Spreading an inteface fragment inside a union

union_spread.rb

require "bundler/inline"

gemfile do
  gem "graphql", "1.11.2"
end

class Schema < GraphQL::Schema
  class Error < GraphQL::Schema::Object
    field :message, String, null: false
  end

  module Node
    include GraphQL::Schema::Interface
    field :id, ID, null: false
  end

  class Thing < GraphQL::Schema::Object
    implements Node
    field :name, String, null: false
  end

  class ThingOrError < GraphQL::Schema::Union
    possible_types Thing, Error
  end

  class Query < GraphQL::Schema::Object
    field :thing_or_error, ThingOrError, null: false

    def thing_or_error
      { name: "something", id: "1" }
    end
  end

  query(Query)
  use GraphQL::Execution::Interpreter
  use GraphQL::Analysis::AST
  
  def self.resolve_type(type, obj, ctx)
    Thing
  end
end


pp Schema.execute(<<-GRAPHQL).to_h
{
  thingOrError {
    ... on Thing {
      name
    }
    ... on Node {
      id
    }
  }
}
GRAPHQL

# {"data"=>{"thingOrError"=>{"name"=>"something", "id"=>"1"}}}