AshPhoenix.Form needs some way of maintaining order of nested records about ash_phoenix

[zachdaniel]

@sevenseacat feel free to reopen if you see more issues along these lines.

[zachdaniel]

So after thinking about this a bit more, I think the actual answer here is for the data to come back from the action with the resulting relationship loaded, and already sorted. This would only work in some cases, specifically when the entire relationship needs to be loaded, or in cases where we are performing a create action and are creating related records. However, if you aren't in one of those cases, you almost certainly aren't expecting to save the form and then get records back in the same order anyway, because if you load the relationship you'll get more than you sent back. So the pattern would look something like this:

case Form.submit(form) do
  {:ok, result} ->
     assign_form(socket, result)
   {:error, form} ->
     assign(socket, :form, form)
end

...

defp assign_form(socket, thing_you_are_updating) do
  thing_you_are_updating
  |> Api.load!([relationship: :foo], lazy?: true) # the `lazy?: true` will keep anything that is already loaded, and the edited relationship will be loaded as a result of the action
  |> AshPhoenix.Form.for_update(...)
end

[zachdaniel]

Actually...looks like we're already doing this in core :) @sevenseacat perhaps you could try using a lazy?: true load as illustrated above and see if that works for you?

[sevenseacat]

Originally the reason I was reloading all of the data was because relationships weren't coming back on the record after update, meaning re-rendering the form was erroring - that doesn't seem to happen anymore which is good! I can remove that reloading-data loop entirely.

However, the data is still being returned by the action in a different order.

eg.

    dbg(AshPhoenix.Form.value(socket.assigns.element_form, :tool_specifications))
    dbg(params)

    case AshPhoenix.Form.submit(socket.assigns.element_form, params: params) do
      {:ok, updated_element} ->
        dbg(updated_element.tool_specifications)

gives:

AshPhoenix.Form.value(socket.assigns.element_form, :tool_specifications) #=> [
  %{
    "_form_type" => "update",
    "id" => "abdab2a1-a221-43fe-be50-1add1a40cf8f",
    "quantity" => "1431",
    "specification_id" => "ea9544d9-5d5a-4014-9a59-335719bcd2ea",
  },
  %{
    "_form_type" => "update",
    "id" => "a3bc5d69-b683-4e42-83df-9a24eb9a2881",
    "quantity" => "21",
    "specification_id" => "022e2e06-fbe9-41d9-9860-4d67ca8a73c0",
  }
]

params #=> %{
  # other stuff
  "tool_specifications" => %{
    "0" => %{
      "_form_type" => "update",
      "_touched" => "_form_type,id,quantity,specification_id",
      "id" => "abdab2a1-a221-43fe-be50-1add1a40cf8f",
      "quantity" => "1431",
      "specification_id" => "ea9544d9-5d5a-4014-9a59-335719bcd2ea",
    },
    "1" => %{
      "_form_type" => "update",
      "_touched" => "_form_type,id,quantity,specification_id",
      "id" => "a3bc5d69-b683-4e42-83df-9a24eb9a2881",
      "quantity" => "21",
      "specification_id" => "022e2e06-fbe9-41d9-9860-4d67ca8a73c0",
    }
  }
}

updated_element.tool_specifications #=> [
  #MyApp.Element.ToolSpecification<
    specification: #MyApp.Tool.Specification<>,
    __meta__: #Ecto.Schema.Metadata<:loaded, "element_tool_specifications">,
    id: "a3bc5d69-b683-4e42-83df-9a24eb9a2881",
    quantity: 21,
    inserted_at: ~U[2022-10-17 06:16:24.635005Z],
    updated_at: ~U[2022-10-19 01:12:37.432723Z],
    element_id: "a8316188-2fe2-4ddb-a9b4-e02cb209bbac",
    specification_id: "022e2e06-fbe9-41d9-9860-4d67ca8a73c0",
    aggregates: %{},
    calculations: %{},
    __order__: nil,
    ...
  >,
  #MyApp.Element.ToolSpecification<
    specification: #MyApp.Tool.Specification<>,
    element: #Ash.NotLoaded<:relationship>,
    __meta__: #Ecto.Schema.Metadata<:loaded, "element_tool_specifications">,
    id: "abdab2a1-a221-43fe-be50-1add1a40cf8f",
    quantity: 1431,
    inserted_at: ~U[2022-10-17 05:53:26.206812Z],
    updated_at: ~U[2022-10-19 01:13:16.172939Z],
    element_id: "a8316188-2fe2-4ddb-a9b4-e02cb209bbac",
    specification_id: "ea9544d9-5d5a-4014-9a59-335719bcd2ea",
    aggregates: %{},
    calculations: %{},
    __order__: nil,
    ...
  >
]

[zachdaniel]

Okay, yeah I can see that. I guess the current behavior just doesn't do the work to preserve order. I'll take a look in the morning.

[zachdaniel]

I'm actually pretty sure its just reversing the inputs, because as we apply the inputs we do things like [result | relationship_value]. So I'll toss in an Enum.reverse in and I think we'll be good :)

[zachdaniel]

Alright, so this should be fixed in ash main. Anyone else looking: if you are loading data after submitting a form, you will want to use lazy?: true so as not to potentially reorder the relationship after editing it.