A small gripe, but one which gets me every time.
I use vscode with some auto-generated source files which are marked on disk as read-only. Because the auto-generated files appear similar to the normal source files in my project, I start to edit them and only discover when I try to save that I'm in the wrong file.

As well as #17621, it would be really useful to have a configurable editor option that prevents any editing of read-only files. Any keystrokes, pasting, etc are simply ignored.