how to override gem generator template in Rails app

Question

I know how to override a Rails template in a gem, but how can I override gem generator template in a Rails application

e.g.: https://github.com/elabs/pundit/blob/master/lib/generators/pundit/policy/templates/policy.rb

or

https://github.com/drapergem/draper/blob/master/lib/generators/rails/templates/decorator.rb

so that rails g decorator Foo would generate my template, not the gem native one

thx

Answer 1

From Rails guide on generators:

In Rails 3.0 and above, generators don't just look in the source root for templates, they also search for templates in other paths. And one of them is lib/templates.

So, if you mimic the directory hierarchy of the gem/tamplate you are trying to override, rails will pick your template instead of the ones in the gem source

Update:

Now, the question is how to correctly mimic that hierarchy so rails pick your template up?

Well it turned out there is some kind of a rule | pattern for that, for example if you want to override a template in this path: lib/generators/pundit/policy/templates/policy.rb

You should place your template in lib/templates/pundit/policy/policy.rb

To override lib/generators/rails/templates/decorator.rb

You should place your template in lib/templates/rails/decorator/decorator.rb

Update 2

It seems that the pattern is flowing: lib/templates/gem_name/generator_name/template_file_name.rb

In case of Draper gem, the gem is enforcing itself to act like native Rails generator:

/draper/lib/generators/rails/templates/decorator.rb

...so that's why we needed to use:

lib/templates/rails/generator_name/template_file_name.rb.

To override RSpec template generator of a Draper gem: lib/templates/rspec/generator_name/template_file_name.rb

...and so on