Don't think this is one is Vector specific so made some adjustments.

I imagine this would take the shape of a PHPUnit structure test, much like the similar linters and run-time validators we have there already.

As mentioned in T283388, I would also like to go a step further and actually provide a standalone CLI command (like composer make-resource-def or some such) that generates these automatically, which is the command you'd run if something was missing, without having to figure that out manually.

This would be akin to what we already do with autoload.php in core (and generateLocalAutoload.php).

In case it's interesting, I built something like this (as in hacked together quickly), when exploring migrating Popups to packageFiles but it was done as a build step in Node.js: https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Popups/+/812973/3/build.js

A newly hired developer ran into this issue today. Unfamiliar with ResourceLoader, they understandably used a require statement and expected it to just work, so we had to explain to them how ResourceLoader works so it would be good to make this more obvious / automated.