Defining scalar type with absinthe

Hi everyone, so working with graphql and absinthe, I tried to define scalar type :tags witch is just list of string like: ["one", "two", "etc"]
and you can define it like field :tags , list_of(:string). But having then transform this list to just one string "one, two, etc" it would be much better having a custom type! So after trying figured out how is defined List in absinth i ended up with this implementation: `

scalar :tags do
    parse(fn input ->
      with %Absinthe.Blueprint.Input.List{items: list} <- input do
        tags = 
          Enum.reduce(list, "", fn  %{normalized: %{value: value}}, acc -> acc <> value <> ", " 
                                   _, acc -> acc end)
        {:ok, tags}
      else
        _ -> :error
      end
    end)

    serialize(fn tags -> String.split(tags, ", ") end)
  end

Witch isn’t the best but should give me at least "one, two, etc," But instead it gives me error:

“Argument “input” has invalid value $input.\nIn field “tags”: Expected type “Tags”, found [“one”, “two”, “etc”].”

if i change inside input field from :tags to list_of(:string) everything work but then i need to transform list inside my app domain, witch look not so clean. IO.inspecting input get:

%Absinthe.Blueprint.Input.List{
  errors: [],
  flags: %{},
  items: [
    %Absinthe.Blueprint.Input.Value{
      data: nil,
      normalized: %Absinthe.Blueprint.Input.String{
        errors: [],
        flags: %{},
        schema_node: nil,
        source_location: nil,
        value: "one"
      },
      raw: %Absinthe.Blueprint.Input.RawValue{
        content: %Absinthe.Blueprint.Input.String{
          errors: [],
          flags: %{},
          schema_node: nil,
          source_location: nil,
          value: "one"
        }
      },
      schema_node: nil
    },
  ...}

So pattern matching and my function works, so how i can define list_of(:string) == :tags ?
I read the book but still can’t figured out this… Please if some one know where to find answers or how to solve this issue, i would be very grateful :wink:

2 Likes

I have the same problem, ’ opened an issue on github (https://github.com/absinthe-graphql/absinthe/issues/670)

1 Like

Thank you! I read Ben answer. I already supposed it was’t possible, I just used primary types. I also tried using middleware before it hit resolvers but it din’t work…