Any way to limit a ListInputType argument to max entries?

Hi,

I’ve created custom arguments for scalar types like Int and String, where they have to be between some min and max but am a bit stumped on how to do this for Lists because there’s no coerce methods available. For example, given this argument

val idsArg = Argument("ids", OptionInputType(ListInputType(StringType)), ..)

how would I go about limiting it only max x entries? Is there any way to do this currently?

If you could point me in the right direction, that would be awesome!

Thanks

[bc-dima-pasieka]

👋 Quick update on how we resolved the case when the argument is passed as a variable (there are actually two cases to take into account)

1. Case when the variable is sent as a part of variables:

query getProducts($pageSize: Int) {
  products(first: $pageSize) {...}
}
{"pageSize": 10}

We create query validators (including our custom rule) dynamically with current variables injected and then just check the value by name:

case class CustomArgRule(variables: Json) extends ValidationRule {
  private val variablesMap: Map[String, Json] = ??? // convert json object to map so it's easier to use

  override def visitor(ctx: ValidationContext): AstValidatingVisitor = new AstValidatingVisitor {
    override val onEnter: ValidationVisit = {
      ...
      // when iterating through `Field` arguments you have access to variable name -
      // check if your variable exists in variables map
      case VariableValue(name, _, _) => variablesMap.get(name)
    }
  }
}

2. Case when the variable is NOT sent as a part of variables but has the default value:

query getProducts($pageSize: Int = 10) {
  products(first: $pageSize) {...}
}

case class CustomArgRule extends ValidationRule {

  override def visitor(ctx: ValidationContext): AstValidatingVisitor = new AstValidatingVisitor {
    override val onEnter: ValidationVisit = {
      ...
      // when iterating through `Field` arguments you have access to variable name -
      // find `OperationDefinition` among ancestors (it contains default variable values)
      // and check if your variable exists there
      case VariableValue(name, _, _) => extractVariableDefaultValue(name, ctx.typeInfo)
    }
  }

  private def extractVariableDefaultValue(
    variableName: String,
    typeInfo: TypeInfo
  ): Option[Value] =
    typeInfo
      .ancestors
      .collectFirst { case operation: OperationDefinition =>
        operation.variables.find(_.name == variableName).flatMap(_.defaultValue)
      }
      .flatten
}

[meddulla]

There are probably better ways to do it but here’s an example implementation in case it helps someone: https://gist.github.com/meddulla/d28b14d519cb22f677ee18bb2aaf1097