I recently had to check some custom UI5 applications for their upgradability. I feared it ‘crashing’ or not starting up to begin with but was quite surprised.
Instead it worked just fine when testing it with different future UI5 releases (from 1.38 to 1.71). All I had was a lot of deprecation error/warning messages in the browser console.
I’m not sure if we tested this properly which was via respective bootstrapping with the corresponding UI5 CDN Link as well as the UI5 build-in debug tools where you can reload the application with different UI5 versions.
Maybe such a test is insufficient and when actually upgrading the SAP system component (SAP_UI) it’ll make more trouble – when not refactoring/switching out the deprecated controls but instead ‘hard’ upgrading?
If you got any information regarding this or hints, I’d really appreciate a few sentences of guidance towards whats the 'best practice' in this scenario is.