The Retrofit provides compatibility layers for legacy Drupal code to allow run on any version of Drupal.
Retrofit is not a module. All you need to do is install the package using Composer and Retrofit is available and working!
composer require retrofit-drupal/retrofit
And that's it! 🎉
This library registers a service provider to integrate with Drupal automatically. No extra configuration is needed. Once Retrofit has been added to your Drupal code base it will automatically provide backward compatibility layers for you.
If you would like free and public support, open a Discussion. You can also join the #retrofit channel on Drupal Slack as well.
If you would like paid and private support, contact Matt Glaman directly. Opportunities for paid private support are coming.
Currently, the compatibility layers are drop-in replacements. This means you can use them in your code without any changes. Some functions are namespaced for compatibility.
Get started with Retrofit for Drupal