Use lsp-mode for some projects and ggtags for others

Question

Is there a way to configure Emacs to activate lsp-mode for some projects and ggtags for other projects? Maybe using .dir-locals.el?

I code C++ and the project I most often work on doesn't support lsp-mode (I'm unable to create a working compile_commands.json because of unusual project structure). In this project I use ggtags. But when I work on other C++-projects I would like to use lsp-mode instead. But all configurations I have seen all load lsp-mode or ggtags based on prog-mode (c++-mode etc) and not on specific project.

Answer 1

Yes, you want to use .dir-locals.el and assuming the enable/disable commands you need are functions, its pseudo-variable eval. If you have lsp-mode globally enabled, add something like this to the .dir-locals.el file in the root of your "odd" project:

;;; Directory Local Variables
;;; For more information see (info "(emacs) Directory Variables")

;;; disable lsp-mode and enable ggtags-mode
((nil . ((eval . (lsp-mode -1))
         (eval . (ggtags-mode 1)))
))

(Note, I don't use either mode, so be sure you use the correct functions to disable lsp-mode and enable ggtags-mode.)

@phils has a good answer here on formatting the .dir-locals.el file.