A better way to diff the before/after output of rake routes

route_diff.rb

#!/usr/bin/env ruby
# frozen_string_literal: true

# Usage:
#
# ```
# bin/rake routes > tmp/routes_before
# # edit routes.rb
# bin/rake routes > tmp/routes_after
# bin/dev/route_diff.rb tmp/routes_before tmp/routes_after
# ```
#
# Example output:
#
# ```
# Route sets are not equal
# Number of routes: File 1: 380, File 2: 380
# Routes in both files: 379
# Routes in file1 not in file2: 1
# 	logout	GET	/logout(.:format)	user_sessions#destroy
# Routes in file2 not in file1: 1
# 	logout	GET	/low_gut(.:format)	user_sessions#destroy
# ```

require 'set'

class RouteDiff
  class Route
    attr_reader :name, :verb, :path, :action, :options

    def initialize(name, verb, path, action, options)
      @name = name.to_s.strip
      @verb = verb.to_s.strip
      @path = path.to_s.strip
      @action = action.to_s.strip
      @options = options.to_s.strip
    end

    # Alternate constructor
    def self.parse(line)
      parts = line.split
      case parts.length
      when 3
        new(nil, *parts, nil)
      when 4
        new(nil, *parts)
      when 5
        new(*parts)
      else
        raise(
          format(
            'Unable to parse line: Expected 4-5 parts, got %d: %s',
            parts.length,
            line
          )
        )
      end
    end

    # Because we will have two `Set`s composed of `Route`s, we must
    # define `eql?` and `hash`.
    def eql?(other)
      @name == other.name &&
        @verb == other.verb &&
        @path == other.path &&
        @action == other.action &&
        @options == other.options
    end

    # Because we will have two `Set`s composed of `Route`s, we must
    # define `eql?` and `hash`.
    def hash
      @_hash ||= [@name, @verb, @path, @action, @options].join.hash
    end

    def to_s
      [@name, @verb, @path, @action, @options].join("\t")
    end
  end

  class Diff
    def initialize(file1, file2)
      @routes1 = parse(file1)
      @routes2 = parse(file2)
    end

    def run
      if @routes1 == @routes2
        puts 'Route sets are equal'
      else
        diff
      end
    end

    private

    def diff
      puts 'Route sets are not equal'
      diff_totals
      diff_intersection
      diff_left
      diff_right
    end

    def diff_intersection
      intersection = @routes1 & @routes2
      puts format("\nRoutes in both files: %d", intersection.size)
    end

    def diff_left
      left = @routes1 - @routes2
      puts format("\nRoutes in file1 not in file2: %d", left.size)
      left.each { |route| puts route }
    end

    def diff_right
      right = @routes2 - @routes1
      puts format("\nRoutes in file2 not in file1: %d", right.size)
      right.each { |route| puts route }
    end

    def diff_totals
      puts(
        format(
          "\nNumber of routes: File 1: %d, File 2: %d",
          @routes1.size,
          @routes2.size
        )
      )
    end

    def parse(file)
      lines = File.readlines(file)
      lines.shift # discard first line (column headers)
      Set.new(lines.map { |line| Route.parse(line) })
    end
  end
end

RouteDiff::Diff.new(*ARGV).run