Prioritize app assets over engine assets

[brunoprietog]

Make the app assets always have priority when resolving them, if there is another asset with the same name in a gem. For example:

bin/importmap pin trix

You would have a vendor/javascript/trix.js file. If you call "trix" from importmap, it would still take the one from Action Text gem instead. Not anymore.

[theodorton]

Not anymore.

Are you seeing a regression compared to sprockets after migrating to propshaft?

I think we need to consider warning users in cases of ambiguous asset names, and also be clear/explicit in the documentation and configuration about load order.

Is the specific engine you're using provided from a public gem?

[dhh]

We had a regression in our app where we had a vendored trix.js that was newer than the trix.js that came with Action Text. The app should always win over any engine. I'm almost certain this is how Sprockets worked as well, since that's the only way you could have a generic engine with views that are overwritten in the app.