:preface, :config and :init?Where possible, it is better to avoid :preface, :config
and :init. Instead, prefer autoloading keywords such as
:bind (see Key bindings), :hook (see Hooks), and
:mode (see Modes and interpreters), as they will take care
of setting up autoloads for you without any need for boilerplate code.
For example, consider the following declaration:
(use-package foo :init (add-hook 'some-hook 'foo-mode))
This has two problems. First, it will unconditionally load the
package ‘foo’ on startup, which will make things slower. You can
fix this by adding :defer t:
(use-package foo :defer t :init (add-hook 'some-hook 'foo-mode))
This is better, as ‘foo’ is now only loaded when it is actually needed (that is, when the hook ‘some-hook’ is run).
The second problem is that there is a lot of boilerplate that you have
to write. In this case, it might not be so bad, but avoiding that was
what use-package was made to allow. The better option in this case is
therefore to use :hook (see Hooks), which also implies
:defer t. The above is thereby reduced down to:
(use-package foo :hook some-hook)
Now use-package will set up autoloading for you, and your Emacs startup time will not suffer one bit.