[GraphQL] @pp profiling

pp.rb

# frozen_string_literal: true

module Directives
  class Pp < GraphQL::Schema::Directive
    class Profiler < Types::BaseEnum
      graphql_name "PpProfiler"

      description "Available profilers for @pp directive"
      value :mem
      value :stack
      value :ruby
    end

    description "Profile the field resolving using one of the available profilers"

    locations(
      GraphQL::Schema::Directive::FIELD
    )

    argument :type, Profiler,
      required: true,
      description: "Profiler type"

    class << self
      def resolve(_object, arguments, context)
        field_name = context.query.selected_operation.selections.first.name
        msg = send(arguments[:type], field_name) do
          yield
        end
        $stdout.puts "\e[34m[PP] #{msg.join}\e[0m"
        context.namespace(:interpreter)[:runtime].write_in_response(["pp"], msg)
      end

      private

      def mem(field)
        require "memory_profiler"

        report_path = Rails.root.join("tmp/#{field}_memory.txt")

        MemoryProfiler.report { yield }.yield_self do |r|
          r.pretty_print(to_file: report_path)
        end

        ["Memory profile for #{field} is stored at: #{relative_path(report_path)}"]
      end

      def stack(field)
        require "stackprof"

        report_path = Rails.root.join("tmp/#{field}_stackprof.dump")

        StackProf.run(mode: :cpu, raw: true, out: report_path) do
          yield
        end

        [
          "StackProf dump is stored at: #{relative_path(report_path)}\n",
          "You can generate a JSON report by running the following command:\n\n",
          "   be stackprof --json #{relative_path(report_path)} > tmp/#{field}_stackprof.json\n\n",
          "Go to speedscope.app and analyze it!",
        ]
      end

      def ruby(field)
        require "ruby-prof"

        report_path = Rails.root.join("tmp/#{field}_rubyprof.txt")

        result = RubyProf.profile do
          yield
        end

        File.open(report_path, "w") do |f|
          RubyProf::FlatPrinter.new(result).print(f, min_percent: 1)
        end

        ["RubyProf report for #{field} is stored at: #{relative_path(report_path)}"]
      end

      def relative_path(path)
        Pathname.new(path).relative_path_from(Rails.root)
      end
    end
  end
end