to that is to add require_atomic? false to the update action.

The action has require_atomic? false.

Hmm…now that is interesting

Would it be possible for you to push your code as you have it to Github? I can take a look

I noticed int he network tab that the app is falling back to longpoll, could this be a reason?

https://github.com/Raathmd/tunez.git

It needs to be change(changeset, opts, context), not change(changeset, context)

Also, I noticed you have duplicate migration files. That’s something that shouldn’t happen. You can not run mix ash.setup while there are duplicates. I assume you were experimenting with snapshots?

@ken-kost is correct about the def change/2 being the issue. This is an interesting one

We have logic for an Ash.Resource.Change to automatically perform its atomic/3 callback if there is no change/3 callback defined. So when we try to do that, we find that there is no atomic/3 callback either, and that produces this error.

Something common to do with behaviours in Elixir (which Ash.Resource.Change is one), is to use @impl true or @impl BehaviourModule above each function that implements a callback of that behaviour. You can read more about that here: Typespecs reference — Elixir v1.18.3

If you had @impl true above def change(changeset, context), you would get a warning about that not being an actual callback available.

I think there are two things that we can do on our end to improve this:

@sevenseacat we can make sure to use @impl true in all of our examples of change/validation/calculation callback functions.

And for myself, I can add a check that at least one of change/3, atomic/3 or batch_change/3 is defined, as that is the minimum required for a change to function. That check also would have surfaced this issue

Can do! I always forget to put that in everywhere