So you're trying to make your YAML configuration be applied after another module, the following is what you want to use, right?
--- Name: after-multisites Before: multisites --- CMSMain: extensions: - CMSMainFilterExtension
You'd think this would make it come before, but perhaps that's for another blog post.
You flush the cache, and the following appears..
Fatal error: Based on their before & after rules two fragments both need to be before/after each other in /framework/core/manifest/ConfigManifest.php on line 373
What? Having a further look into what's going on, there doesn't seem to be anything obvious, so what's actually happening?
Well, turns out that when figuring out the before/after logic, every file and fragment within those files are considered, meaning the
rules defined in other config files may be conflicting as the
Before statement is affecting all files.
So, you just needed to be more specific;
--- Name: after-multisites Before: multisites/extensions#extensions --- CMSMain: extensions: - CMSMainFilterExtension
Don't you love a good error message.