A little script to run RuboCop on a Ruby String from within Ruby

inline_runner.rb

require 'rubocop'
require 'tempfile'

class InlineRunner
  DEFAULT = RuboCop::Runner.new({}, RuboCop::ConfigStore.new)

  def initialize(runner: DEFAULT, filename: 'runner.rb')
    @runner = runner
    @file = Tempfile.new(filename)
  end

  def run(code)
    @file.write(code)
    @file.rewind

    @runner.run([@file.path])
  ensure
    @file.close
    @file.unlink
  end
end

runner = InlineRunner.new

example_code = 'class Wombat end'

runner.run example_code