use-package :defer t and add-hook

Question

If I have something like:

(use-package X
  :defer t
  (add-hook 'some-mode 'package-x-function))

Will that work as expected given that I set :defer t and the package doesn't have any "built-in" autoloads and I'm not using any of the autoload-creating use-package functions? In other words, does registering a hook alone take care of loading package X given that I set :defer t?

If not, what is the minimal additional configuration I require to make the hook work? Would I have to do something like :commands package-x-function?

Answer 1

I think this should do what you want:

(use-package X
  :commands package-x-function
  :init
  (add-hook 'some-mode 'package-x-function))

The :commands directive will generate an autoload for package-x-function, and the :init directive will immediately add it to the hook. Because :commands implies :defer, the package won't be loaded immediately. When the hook is run, the autoload will be looked up and the package will be loaded.

If you left off the :commands part, then you'd get a void-function error when the hook is run, because Emacs won't have a definition for package-x-function and there's no autoload to tell it how to get one.