dead_constants.rb

#!/usr/bin/env ruby
gem "parser", "~> 1.4"
require "parser"
require "parser/ruby19"
require "set"

class ConstantDeclarationAndUseProcessor < Parser::AST::Processor
  attr_reader :declared, :used

  def initialize
    @declared = Set.new
    @used = Set.new
  end

  def dead_constants
    declared - used
  end

  def on_const(node)
    scope_node, name = *node
    used << name

    process(scope_node) if scope_node
  end

  def on_cdecl(node)
    scope_node, name, value = *node
    declared << name

    process(scope_node) if scope_node
    process(value) if value
  end

  def on_class(node)
    name_node, superclass_node, body_node = *node
    scope_node, name = *name_node
    declared << name

    process(scope_node) if scope_node
    process(superclass_node) if superclass_node
    process(body_node) if body_node
  end

  def on_module(node)
    name_node, body_node = *node
    scope_node, name = *name_node
    declared << name

    process(scope_node) if scope_node
    process(body_node) if body_node
  end
end

files = Dir["{lib,app,config}/**/*.{rb,rake}"].reject { |f| f =~ /generators.*templates/ }

processor = ConstantDeclarationAndUseProcessor.new

files.each do |file|
  begin
    source = Parser::Source::Buffer.new(file)
    source.source = File.read(file)
    ast = Parser::Ruby19.new.parse(source)
    processor.process(ast)
  rescue => e
    puts "\e[31;1m#{file}\e[0m"
    puts "#{e.class}: #{e.message}"
    puts e.backtrace
    puts
  else
    puts "\e[32;1m#{file}\e[0m"
  end
  $stdout.flush
end

File.open("dead_constants.txt", "w") do |f|
  processor.dead_constants.each do |sym|
    f.puts sym
  end
end