How do I find the source file for a rake task?

Question

I know you can view all possible rake tasks by typing

rake -T

But I need to know what exactly a task does. From the output, how can I find a source file that actually has the task? For example, I'm trying to find the source for the db:schema:dump task.

Answer 1

For most rake tasks in Rails, look in the Rails gem directory, in lib/tasks.

If you've vendored Rails into your app directory structure then look in vendor/rails/railties/lib/tasks instead

Either way, db:schema:dump is in databases.rake.

Answer 2

There is no programmatic way to do this unfortunately. Rake tasks can be loaded either from rails itself, lib/tasks, or from any plugin with a tasks directory.

This should nab most everything not within Rails itself:

find . -name "*.rake" | xargs grep "whatever"

As for db:schema:dump, here's the source:

desc "Create a db/schema.rb file that can be portably used against any DB supported by AR"
task :dump => :environment do
  require 'active_record/schema_dumper'
  File.open(ENV['SCHEMA'] || "#{RAILS_ROOT}/db/schema.rb", "w") do |file|
    ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, file)
  end
end

It can be found on line 242 of lib/tasks/database.rake in the rails 2.2.2 gem. If you've got a different version of Rails, just search for "namespace :schema".

You probably actually want the source of the ActiveRecord::SchemaDumper, but I think you should have no trouble figuring out where that is. :-)