CoseDellaVitaEx

Generic helpers for GraphQL API's.

Setup

1. Add to your dependencies:

   def deps do
     [
       {:cose_della_vita_ex, "~> 0.0.3"}
     ]
   end

2. Include the generic GraphQL types in your schema:

   defmodule MyApp.Schema do
     use Absinthe.Schema
     use CoseDellaVitaEx.Schema
   
     # Your own types here
   end

3. Create an error mapper:

   defmodule MyApp.ErrorMapper do
     alias CoseDellaVitaEx.ErrorMapper
   
     @behaviour ErrorMapper
   
     def map(%{custom_validation: :my_validation}, message): %MyError{message: message}
     # Add more custom errors here, then fall back to the included errors
     def map(opts, message), do: ErrorMapper.map_default(opts, message)
   end

Error handling

Convert Ecto changeset errors to GraphQL types.

1. Define possible errors for your mutation, so the client can match on those: The generic_error type will be used as a fallback

   defmodule MyApp.MyTypes
     alias CoseDellaVitaEx.Types.ErrorTypes
   
     @my_mutation_error_types [:my_error]
   
     union :my_mutation_error do
       types(unquote(@my_mutation_error_types))
       resolve_type(&ErrorTypes.resolve_error_type(&1, &2, @my_mutation_error_types))
     end
   
     object :my_mutation_result do
       field(:success, :boolean)
       field(:errors, list_of(:my_mutation_error))
     end
   end

Or if you do not have any specific errors to resolve you can also use the base mutation type:

defmodule MyApp.MyTypes
  object :my_mutation_result do
    import_fields(:base_mutation_payload)
  end
end

1. Automatically convert Ecto changeset errors in your resolver:

   defmodule MyApp.MyResolver do
     import CoseDellaVitaEx.Helpers
   
     alias MyApp.ErrorMapper
   
     def create(_parent, _fields, _resolution) do
       with {:ok, my_entity} <- MyDB.insert() do
         {:ok, %{my_entity: my_entity}}
       else
         {:error, %Ecto.Changeset{} = changeset} ->
           {:ok, add_changeset_errors(%{}, changeset, &ErrorMapper.map/2)}
       end
       |> format_success_errors()
     end
   end