snippet.rb

require 'yard'

class IncrementalArray
  def initialize(block) 
    @block = block
    @buffer = YARD::Parser::Ruby::Legacy::TokenList.new
  end
  def shift; fill_buffer; @buffer.shift end
  def first; fill_buffer; @buffer.first end
  def [](index) fill_buffer; @buffer[index] end
  
  private
  
  def fill_buffer
    @buffer.push(@block.call) if @buffer.empty?
  end
end

class IncrementalParser < YARD::Parser::Ruby::Legacy::StatementList
  def initialize(&block) @tokens = IncrementalArray.new(block) end
  public :next_statement
end

module YardObject
  def source
    return @source if @source
    methname = owner.name + '#' + name.to_s
    fname, line = *source_location
    @@file_cache ||= {}
    @@file_cache[fname] ||= File.readlines(fname)
    @@method_cache ||= {}
    if @@method_cache[methname]
      @source = @@method_cache[methname]
    else
      ws = @@file_cache[fname][line-1][/^(\s+)/, 1]
      parser = IncrementalParser.new { l = @@file_cache[fname][line-1]; line += 1; l }
      @source = ws + parser.next_statement.to_s
    end
  end
end

class Method; include YardObject end
class UnboundMethod; include YardObject end

class Foo
  # A docstring!
  def foo
    10.times do |i|
      puts "hello world #{i}"
    end
  end
end

f = Foo.new
puts f.method(:foo).source
# def foo
#   10.times do |i|
#     puts "hello world #{i}"
#   end
# end