component_template.rb

component_name = Rails.root.to_s.split("/")[-3]
component_root = Rails.root.to_s.gsub("spec/dummy", "")

gemspec = <<-EOS
  s.add_development_dependency \"rspec-rails\"

  s.test_files = Dir["spec/**/*"]
EOS

inject_into_file "#{component_root}/#{component_name}.gemspec", 
                 gemspec,
                 after: "s.add_development_dependency \"sqlite3\"\n"


engine_config = <<-EOS

    config.autoload_paths += Dir["#{config.root}/lib/**/"]
    
    config.generators do |g|
      g.test_framework :rspec, fixture: false
      g.fixture_replacement :factory_girl, dir: 'spec/factories'
    end

    initializer :append_migrations do |app|
      unless app.root.to_s.match root.to_s
        config.paths["db/migrate"].expanded.each do |expanded_path|
          app.config.paths["db/migrate"] << expanded_path
        end
      end
    end
EOS

inject_into_file "#{component_root}/lib/#{component_name}/engine.rb",
                 engine_config,
                 after: "isolate_namespace #{component_name.camelize}"


run "bundle install"

new_component

#!/bin/bash
rails plugin new ./components/$@ --mountable -T --dummy-path=spec/dummy
cd ./components/$@
bundle exec rake app:rails:template LOCATION=../component_template.rb

Thanks for sharing Ben, I could be misreading your template but wouldn't you need to escape the interpolation on line 17?

config.autoload_paths += Dir["#{config.root}/lib/**/"]

to (or similar)

config.autoload_paths += Dir["\#{config.root}/lib/**/"]