raketree.rb

# This extends the behavior of Rake to allow you to see all of the dependencies
# of a Rake task recursively, not just the immediate dependencies.
#
# It adds a -d option (also called --dependency-tree).  Left blank, this
# option shows you dependencies for all Rake tasks.  Alternatively, you
# can pass a regular expression to this option and it will only show
# dependencies for matching tasks.
#
# To use this special version of Rake, save it in a Ruby file called
# raketree.rb (but the name really doesn't matter).  Here are some examples of
# how to invoke it:
#
#   $ ruby raketree.rb -h   #--> shows help
#   $ ruby raketree.rb -T   #--> lists all Rake tasks
#
# Here are some examples of how to use the special dependency-tree
# functionality:
#
#   $ ruby raketree.rb -d        #--> shows dependencies for all rake tasks
#   $ ruby raketree.rb -d db     #--> shows dependencies for all rake tasks
#                                     that match the regex /db/
#   $ ruby raketree.rb -d t?st   #--> shows dependencies for all rake tasks
#                                     that match the regex /t?st/
#

#**********************************************************
# LOAD RAKE
#******

begin
  require 'rake'
rescue LoadError
  require 'rubygems'
  require 'rake'
end

#**********************************************************
# CUSTOMIZE RAKE
#******

module Rake

  class Application

    # Add our own custom Rake option.
    alias_method :old_standard_rake_options, :standard_rake_options
    def standard_rake_options
      old_standard_rake_options <<
        ['--dependency-tree', '-d [PATTERN]', "Display all the dependencies for tasks (matching optional PATTERN) then exit.",
          lambda { |value|
            options.dependency_tree = true
            options.show_task_pattern = Regexp.new(value || '')
          }
        ]
    end

    # Redefine this method so that it calls our own display_dependency_tree method.
    def top_level
      standard_exception_handling do
        if options.show_tasks
          display_tasks_and_comments
        elsif options.show_prereqs
          display_prerequisites
        elsif options.dependency_tree
          display_dependency_tree
        else
          top_level_tasks.each { |task_name| invoke_task(task_name) }
        end
      end
    end

    def display_dependency_tree
      displayable_tasks = tasks.select do |t|
        t.comment && t.name =~ options.show_task_pattern
      end
      for task in displayable_tasks
        $indent = 0
        puts task.name
        display_dependent_tasks(task)
      end
    end
    
    def display_dependent_tasks(task)
      $indent += 1
      for t in task.dependencies
        if t.is_a? String
          # No Rake Task object could be built to represent this,
          # so we just display it.
          puts('  ' * $indent + t)
        elsif t.is_a? FileTask
          # We choose not to display FileTasks.  A Rake task can be defined
          # to depend on the timestamps of files; hence the need for
          # FileTasks.  If we chose to display FileTasks, the rdoc task
          # would display a long list of files as dependencies.
        else
          puts('  ' * $indent + t.name)
          display_dependent_tasks(t)
        end
      end
      $indent -= 1
    end

  end

  class Task
    
    def dependencies
      result = []
      # @prerequisites is an array of strings that name tasks
      for p in @prerequisites
        begin
          result << Task[p]  # build a Task object from the task name
        rescue
          # the Task object could not be built, so we just remember the name
          result << p
        end
      end
      result
    end

  end
end

#**********************************************************
# INVOKE RAKE
#******

Rake.application.run