AstSchemaMaterializer: Type used in directives is not detected as an additional type

[xsoufiane]

I wanted to construct a schema from the AST:

val schema = Schema.buildFromAst(graphql"""
    schema {
       query: Query
    }

    type Query {
      field: Int
      _service: _Service!
    }
  
    scalar _FieldSet
            
    scalar _Any
  
    type _Service {
       sdl: String
    }
  
    directive @extends on INTERFACE | OBJECT
  
    directive @external on FIELD_DEFINITION
  
    directive @requires(fields: _FieldSet!) on FIELD_DEFINITION
  
    directive @provides(fields: _FieldSet!) on FIELD_DEFINITION
  
    directive @key(fields: _FieldSet!) on OBJECT | INTERFACE
  """)

but the schema builder fails to detect the _FieldSet scalar, although _Any is detected 🤷‍♂️. The output of the render is:

type Query {
  field: Int
  _service: _Service!
}

scalar _Any

type _Service {
  sdl: String
}

directive @extends on INTERFACE | OBJECT

directive @external on FIELD_DEFINITION

directive @key(fields: _FieldSet!) on INTERFACE | OBJECT

directive @provides(fields: _FieldSet!) on FIELD_DEFINITION

directive @requires(fields: _FieldSet!) on FIELD_DEFINITION

[xsoufiane]

I think this is related to the findUnusedTypes in the builder:

builder.buildSchema(
  schemaInfo.definition,
  schemaExtensionDefs.toList,
  queryType,
  mutationType,
  subscriptionType,
  findUnusedTypes()._2.toList,
  BuiltinDirectives ++ directives,
  this
)

The findUnusedTypes function fails to detect the additionalType because it's used in the directives (compared to the unused _Any).