In building out some complex deployments, I seem to continually have
the need to have helper methods for my tasks. The way I've done it and
the way I see capistrano-ext does this, is to just define the helpers
alongside your task definitions:
Capistrano::Configuration.instance(:must_exist).load do
def something_interesting; end
end
This works fine and all, but I have the same problem with this that I
have with doing this in rake tasks, that is, there is no scoping to
these method definitions. This is worse in rake tasks, since doing
this in a rake task defines the method on Object, but it still feels
bad to me. The practical problem I've found is it makes it hard to
track down where those methods are defined.
My way of solving this with rake tasks (and others like rSpec seem to
solve this) is by having subclasses of Rake::Task. I looked into doing
this for capistrano, and I think it would just mean a little
refactoring around the Capistrano::Configuration::Namespaces#task
method. Before diving into this though, I wanted to see if anyone sees
any downside to this or if there's some other common pattern to this
I'm missing.
You could also define helper classes and put the methods in there, but
often you need access to the run/sudo/... functionality which would
require injecting capistrano classes into the helpers. I'm not sure if
that seems semi-elegant or semi-clunky, but I still feel that it
should be solved with a custom TaskDefinition. It does seem flexible,
but that the usage would be complicated.
For conversation's sake, an example:
Capistrano::Configuration.instance(:must_exist).load do
namespace :data do
desc "Verifies that the data version is as expected"
task :verify_version => :environment, :roles => :db do
run_rake("data:verify_version")
end
end
def run_rake(*args); run(build_rake_command(*args)); end
def system_rake(*args); system(build_rake_command(*args)); end
def sudo_rake(*args); sudo(build_rake_command(*args)); end
end
I'd want to implement those methods as:
module Capistrano
class RakeTaskDefinition
def (run,system,sudo)_rake....
end
def rake_task(*args)
RakeTaskDefinition.define_task(*args)
end
end
Capistrano::Configuration.instance(:must_exist).load do
namespace :data do
desc "Verifies that the data version is as expected"
rake_task :verify_version => :environment, :roles => :db do
run_rake("data:verify_version")
end
end
end
Truthfully, the other reason I'm asking this instead of coding it is
it seems like this is another one of those things Rake already does,
so it's again making me wonder why not just spend the time making cap
tasks be based on Rake (ala Vlad, but without trimming cap's
functionality), but that's a much bigger topic.
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