Rails 2 to Rails 3: find duplicate callback registrations

find_duplicate_callback_declarations.rb

# When moving from Rails 2 to Rails 3 a change in
# callback behavior can cause issues because
# you can now only have one callback that calls a
# specific method, e.g.
#
#  after_save :foo, if: :bar?
#  after_save :foo, if: :baz?
#
# In the above only the second callback will be stored. The first
# one with the condition on bar? will not appear in the callback chain.
#
# This is the line in ActiveSupport that causes this to happen:
#   https://github.com/rails/rails/blob/0c0f278ab20f3042cdb69604166e18a61f8605ad/activesupport/lib/active_support/callbacks.rb#L500
#
# This is how Rails works up to Rails 5.2 as well. Haven't checked 6.0 yet.

dirs2check = %w(app config lib spec vendor)
duplicates = []
failed = []

dirs2check.each do |dir|
  Dir["#{dir}/**/*.rb"].each do |file|
    file_duplicates = []
    begin
      contents = File.read(file)
    rescue => ex
      failed << "#{filed} failed to be read because of #{ex.message}"
      next
    end
    hash = {}
    begin
      contents.scan(/\b((after|before)_(save|update|commit|destroy))[ \(](:\w+)/).map do |callback, _, _, method|
        key = "#{callback} #{method}"
        if hash.key?(key)
          file_duplicates << "#{file}: #{key} is duplicated"
        else
          hash[key] = true
        end
      end
    rescue => ex
      failed << "#{file} failed to be read because of #{ex.message}"
      next
    end
    if file_duplicates.empty?
      puts "#{file} \e[32mno duplicates\e[0m"
    else
      duplicates.concat file_duplicates
    end
  end
end

puts
puts
puts "Duplicates found: #{duplicates.length}"
puts duplicates
puts
puts "Failures:"
puts failed