Using the --rules option to trace the rule resolution

The relationship between tasks becomes the most difficult when the tasks are rules. In this case, a rule task may be suited for many task names. For example, when the rule specifies a regular expression instead of a name. In this case, the rules that were described previously won't help us anyway.

When you run a task that was accepted by a rule, it's very useful to know which task will be executed and in which order. Rake provides us with a --rules option to show us a rule's resolution. Take a look at the following Rakefile from Chapter 3, Working with Rules:

require 'rake/clean'

BOOK = 'book/book.asc'
CHAPTERS = FileList['book/*.asc'].exclude(BOOK)
DOCX_OUTPUT = 'output/%n.docx'
ODT_OUTPUT = 'output/%n.odt'

CLEAN.include('output/*.html')
CLOBBER.include('output')

namespace :generate do
  directory 'output'

  desc 'Generate only one article with given number'
  task :article, [:number] do |t, args|
    num = args.number
    article...