newtype encoding for query param does not match decoding by Servant

[jwoudenberg]

First of all, thank you for your work in creating this library!

I've hit a small snag: I have a newtype that is used as a capture parameter in an endpoint:

newtype Id = Id Int32 deriving ( Eq, Generic, Show, FromHttpApiData)

type API = Capture "id" Id :> ReqBody '[ JSON] Resource :> Put '[ JSON] NoContent

The generated API function generates a URL that looks like this: /Id%206, because it whereas servant's default decoder for this newtype expects a URL that simply reads /6. It looks like this happens when the Elm version of the newtype (type Id = Id Int) is passed through toString.

Is there something I can do to make this work, short of getting rid of getting rid of the newtype?

One potential avenue: We also generate an elm encodeId : Int -> Json.Encode.Value function. If for encoding the parameter in the query string we'd call that function first, then encode the Json value into a string it looks like we would generate the correct URI.