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.

score 95 · Answer 1 · answered Apr 27 '13 at 21:41

95

I know this is an old question, but in any case:

rake -W

This was introduced in rake 0.9.0.

http://rake.rubyforge.org/doc/release_notes/rake-0_9_0_rdoc.html

Support for the –where (-W) flag for showing where a task is defined.

answered Apr 27 '13 at 21:41

Magne Land

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Thanks for updating this, always nice to get a more current answer! – Matt Sanders Aug 26 '13 at 19:11
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Wow, why I didn't know it earlier! Thank you! – Ruslan Valeev Oct 15 '20 at 02:39

Tom Lubitz · Accepted Answer · 2015-08-01T00:02:25.807

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Despite what others have said, you can programmatically get the source location of rake tasks in a rails application. To do this, just run something like the following in your code or from a console:

# load all the tasks associated with the rails app
Rails.application.load_tasks

# get the source locations of actions called by a task
task_name = 'db:schema:load' # fully scoped task name
Rake.application[task_name].actions.map(&:source_location)

This will return the source locations of any code that gets executed for this task. You can also use #prerequisites instead of #source_location to get a list of prerequisite task names (e.g. 'environment', etc).

You can also list all tasks loaded using:

Rake.application.tasks

UPDATE: See Magne's good answer below. For versions of rake >= 0.9.0 you can use rake -W to show the source location of your rake tasks.

edited Aug 01 '15 at 00:02

answered Apr 12 '12 at 18:50

Tom Lubitz

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Just FYI: you have to make sure that rake is loaded before you use this method. if it is not, simply do a "require 'rake'". – Tom Lubitz Aug 27 '13 at 18:15
much obliged, kind sir! – mrstif May 05 '15 at 18:01
Nice man! You remember how did you find it out? I was getting stuck inside rake itself for task `assets:environment`, which thanks to your solution now I know resides in `railties-5.0.0.1/lib/rails/application.rb:445`. The `rake -W` was a dead end. – medik Feb 27 '18 at 16:01

Bob Aman · Answer 3 · 2009-05-06T18:04:52.130

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. :-)

score 0 · Answer 4 · answered May 06 '09 at 16:37

0

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.

answered May 06 '09 at 16:37

Mike Woodhouse

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But is there a programmatic way to do this? I ended up doing a find in file search. – Tilendor May 06 '09 at 16:49

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

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