Add frozen string literal comment into generated files in rails v5.1.0

add_frozen_string_literal_comment.rb

module AddFrozenStringLiteralComment
  def add_frozen_string_literal_comment(dist)
    if File.exist?(dist) && File.extname(dist) == '.rb'
      File.open(dist, 'r') do |f|
        body = f.read

        File.open(dist, 'w') do |new_f|
          new_f.write("# frozen_string_literal: true\n" + body)
        end
      end
    end
  end
end

module GeneratorPrepend
  include AddFrozenStringLiteralComment

  def invoke!
    res = super
    add_frozen_string_literal_comment(existing_migration)
    res
  end
end

module TemplatePrepend
  include AddFrozenStringLiteralComment

  def template(source, *args, &block)
    res = super
    add_frozen_string_literal_comment(args.first)
    res
  end
end

Rails::Generators::Migration
Rails::Generators::Actions::CreateMigration.send :prepend, GeneratorPrepend
Rails::Generators::NamedBase.send :prepend, TemplatePrepend

I stuck mine in config/initializers and wrapped it in if defined?(::Rails::Generators) so that it doesn't unnecessarily load generators. Dunno if there's a better way to accomplish this.

@ta1kt0me Thank you for publishing this. It saved me the time to figure it out myself. One question: What does the Rails::Generators::Migration line do? My linter is complaining about Lint/Void: Variable Migration used in void context., but if I remove it, the generator fails. Is there a method this is calling that I could call directly?

Edit: it looks like it's triggering rails's autoload functionality. Removing it and adding this at the top of the file worked: require "rails/generators/migration"

I had to modify it slightly to work with Rails 6: https://gist.github.com/thornomad/4e2f0905e2a4a6eefbc4be5772dfd4f7

Thank you!

A simpler version of this might be

return unless defined?(::Rails::Generators)

module RailsGeneratorFrozenStringLiteralPrepend
  RUBY_EXTENSIONS = %w[.rb .rake]

  def render
    return super unless RUBY_EXTENSIONS.include? File.extname(self.destination)
    "# frozen_string_literal: true\n\n" + super
  end
end

Thor::Actions::CreateFile.prepend RailsGeneratorFrozenStringLiteralPrepend

A simpler version of this might be

return unless defined?(::Rails::Generators)

module RailsGeneratorFrozenStringLiteralPrepend
  RUBY_EXTENSIONS = %w[.rb .rake]

  def render
    return super unless RUBY_EXTENSIONS.include? File.extname(self.destination)
    "# frozen_string_literal: true\n\n" + super
  end
end

Thor::Actions::CreateFile.prepend RailsGeneratorFrozenStringLiteralPrepend

Where did you that?