log_subscriber.rb

# frozen_string_literal: true

require "active_support/log_subscriber"

module ActionView
  # = Action View Log Subscriber
  #
  # Provides functionality so that \Rails can output logs from Action View.
  class LogSubscriber < ActiveSupport::LogSubscriber
    VIEWS_PATTERN = /^app\/views\//

    def initialize
      @root = nil
      super
    end

    def render_template(event)
      info do
        message = +"  Rendered #{from_rails_root(event.payload[:identifier])}"
        message << " within #{from_rails_root(event.payload[:layout])}" if event.payload[:layout]
        message << " (Duration: #{event.duration.round(1)}ms | Allocations: #{event.allocations})"
      end
    end
    subscribe_log_level :render_template, :debug

    def render_partial(event)
      debug do
        message = +"  Rendered #{from_rails_root(event.payload[:identifier])}"
        message << " within #{from_rails_root(event.payload[:layout])}" if event.payload[:layout]
        message << " (Duration: #{event.duration.round(1)}ms | Allocations: #{event.allocations})"
        message << " #{cache_message(event.payload)}" unless event.payload[:cache_hit].nil?
        message
      end
    end
    subscribe_log_level :render_partial, :debug

    def render_layout(event)
      info do
        message = +"  Rendered layout #{from_rails_root(event.payload[:identifier])}"
        message << " (Duration: #{event.duration.round(1)}ms | Allocations: #{event.allocations})"
      end
    end
    subscribe_log_level :render_layout, :info

    def render_collection(event)
      identifier = event.payload[:identifier] || "templates"

      debug do
        message = +"  Rendered collection of #{from_rails_root(identifier)}"
        message << " within #{from_rails_root(event.payload[:layout])}" if event.payload[:layout]
        message << " #{render_count(event.payload)} (Duration: #{event.duration.round(1)}ms | Allocations: #{event.allocations})"
        message
      end
    end
    subscribe_log_level :render_collection, :debug

    module Utils # :nodoc:
      def logger
        ActionView::Base.logger
      end

    private
      def from_rails_root(string)
        string = string.sub(rails_root, "")
        string.sub!(VIEWS_PATTERN, "")
        string
      end

      def rails_root # :doc:
        @root ||= "#{Rails.root}/"
      end
    end

    include Utils

    class Start # :nodoc:
      include Utils

      def start(name, id, payload)
        return unless logger
        logger.debug do
          qualifier =
            if name == "render_template.action_view"
              ""
            elsif name == "render_layout.action_view"
              "layout "
            end

          return unless qualifier

          message = +"  Rendering #{qualifier}#{from_rails_root(payload[:identifier])}"
          message << " within #{from_rails_root(payload[:layout])}" if payload[:layout]
          message
        end
      end

      def finish(name, id, payload)
      end

      def silenced?(_)
        logger.nil? || !logger.debug?
      end
    end

    def self.attach_to(*)
      ActiveSupport::Notifications.subscribe("render_template.action_view", ActionView::LogSubscriber::Start.new)
      ActiveSupport::Notifications.subscribe("render_layout.action_view", ActionView::LogSubscriber::Start.new)

      super
    end

  private
    def render_count(payload) # :doc:
      if payload[:cache_hits]
        "[#{payload[:cache_hits]} / #{payload[:count]} cache hits]"
      else
        "[#{payload[:count]} times]"
      end
    end

    def cache_message(payload) # :doc:
      case payload[:cache_hit]
      when :hit
        "[cache hit]"
      when :miss
        "[cache miss]"
      end
    end
  end
end

ActionView::LogSubscriber.attach_to :action_view