"Type ... cannot be used as an input" compilation error

I got compilation errors trying to implement simple mutation api. Possibly I’m doing something wrong but I wasn’t able to figure out what exactly.

Error:

Error:(18, 83) Type sangria.util.tag.@@[me.scf37.graphql1.PermissionInput,sangria.marshalling.FromInput.InputObjectResult] cannot be used as an input. Please consider defining an implicit instance of `FromInput` for it.
   implicit val MutationApiType = deriveContextObjectType[Ctx, MutationApi, Unit] {_.mutationApi}

Error:(18, 83) not enough arguments for method createWithoutDefault: (implicit fromInput: sangria.marshalling.FromInput[sangria.util.tag.@@[me.scf37.graphql1.PermissionInput,sangria.marshalling.FromInput.InputObjectResult]], implicit res: sangria.schema.ArgumentType[sangria.util.tag.@@[me.scf37.graphql1.PermissionInput,sangria.marshalling.FromInput.InputObjectResult]])sangria.schema.Argument[res.Res].
Unspecified value parameters fromInput, res.
   implicit val MutationApiType = deriveContextObjectType[Ctx, MutationApi, Unit] {_.mutationApi}

Code:

case class Permission(id: String, name: String, description: String)
case class PermissionInput(name: String, description: String)
case class Ctx(mutationApi: MutationApi)

trait MutationApi {
    @GraphQLField
    def permission(permission: PermissionInput): Permission = ???
}

object Main {
   implicit val PermissionType = deriveObjectType[Ctx, Permission]()
   implicit val PermissionInputType = deriveInputObjectType[PermissionInput]()
   implicit val MutationApiType = deriveContextObjectType[Ctx, MutationApi, Unit] {_.mutationApi}
}

Environment:

scalaVersion := "2.12.1"
Oracle 64-Bit Java "1.8.0_112"
Tried Sangria 1.0.0-RC5 and 4fe3952
sbt 0.13.13

[scf37]

It worked for me. In general, PLEASE consider adding scaladoc at least to public API. All that functional code with heaps of implicits is damn hard to decipher.

[jonas]

When using macros to derive context objects with methods you need to also declare an implicit JSON decoder for each of the input type associated with the method arguments. This is what is hinted in:

Please consider defining an implicit instance of `FromInput`

If you are using Spray JSON this would be something like:

object Main extends spray.json.DefaultJsonProtocol {
   implicit val PermissionType = deriveObjectType[Ctx, Permission]()
   implicit val PermissionInputType = deriveInputObjectType[PermissionInput]()
   implicit val PermissionInputJson = jsonFormat2(PermissionInput)
   implicit val MutationApiType = deriveContextObjectType[Ctx, MutationApi, Unit] {_.mutationApi}
}