class GraphQL::StaticValidation::FieldsWillMerge

def validate(context)
  context.each_irep_node do |node|
    if node.ast_nodes.size > 1
      defn_names = Set.new(node.ast_nodes.map(&:name))
      # Check for more than one GraphQL::Field backing this node:
      if defn_names.size > 1
        defn_names = defn_names.sort.join(" or ")
        msg = "Field '#{node.name}' has a field conflict: #{defn_names}?"
        context.errors << GraphQL::StaticValidation::Message.new(msg, nodes: node.ast_nodes.to_a)
      end
      # Check for incompatible / non-identical arguments on this node:
      args = node.ast_nodes.map do |n|
        n.arguments.reduce({}) do |memo, a|
          arg_value = a.value
          memo[a.name] = case arg_value
          when GraphQL::Language::Nodes::VariableIdentifier
            "$#{arg_value.name}"
          when GraphQL::Language::Nodes::Enum
            "#{arg_value.name}"
          else
            GraphQL::Language.serialize(arg_value)
          end
          memo
        end
      end
      args.uniq!
      if args.length > 1
        msg = "Field '#{node.name}' has an argument conflict: #{args.map{ |arg| GraphQL::Language.serialize(arg) }.join(" or ")}?"
        context.errors << GraphQL::StaticValidation::Message.new(msg, nodes: node.ast_nodes.to_a)
      end
    end
  end
end