Context.arg Wraps Optional Arguments inside another Option

[SeanWhoCodes]

Overview

Given an argument MyArg of type Argument[Option[MyInputObject]], context.arg(MyArg) doesn't return a value of type Option[MyInputObject] within the 'resolve' function, but wraps the argument value inside another Option and returns Option[Option[MyInputObject]] instead.

Environment

This issue was verified in the following environment:

• sangria: 3.4.1
• sangria-circe: 1.3.2
• Scala: 3.2.1
• JDK: 17.0.5

Reproduction

Example Code

Below is an example that demonstrates the issue.

import io.circe.*
import sangria.ast.Document
import sangria.execution.Executor
import sangria.macros.*
import sangria.marshalling.*
import sangria.marshalling.circe.circeDecoderFromInput
import sangria.schema.*

import scala.concurrent.Await
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration.DurationInt
import scala.util.{Failure, Success}

object NestedOptionArgIssue {
  case class EchoMessageInput(message: String)

  given Decoder[EchoMessageInput] = (cursor: HCursor) =>
    for {
      message <- cursor.get[String]("message")
    } yield EchoMessageInput(message)

  given FromInput[EchoMessageInput] = circeDecoderFromInput[EchoMessageInput]

  val EchoMessageInputObjectType: InputObjectType[EchoMessageInput] =
    InputObjectType[EchoMessageInput](
      name = "EchoMessageInput",
      fields = List(
        InputField(name = "message", fieldType = StringType),
      ),
    )

  val MaybeEchoMessageInputArg: Argument[Option[EchoMessageInput]] =
    Argument[Option[EchoMessageInput]](
      name = "maybeEchoMessageInput",
      argumentType = OptionInputType(EchoMessageInputObjectType),
    )

  class GraphQLContext {
    def echoMessage(maybeEchoMessageInput: Option[EchoMessageInput]): Option[String] =
      maybeEchoMessageInput.map(input => s"Echoing message: ${input.message}")
  }

  val QueryType: ObjectType[GraphQLContext, Unit] =
    ObjectType[GraphQLContext, Unit](
      name = "Query",
      description = "GraphQL queries.",
      fields = fields[GraphQLContext, Unit](
        Field(
          name = "echoMessage",
          fieldType = OptionType(StringType),
          arguments = MaybeEchoMessageInputArg +: Nil,
          resolve = context => {
            val maybeInput = context.arg(MaybeEchoMessageInputArg) // 👈 Due to some reason, 'Context.arg' wraps the argument inside another Option.
            System.err.println(s"Surprisingly 'maybeInput' has a nested type 'Option[Option[EchoMessageInput]]': ${maybeInput.toString}")

            val flattenedInput = maybeInput.asInstanceOf[Option[Option[EchoMessageInput]]].flatten // 👈 So the casting is necessary to flatten the nested type.
            context.ctx.echoMessage(flattenedInput)
          },
        ),
      ),
    )

  val schema: Schema[GraphQLContext, Unit] = Schema[GraphQLContext, Unit](query = QueryType)

  private val queryWithArg: Document =
    graphql"""
      query {
        echoMessage(maybeEchoMessageInput: { message: "Hello World!" })
      }
      """

  def main(args: Array[String]): Unit = {
    val execute = Executor.execute(schema, queryWithArg, new GraphQLContext)

    Await.ready(execute, 10.seconds).value match {
      case Some(Success(result))    => println(s"Execution Result: $result")
      case Some(Failure(throwable)) => System.err.println(s"Execution Error: ${throwable.getMessage}")
      case None                     => ???
    }
  }
}

Behaviours

The following line from the example above is supposed to be Option[EchoMessageInput], but the log shows that the actual value is Some(Some(EchoMessageInput(Hello World!))), indicating Context.arg somehow wraps the argument value inside another Option.

val maybeInput = context.arg(MaybeEchoMessageInputArg)

Is there any misconfiguration in my example above that causes this undesired behaviour? Thank you.

[yanns]

Thanks for the detailed report. Sorry I missed the notification somehow.
At first sight, I thought it was similar to #434
But I'm not totally sure.

Could you open a PR with a failing test in https://github.com/sangria-graphql/sangria/blob/main/modules/core/src/test/scala/sangria/schema/ArgsSpec.scala ?

[SeanWhoCodes]

@yanns - No worries and I also just came back from my holiday.

As suggested, I raised #952 to demonstrate the unexpected behaviours related to arbitrary input objects and Args. From what I can see, the tests indicate the following:

• build with custom input argument: arguments of custom input types work fine as long as they are not optional;
• build with optional custom input argument and defined input: optional arguments of custom input types wrap the optional results inside another Option (e.g. Some(Some(CustomInput("Hello Sangria"))));

The findings above match what I observed previously, although circeDecoderFromInput from sangria-circe was used in my original code snippet, but I'm using argonautDecoderFromInput from sangria-argonaut in the tests to be consistent with other existing ones.

[yanns]

Thanks a lot for the PR!

By using @@ InputObjectResult, I could make it work: 4d81bbf

Is it something that also fix your case?

[SeanWhoCodes]

@yanns - Amazing! @@ InputObjectResult does fix the problem!

It makes sense to me now that we need the @@ tags in the following argument scenarios:

• Optional Object types: Argument[Option[EchoMessageInput @@ InputObjectResult]]
• Optional Scala types: Argument[Option[Int @@ CoercedScalaResult]]

Thanks so much for your help!