scalar CustomScalar @specifiedBy(url: "https://example.com")

input WithList {
  list: [String!]
}

type Query {
  foo(arg: [CustomScalar!]!): String!
  bar(arg: [String!]): String!
  list(arg: WithList): String!
}

{
  a: foo(arg: [null, 1])
  b: foo(arg: [null, null, "hello"])
  bar(arg: [null])
  list(arg: {list: ["ok", null]})
}