Replace included module with parser gem

README.md

$ cat mongo_mapper.rb
$ cat mongo_mapper.rb | ruby rewrite.rb
class Foo
  include Mongoid::Document

  key :name, String
end

mongo_mapper.rb

class Foo
  include MongoMapper::Document

  key :name, String
end

rewrite.rb

require "bundler/inline"

gemfile do
  source "https://rubygems.org"
  gem "parser", require: "parser/current"
end

class Rewriter < Parser::TreeRewriter
  def on_send(node)
    # Given `foo.bar(...)`,
    #   receiver    -> :foo
    #   method_name -> :bar
    #   *args       -> [...]
    receiver, method_name, *args = node.children

    # include Mongoid::Document
    # ~~~~~~~~~~~~~~~~~~~~~~~~~ node.loc.expression
    #         ~~~~~~~~~~~~~~~~~ args[0].loc.expression
    if receiver == nil && method_name == :include && args.size == 1 && args[0].loc.expression.source == "MongoMapper::Document"
      replace(node.loc.expression, "include Mongoid::Document")
    end

    super
  end
end

source = $stdin.read
buffer = Parser::Source::Buffer.new("(stdin)")
buffer.source = source
ast = Parser::CurrentRuby.parse(source)

puts Rewriter.new.rewrite(buffer, ast)