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Overriding Capistrano tasks

When re-defining a task in Capistrano v2, the original task was replaced. The Rake DSL on which Capistrano v3 is built is additive however, which means that given the following definitions

task :foo do
    puts "foo"
end

task :foo do
    puts "bar"
end

Will print both foo and bar.

But it is also possible to completely clear a task and then re-defining it from scratch. A Rake::Task provides the clear method for this, which internally performs three separate actions:

  • clear_prerequisites
  • clear_actions
  • clear_comments

Clearing the prerequisites (i.e. any dependencies that may have been defined for a task) is probably not what you want, though. Let’s say, for example, that you want to re-define the deploy:revert_release task, which is defined as follows:

task :revert_release => :rollback_release_path do
    # ...
end

Calling clear on this task and then re-defining it results in rollback_release_path never being called, thus breaking rollback behavior.

Under most circumstances, you will simply want to use clear_actions, which removes the specified task’s behaviour, but does not alter it’s dependencies or comments:

task :init do
    puts "init"
end

task :foo => :init do
    puts "foo"
end

Rake::Task["foo"].clear_actions
task :foo do
    puts "bar"
end

Running the foo task will print

init
bar

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