Struggling getting dialyzer to accept my @spec

Questions / Help
1

Hi,

I have the following module:

defmodule MyApp.Payment
  use Ecto.Schema

  import Ecto.Changeset

  schema "payment" do
      field :booking_uuid, :string

      belongs_to :booking, Kraken.Bookings.Booking
  end

  @spec update_payment_booking(__MODULE__, integer(), String.t()) :: Ecto.Changeset.t()
  def update_payment_booking(payment, booking_id, booking_uuid) do
    payment
    |> change(%{booking_id: booking_id, booking_uuid: booking_uuid})
  end
end

VS code highlights this spec with a warning stating it is invalid. I don’t understand this as the function takes an instance of itself, an integer and a string, returning a changeset. When I ask VS code to auto complete it for me, it replaces it with:

@spec update_payment_booking(
          {map, map}
          | %{
              :__struct__ => atom | %{:__changeset__ => any, optional(any) => any},
              optional(atom) => any
            },
          any,
          any
        ) :: Ecto.Changeset.t()

Can someone please run me through why it thinks my spec is wrong?

Thanks in advance

2

Can you show us the callers of that function? Maybe indeed some of them pass a tuple as a first parameter to it?

3

Thanks for replying,

Sure, it gets called once in my codebase:

 defp handle_confirm_booking_response({:ok, %{booking: booking}}, payment) do
    updated_payment =
      Payment.update_payment_booking(payment, booking.id, booking.uuid)
      |> Payment.update_payment_status(:captured)
      |> Repo.update!()

And I can confirm the first argument in that payment is indeed a Payment struct.

Just for my own info does that mean dialyzer will mark a spec as invalid if it is called with different arguments in a different module? I assumed it would just highlight the offending call rather than the spec itself,

Thanks

4

I don’t think the __MODULE__ looks right there. It resolves to MyApp.Payment which is the atom :"Elixir.MyApp.Payment and it looks like you’re passing in an instance of the of the schema. Did you mean to write %__MODULE__{} instead?

Or you could do something like

@opaque t :: %__MODULE__{}

@spec update_payment_booking(t(), integer(), String.t()) :: Ecto.Changeset.t()`

(Edited to s/your/you’re/)

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5

I can confirm %__MODULE__{} clears the warning - Thanks for your explanation which makes sense!

1 Like
6

You probably want __MODULE__.t(). There was even recent discussion here or simply t() as @paulanthonywilson pointed out.

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