Error when using :on_lookup for many_to_many sorted using expr_sort

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1

This is a followup on my previous question, I’ll paste here the relevant part:

   many_to_many :dishes, Dish do
      through DailyMenuDish
      join_relationship :daily_menu_dishes

      sort [Ash.Sort.expr_sort(parent(daily_menu_dishes.position))]

      source_attribute_on_join_resource :daily_menu_id
      destination_attribute_on_join_resource :dish_id
    end

I had this relationship and all was well if I just wanted to create it and display it in order using the position attribute on the join resource (see previous post).

Now I also wanted to update the dishes in the menu (to be precise, I transformed the create to be an upsert) and I’ve found the correct options to do so using manage_relationship but they work only if I comment out the sort option.

If I don’t, it fails with:

* ** (KeyError) key :parent_bindings not found in: %{
  sort: [
    {#Ash.Resource.Calculation.Expression<[expr: parent(daily_menu_dishes.position)]>,
     :asc}
  ],
  context: %{
    private: %{actor: nil, authorize?: false, in_before_action?: true},
    action: %Ash.Resource.Actions.Read{
      arguments: [],
      description: nil,
      filter: nil,
      get_by: [],
      get?: false,
      manual: nil,
      metadata: [],
      modify_query: nil,
      name: :read,
      pagination: false,
      preparations: [],
      primary?: true,
      touches_resources: [],
      transaction?: false,
      type: :read
    },
    actor: nil,
    authorize?: false,
    accessing_from: %{name: :dishes, source: MyApp.MenuManagement.DailyMenu},
    query_opts: [
      verbose?: false,
      actor: nil,
      authorize?: false,
      page: nil,
      return_query?: false
    ],
    initial_limit: 1,
    initial_offset: 0,
    page_opts: nil,
    initial_query: #Ash.Query<
      resource: MyApp.MenuManagement.Dish,
      filter: #Ash.Filter<name == "baz">,
      sort: [
        {#Ash.Resource.Calculation.Expression<[expr: parent(daily_menu_dishes.position)]>,
         :asc}
      ],
      limit: 1
    >,
    filter_requests: []
  },
  bindings: %{
    0 => %{type: :root, path: [], source: MyApp.MenuManagement.Dish}
  },
  resource: MyApp.MenuManagement.Dish,
  current: 1,
  calculations: %{},
  aggregate_defs: %{},
  in_group?: false,
  current_aggregate_name: :aggregate_0,
  aggregate_names: %{},
  parent_resources: []
}    at dishes, 2

    (ash 2.17.3) lib/ash/api/api.ex:2324: Ash.Api.unwrap_or_raise!/3
    iex:41: (file)

I wasn’t sure where to open an issue because on_lookup is from Ash core, while the :parent_binding error comes from Ash Postgres, let me know if it helps if I do it and if I need to provide some more information.

2

NGL I don’t think I considered the case of using parent in a relationship sort like that. Mind opening an issue on AshPostgres?

3

If you could PR a failing test that would be awesome too :slight_smile: I’ve got a few irons in the fire and a failing test would save me lots of time!

4

I’ve opened the issue and submitted a PR reproducing the failure

5

So, the issue here is actually pretty interesting. The basic issue is that we use the sort and the filter of a relationship to lookup potential matches, and if there is a parent reference then it doesn’t really make sense… :thinking: The only thing I can think to do is to ignore filters/sorts with parent references when managing relationships.

6

I’m not sure about filter, but I think ignoring the sort shouldn’t affect the result of manage_relationship, or is the order relevant?

7

The order could theoretically be relevant. But in this case, it makes sense that we can’t apply the filter or sort if they reference parent, because we are looking up some not currently related thing.

8

Your commit in main fixed this, thanks!

Relevant commit for posterity: