argOpt returns unexpected type at runtime

[cneijenhuis]

Given an argument like this:

val OptionalStringArg: Argument[Option[String]] = Argument("foo", OptionInputType(StringType))

I'd expect that argOpt returns Option[Option[String]]. The compiler also thinks so, however at runtime I get Option[String].

val t1: Option[Option[String]] = ctx.argOpt(OptionalStringArg)
val t2: Option[String] = ctx.argOpt(OptionalStringArg) // Does not compile

println(t1) // prints "Some(foobar)", instead of the expected "Some(Some(foobar))"

I believe this instanceOf is to blame: https://github.com/sangria-graphql/sangria/blob/master/src/main/scala/sangria/schema/Context.scala#L301

[paulpdaniels]

I'm not sure that type of argument makes much sense in GraphQL, what would the schema for an option of an option of a string look like?

[cneijenhuis]

Right, it looks a little strange without context 😉 I wanted to use this inside a middleware. The middleware is called for any field, including fields that don't have this argument declared in the schema. Therefore:

• None - the field does not have the argument
• Some(None) - the field has the argument, but it was not set

I don't really need that distinction, but I can't call arg() instead of argOpt() because it will throw an exception in the first case.

My workaround is to first check if the field has the argument at all, and only if so, call arg().