finds unreferenced/dead methods

find_unreferenced.rb

# Usage: find app/models -name '*.rb' | xargs -n 1 ruby find_unreferenced.rb
require 'parser/current'

class ASTProcessor
  include AST::Processor::Mixin

  attr_reader :possibly_unreferenced

  def initialize
    @possibly_unreferenced = []
  end

  def handler_missing(node)
    process_all(node.children.select { |child| child.is_a? AST::Node })
  end

  def on_def(node)
    method_name = node.children[0]
    maybe_find_method(method_name)
  end

  def on_defs(node)
    method_name = node.children[1]
    maybe_find_method(method_name, prefix: "self.")
  end

  def maybe_find_method(method_name, prefix: "")
    search_term = Regexp.escape(method_name)
    search_term.gsub!(/=/, '\s*=')
    ag_term = "'(?!<\w)#{search_term}(?!\w)'"
    matches = `ag #{ag_term} -c --case-sensitive app lib`.rstrip
    lines = matches.each_line
    return if lines.count > 1
    if lines.first.split(':').last == '1'
      @possibly_unreferenced << (prefix + method_name.to_s)
    end
  end
end

include AST::Sexp
$file = ARGV[0]
ast = Parser::CurrentRuby.parse(File.read($file))
processor = ASTProcessor.new
processor.process(ast)
exit(0) if processor.possibly_unreferenced.none?
puts "Might be unreferenced (in #{$file}):"
processor.possibly_unreferenced.each { |method_name| puts "  - #{method_name}" }
exit(1)