There is a programmatical way to detect Zeitwerk::NameError when upgrading to Rails 6?

Question

I am currently migrating an old Rails application to Rails 6.

It seems that some files in the project are not consistent with the classes defined in it. I don't see this error when running the tests of the application, but after deploy I receive errors like:

 Zeitwerk::NameError: expected file /app/my?_/app/lib/multi_io.rb to define constant MultiIo, but didn't

In previous SO questions I could find suggestions to:

• Rails 6: Zeitwerk::NameError doesn't load class from module set config.autoloader = :classic
• How to ignore a folder in Zeitwerk for Rails 6? ignore a given path
• Autoloading and Zeitwerk Mode in Rails 6 tweak config.autoload_path

I am not looking for a workaround so I corrected the file raising the exception.

I would like to find a programmatical way to detect all inconsistent path/class names without running the application in production mode.

So far, three options came to my mind:

1. A rake task to validate the autoloading (which is not provided by the gem). Does it exists? Would you have a snippet to run from the rails console in development env instead?
2. A rubocop cop or another static code analyser. There is any?
3. Force the eager load in the test environment

What it the suggested approach to validate my code without requiring several iterations/deployments?

thank you very much in advance

Answer 1

You can check the autoload compatibility of a project with the zeitwerk::check task:

$ bin/rails zeitwerk:check
Hold on, I am eager loading the application.
All is good!

It exercises all the autoload paths and will flag issues such as those caused by the change in constant name inference (such as those with acronyms). The task doesn't appear to be widely advertised or documented except in the upgrade guide. But, I actually use it sometimes to just flush out constant naming issues in the project generally (i.e., where the class doesn't match the file).