Warning found duplicate primary keys for association/embed in liveview with nested cast_assoc changeset

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,
1

Hey,

I have a liveview application with a nested changeset.

There is study on top.
This has a cast_assoc for scenarios.
And scenarios has a cast_assoc for scenario_tasks.

I am having a problem on the scenario tasks level.

When I add a 3rd new scenario_task in liveview I am seeing this warning:

[warning] found duplicate primary keys for association/embed :scenario_tasks in Scenario. In case of duplicate IDs, only the last entry with the same ID will be kept. Make sure that all entries in :scenario_tasks have an ID and the IDs are unique between them

I think this is because now in cast there are multiple scenario_tasks with nil for id.

This seems to not cause any problems for add/update, but when I am deleting these entries either all of them go at once, or the last 2 go at once.

I am also not sure if the interaction with the changeset is correct (legacy code).

Add is done like this:

  def handle_add_task(socket, scenario_i) do
    {scenario_index, _rem} = Integer.parse(scenario_i)

    study_changeset = socket.assigns.study_changeset
    scenarios = Ecto.Changeset.get_field(study_changeset, :scenarios, []) || []
    nth_scenario = Enum.at(scenarios, scenario_index)

    updated_tasks = nth_scenario.scenario_tasks ++ [%{title: ""}]

    nth_scenario_with_new_task =
      Ecto.Changeset.change(nth_scenario, %{scenario_tasks: updated_tasks})

    scenarios_with_i_updated =
      List.replace_at(scenarios, scenario_index, nth_scenario_with_new_task)

    updated_study_changeset =
      Ecto.Changeset.put_change(study_changeset, :scenarios, scenarios_with_i_updated)

    {:noreply, assign(socket, study_changeset: updated_study_changeset)}
  end

Remove is done like this:

  def handle_event("remove_task", %{"task" => task_i, "scenario" => scenario_i}, socket) do
    {scenario_index, _rem} = Integer.parse(scenario_i)
    {task_index, _rem} = Integer.parse(task_i)

    study_changeset = socket.assigns.study_changeset

    scenarios = Ecto.Changeset.get_field(study_changeset, :scenarios, []) || []

    nth_scenario = Enum.at(scenarios, scenario_index)

    scenario_tasks = Ecto.Changeset.get_field(nth_scenario, :scenario_tasks, [])

    updated_tasks = List.delete_at(scenario_tasks, task_index)

    nth_scenario_changeset = Ecto.Changeset.change(nth_scenario, %{scenario_tasks: updated_tasks})

    updated_scenarios = List.replace_at(scenarios, scenario_index, nth_scenario_changeset)

    study_changeset = Ecto.Changeset.put_change(study_changeset, :scenarios, updated_scenarios)

    {:noreply, assign(socket, study_changeset: study_changeset)}
  end

My questions would be, is the handling of the changes to the changeset fine this way?
Any ideas how to handle the duplicate primary keys warning?

Thank you

2

More or less got it sorted, this helped: Warning about duplicated primary keys for new records · Issue #3514 · elixir-ecto/ecto · GitHub
I am changed ti code, to not pass tasks as structs, but always as maps.

3

I’ve encountered this before when doing “add another” kinds of patterns, but I haven’t written the blog post I’ve been promising myself I’d write yet.

The short short version: put_change does not like seeing action: :replace changesets in its input for IDs it already has one for, so filter them out.

This replicates the behavior of changesets in old-school server-side rendering: phoenix_ecto skips them altogether when generating inputs:

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