How to change source for a custom rails generator? (Thor)

Question

I\'m making a custom generator that generates a new rails app, and I do it like this

require \'thor\'
require \'rails/generators/rails/app/app_generator\'

c         


        

Answer 1

The source_paths method doesn't work when using AppBuilder. (which is another option to using rails templates). I have a files directory next to the app_builder.rb file that this class is in. I have this working, though it seems there should still be a more elegant way.

tree .
|-- app_builder.rb
|-- files
     `-- Gemfile

class AppBuilder < Rails::AppBuilder

  def initialize generator
    super generator
    path = File.expand_path( File.join( '..', File.dirname( __FILE__ )) )
    source_paths << path
  end

  def gemfile
    copy_file 'files/Gemfile', 'Gemfile'
  end

and then on the console:

rails new my_app -b path_to_app_builder.rb

The dots are required since the ruby file 'app_builder.rb' is slurped up and eval'd after the rails new command changes into the new app directory (I think).

Answer 2

It's an old post, however, the problem remains the same, I spent time to figure that out. I let a comment here if it can help.

Rails add by default the path lib/templates so you can custom any templates by copying them in this directory.

Check out the correct directories structures https://github.com/rails/rails/tree/v6.0.1/railties/lib/rails/generators/rails

There is subtle though and is not so obvious to catch.

Take for instance the helper generator, as mentioned in the official Rails documentation, the structure is

https://github.com/rails/rails/tree/v6.0.1/railties/lib/rails/generators/rails/helper

- helper
  - templates
    - helper.rb.tt
  - helper_generator.rb 

Here, what Railties expects to find in your project:

- lib
  - templates 
    - helper
      - helper.rb

your helper.rb is a copy of helper.rb.tt

the last thing, if you plan to use it in Rails::Engine you have to tell it to load that path

# lib/blorgh/engine.rb 
module Blorgh
  class Engine < ::Rails::Engine
    isolate_namespace Blorgh
    config.generators.templates << File.expand_path('../templates', __dir__)
  end
end

Really hope that can help and save time for others.

1. https://github.com/rails/rails/blob/v6.0.1/railties/lib/rails/application/configuration.rb#L188
2. https://guides.rubyonrails.org/generators.html#customizing-your-workflow-by-changing-generators-templates
3. https://github.com/rails/rails/blob/v6.0.1/railties/CHANGELOG.md
4. https://guides.rubyonrails.org/engines.html

Answer 3

This worked:

require 'thor'
require 'rails/generators/rails/app/app_generator'

module Thor::Actions
  def source_paths
    [MY_TEMPLATES]
  end
end

class AppBuilder < Rails::AppBuilder
  ...
end

I don't understand why, but I've spent too much time on this already, so I don't care.

Answer 4

Thor will access your source_paths method and add these to the defaults:

  # Returns the source paths in the following order:
  #
  #   1) This class source paths
  #   2) Source root
  #   3) Parents source paths
  #
  def source_paths_for_search
    paths = []
    paths += self.source_paths
    paths << self.source_root if self.source_root
    paths += from_superclass(:source_paths, [])
    paths
  end

So all you need to do in your class is:

class NewgemGenerator < Thor::Group

  include Thor::Actions

  def source_paths
    ['/whatever', './templates']
  end

end

Hope this helps :)