drakeviz.rb

#!/usr/bin/env ruby
#
# Graph dependencies from a Drakefile using Graphviz
#
# USAGE: drake --print +... | ruby drakeviz.rb out.png
#

require 'graphviz'

class Step < Struct.new(:inputs, :outputs)
  def each_edge(&block)
    inputs.product(outputs).each(&block)
  end
end

unless TARGET_FILENAME = ARGV[0]
  fail "missing TARGET_FILENAME"
end

steps = []
current_step = nil

# Parse output from `drake --print`

$stdin.each_line do |line|
  line_type, path = line.split

  case line_type
  when 'S'
    steps << current_step if current_step
    current_step = Step.new([], [])
  when 'I'
    current_step.inputs << path
  when 'O'
    current_step.outputs << path
  else
    $stderr.puts "Unknown line type: #{line_type.inspect}"
  end
end

steps << current_step


# Create a new graph
g = GraphViz.new(:G, :type => :digraph)

# Create an edge between each input and output of each step
steps.each do |step|
  step.each_edge do |input, output|
    g.add_edges(input, output)
  end
end

# Generate output image
g.output(:png => TARGET_FILENAME)