Properly guard against incomplete Rails module definitions

[mikz]

Some parts of the code guard against undefined Rails module, but some parts do that in unsafe manner.

Good example: defined?(Rails.env) && Rails.env
Bad example: defined?(Rails) && Rails.env

There are gems (eg. rails-html-sanitizer https://github.com/rails/rails-html-sanitizer/blob/2a8fe8971b02b1b14abb6634e04af4e32b0057cd/lib/rails-html-sanitizer.rb#L10-L12), that define module Rails to extend it, but then it is incomplete and causes failures.

This change unifies accessing Rails module with proper defines? guarding against incomplete definition of the Rails module.

This pattern is already used on other places in the codebase:

• view_component/app/controllers/concerns/view_component/preview_actions.rb

  Line 81 in e63ef0e

  return {} unless defined?(Rails.root)

• view_component/app/controllers/concerns/view_component/preview_actions.rb

  Line 98 in e63ef0e

  prepend_view_path Rails.root.join("app/views") if defined?(Rails.root)

• view_component/lib/view_component/engine.rb

  Line 22 in e63ef0e

  options.previews.paths << "#{Rails.root}/test/components/previews" if defined?(Rails.root) && Dir.exist?(

• view_component/lib/view_component/preview.rb

  Line 7 in e63ef0e

  if defined?(Rails.application.routes.url_helpers)

• view_component/lib/view_component/template.rb

  Line 150 in e63ef0e

  short_identifier = defined?(Rails.root) ? @path.sub("#{Rails.root}/", "") : @path

What are you trying to accomplish?

Use view_component gem without Rails.

What approach did you choose and why?

Guard clause defined? checking the nested access into the Rails module. Since it is already used within the codebase on other places.

Anything you want to highlight for special attention from reviewers?

I don't know what would be a good way to test this. A part of test suite that runs without Rails? Is that something you'd like to guarantee as a project?