How can I run rake with --trace within capistrano?

I want capistrano to invoke rake with --trace so I can figure out why it's failing. How do开发者_JAVA技巧 I do this? set :rake 'rake --trace' doesn't work.

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The best way I found is:

set :rake, "#{rake} --trace"

This way you don't overwrite the rake variable.

For example if you use bundler this is set before to:

"bundle exec rake"

and after to:

"bundle exec rake --trace"

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The chances are your custom tasks aren't using the rake variables, but instead hard-coding rake, here's an example:

run("rake sass:compile")

This is hard-coded, and won't care about your setting set :rake, 'rake --trace', here's the correct way:

run("#{fetch(:rake)} sass:compile")

Or, shorthand:

run("#{rake} sass:compile")

You can see this in practice in the Capistrano source code, in the one place that the default recipes actually invoke rake, in the migrations task: https://github.com/capistrano/capistrano/blob/master/lib/capistrano/recipes/deploy.rb#L387