Ash Elixir•4mo ago

Using struct data in filter expressions

I think I've tried to do this a few times and have never gotten it to work properly. I have a calculation that takes a struct as an argument, and I want to use data from that struct in the expression, eg.

    calculate :valid_for_npc_and_topic,
              :boolean,
              expr(
                topic_id == ^arg(:topic) &&
                  (is_nil(speaker_faction_id) || speaker_faction_id == ^get_path(arg(:npc), :faction_id))
              ) do
      argument :topic, :string, allow_nil?: false
      argument :npc, :struct, allow_nil?: false, constraints: [instance_of: Resdayn.Codex.World.NPC]
    end

    calculate :valid_for_npc_and_topic,
              :boolean,
              expr(
                topic_id == ^arg(:topic) &&
                  (is_nil(speaker_faction_id) || speaker_faction_id == ^get_path(arg(:npc), :faction_id))
              ) do
      argument :topic, :string, allow_nil?: false
      argument :npc, :struct, allow_nil?: false, constraints: [instance_of: Resdayn.Codex.World.NPC]
    end

This doesn't error, but generates SQL like

ash_elixir_or((d0."speaker_faction_id"::text IS NULL)::boolean, (d0."speaker_faction_id"::text::text = NULL::text)::boolean)::boolean)::boolean)

(so the second part isn't working properly). It's probably something simple but I've tried lots of things like ^arg(:npc)[:id], ^ref([arg(:npc)], :id), and nothing else will even compile

Solution:

instead of ^get_path(arg(:npc), :faction_id) it should be get_path(^arg(:npc), :faction_id)

Jump to solution

8 Replies

sevenseacatOP•4mo ago

found this thread https://elixirforum.com/t/read-action-by-related-struct/61955/5?u=sevenseacat but

expr(topic_id == ^arg(:topic) && (is_nil(speaker_faction_id) ||
speaker_faction_id == (^arg(:npc))[:faction_id]))

doesn't work either - gives an error:

iex(48)> Ash.Query.for_read(Resdayn.Codex.Dialogue.Response, :for_npc, %{npc: habasi, topic: "bad people"}) |> Ash.read!()
** (Ash.Error.Unknown)
Bread Crumbs:
  > Exception raised in: Resdayn.Codex.Dialogue.Response.for_npc

Unknown Error

* ** (RuntimeError) Unsupported expression in Elixir.AshPostgres.SqlImplementation query: %{extra: %{}, name: :get_path, arguments: [%{<all of the NPC stuff>}, [:faction_id]], __struct__: Ash.Query.Function.GetPath, embedded?: false, __predicate__?: false, __function__?: true}
  (ash_sql 0.2.76) lib/expr.ex:2392: AshSql.Expr.default_dynamic_expr/6
  (ash_sql 0.2.76) lib/expr.ex:3241: AshSql.Expr.maybe_type_expr/6
  ...

iex(48)> Ash.Query.for_read(Resdayn.Codex.Dialogue.Response, :for_npc, %{npc: habasi, topic: "bad people"}) |> Ash.read!()
** (Ash.Error.Unknown)
Bread Crumbs:
  > Exception raised in: Resdayn.Codex.Dialogue.Response.for_npc

Unknown Error

* ** (RuntimeError) Unsupported expression in Elixir.AshPostgres.SqlImplementation query: %{extra: %{}, name: :get_path, arguments: [%{<all of the NPC stuff>}, [:faction_id]], __struct__: Ash.Query.Function.GetPath, embedded?: false, __predicate__?: false, __function__?: true}
  (ash_sql 0.2.76) lib/expr.ex:2392: AshSql.Expr.default_dynamic_expr/6
  (ash_sql 0.2.76) lib/expr.ex:3241: AshSql.Expr.maybe_type_expr/6
  ...

with the calculation being used in an action like:

    read :for_npc do
      argument :npc, :struct,
        allow_nil?: false,
        constraints: [instance_of: Resdayn.Codex.World.NPC]

      argument :topic, :string, allow_nil?: false

      filter expr(valid_for_npc_and_topic(npc: ^arg(:npc), topic: ^arg(:topic)))
    end

    read :for_npc do
      argument :npc, :struct,
        allow_nil?: false,
        constraints: [instance_of: Resdayn.Codex.World.NPC]

      argument :topic, :string, allow_nil?: false

      filter expr(valid_for_npc_and_topic(npc: ^arg(:npc), topic: ^arg(:topic)))
    end

ZachDaniel•4mo ago

We should make it simpler. But IIRC (^arg(:arg))[:foo] should work But if not we can make it work and/or fix the get_path version for example Maybe you could reproduce in a test in ash core?

sevenseacatOP•4mo ago

so its supposed to work? right. more investigation and/or a failing test

ZachDaniel•4mo ago

There is supposed to at least be some way to do it yes

sevenseacatOP•4mo ago

ahhhh I had the pin in the wrong place

ZachDaniel•4mo ago

But ^arg(:foo)[:path] doesn't work because of how pin operators work

Solution

sevenseacat•4mo ago

instead of ^get_path(arg(:npc), :faction_id) it should be get_path(^arg(:npc), :faction_id)

sevenseacatOP•4mo ago

(was looking through the tests for get_path in ash core)

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Using struct data in filter expressions

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