Couldn't find assets.car

Using the latest Catalina Beta, I’m now seeing a fault message in console:

CoreUI: RunTimThemeRefForBundleIdentifierAndName() couldn't find Assets.car in bundle with identifier: 'com.mycompany.myapp'

Everying seems to work normally, though.

googling this error seems to find info about iOS apps, but this is a macOS app. Weird.

Edit: A closer look shows hundreds or thousands of these messages, not having anything to do with my Xojo app. So maybe just a Catalina bug?

Maybe the framework assumes that every Mac app has an Assets.car file included nowadays as Xcode builds such a file.
But Xojo apps don’t have it by default.

Xojo could certainly build one - at least on macOS
It might require installing Xcode to have the actool command line tool
And that would preclude anyone building macOS apps on other platforms as the CAR file format is not very well documented so creating one on Windows or Linux could be problematic

While at Xojo I only ever found a handful of moderately useful references
https://blog.timac.org/2018/1018-reverse-engineering-the-car-file-format/
https://github.com/insidegui/AssetCatalogTinkerer
https://github.com/alexzielenski/ThemeEngine

Much seems to rely on non-public apis and CUICatalog of the CoreUI framework

https://stackoverflow.com/questions/22630418/analysing-assets-car-file-in-ios

Thanks - since I’m seeing the error with all sorts of bundles (Apple’s own) this is probably a “wait and see” thing right now.
[I had been filtering the Console.app on the name of my app, so I hadn’t seen the errors for other apps].

if you have Xcode installed you could generate & insert an empty assets.car file and place it in your app bundle

man actool in terminal will give you a decent help page