class GraphQL::StaticValidation::FragmentsAreFinite

def get_spreads(selection)
  case selection
  when GraphQL::Language::Nodes::FragmentSpread
    [selection]
  when GraphQL::Language::Nodes::Field, GraphQL::Language::Nodes::InlineFragment
    get_spreads(selection.selections)
  when Array
    selection.map { |s| get_spreads(s) }.flatten
  end
end

def has_nested_spread(fragment_def, parent_fragment_names, context)
  nested_spreads = get_spreads(fragment_def.selections)
  nested_spreads.any? do |spread|
    nested_def = context.fragments[spread.name]
    parent_fragment_names.include?(spread.name) || has_nested_spread(nested_def, parent_fragment_names + [fragment_def.name], context)
  end
end

def validate(context)
  context.visitor[GraphQL::Language::Nodes::FragmentDefinition] << -> (node, parent) {
    if has_nested_spread(node, [], context)
      context.errors << message("Fragment #{node.name} contains an infinite loop", node, context: context)
    end
  }
end