function Money.Ecto.Composite.Type.type/0 is undefined or private when using Ecto.Query.Api.type/2

[mjquinlan2000]

Versions

Elixir: 1.11.3 (compiled with Erlang/OTP 23) Ecto: 3.5.8 Erlang: 23.2.5 ex_money_sql: 1.4.3 ex_money: 5.5.1

The issue

I'm running into an issue where I am selecting a column and casting it to a composite money type with the type/2 function from Ecto.Query.API. Example:

MyModel
|> select([m], %{money: type(m.money, Money.Ecto.Composite.Type)})

And I get this error:

** (UndefinedFunctionError) function Money.Ecto.Composite.Type.type/0 is undefined or private. Did you mean one of:

      * type/1

The Ecto docs still specify type/0 as a valid callback so it's unclear to me why this was removed from Money.Ecto.Composite.Type. Any help would be greatly appreciated.

Thanks!

[mjquinlan2000]

I see you've been talking to Jose about this here https://github.com/elixir-ecto/ecto/issues/3558

Closing.

[mjquinlan2000]

Also mentioned here #12

[kipcole9]

@mjquinlan2000, thanks for raising the issue. As you found, this is fixed on Ecto master but not yet released on Hex. Nevertheless, you remind me I need to update documentation to note that using the type/2 macro is a different for a parameterised type versus one that is not.

[kipcole9]

Just looking at your query, are you sure you need to cast the type there? Usually it only needs to be cast when there are aggregate functions involved. Otherwise its type detection is pretty good, especially when using a schema as you are. ie does the following work?

MyModel
|> select([m], %{money: m.money})

[mjquinlan2000]

The actual query is in production code which is both very complex and proprietary so I can't really share it. I reduced it to the simplest query that would produce the error. I am just going to wait until type(t, {:parametarized, Money.Ecto.Composite.Type, []}) is out on Ecto

[kipcole9]

Ah, ok, thanks for the update. Make sense.

I have just added Money.Ecto.Composite.Type.cast_type/{0, 1} make the transition as easy as possible but this is clearly a breaking change in Ecto that I wasn't aware of. I would have made this a new type if I had known and I will send a PR for the ecto docs to make that clearer for others.

Any thoughts on how to handle the situation? I should have made this a major release but thats too late now.

Would creating a new type that is non-parameterised (ie same as the old behaviour) help you in this case?

[mjquinlan2000]

To be honest, the proposal on elixir-ecto/ecto#3558 (specifying parameterized in the type/2 call) seems like a messy contract.

In my opinion, Ecto.ParametarizedType should enforce a type/0 callback as well or figure out how to pass empty opts when no {:parameterized, Type, opts} tuple is passed to type/2

In addition, I would get rid of the type/2 implementation of using parameterized types and create a new parameterized_type/3 function in Ecto.Query.API that looks something like this parameterized_type(t, Money.Ecto.Composite.Type, opts) so that the contract is explicitly defined by the function name and not the pattern of the arguments.

However, I don't think there's anything to be done in this library so I can just wait for a new version of Ecto