Drupal 9 Upgrade: Patching Modules 101
Prepping for a Patch
As with all things Drupal--attention to detail is paramount. It's easy to get ahead of yourself when looking for and applying a module patch, but one of the first things you'll want to do when you find one is to ensure that the patch was built for the module version you're using. A patch is a file that applies very specific changes to an already existing file. If the existing file you have on your site (say, the info.yml file associated with a module) differs from the one the patch was created for, the patch will likely fail.