7

If my :config section is entirely wrapped in with-eval-after-load, is that equivalent to simply specifying an :after directive? That is, can I replace this:

(use-package company-tern
  :config
  (with-eval-after-load 'company
    (add-to-list 'company-backends 'company-tern)))

with this

(use-package company-tern
  :after company
  :config
  (add-to-list 'company-backends 'company-tern))

Am I correct in my understanding that if there is other configuration that isn't inside of the with-eval-after-load then it wouldn't be useful to replace it with an :after directive since that would defer the loading of the entire package just for the subset of the configuration that depends on the feature?

I should note, in the above situation it seems simple enough to just nest company-tern's use-package under company's :config section, since they're logically related. However, my question is for the more general case where the "dependency" doesn't necessarily have a logical connection, or when there is more than one "dependency."

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  • From what I understand of use-package's semantics, an alternative (cleaner?) possibility would be to put this (add-to-list ...) line in company's :config. And if you want to defer the loading of the entire company-tern package, you could put (use-package company-tern :config (add-to-list...)) in company's :config. – T. Verron Jan 20 '16 at 8:58
  • Thank you for responding @T.Verron! I actually had a larger post/question and I split it up at the request of another user. I forgot to migrate over to this one the fact that I wanted to find a way to avoid nesting use-package inside of the :config. The reason for this doesn't apply to the example I gave, but consider other situations where there is no real logical connection other than using e.g. a function of another package, or when there is more than one such "dependencies," it wouldn't make sense to nest the package under more than one package's :config section after all. – Jorge Israel Peña Jan 20 '16 at 9:04
  • Nesting use-packages is not a proper way to handle dependencies indeed. But for situations where the second package provides additional configuration to the first one, it kinda makes sense. Someone wrote blog posts on managing a configuration using use-package (maybe it was the author of the package himself), and he made extensive use of that, for example encapsulating his configuration into "personal" packages. – T. Verron Jan 20 '16 at 9:09
  • I agree completely. I'm already doing this for example with evil-related plugins, nesting them under evil's :config. I'm looking for approaches to situations where there isn't really a logical connection. I will clarify my question for other readers. By the way, if you find and link me those posts I would really appreciate it! – Jorge Israel Peña Jan 20 '16 at 9:11
  • 2
    Here are a couple : lunaryorn.com/2015/01/06/… sachachua.com/blog/2014/12/emacs-configuration-use-package (the second contains a link to a video demonstration by the author of use-package, but I didn't watch it) Sadly, I cannot find the one post that I had in mind. – T. Verron Jan 20 '16 at 9:19
4

Yes, I believe those are equivalent. If there's additional configuration outside of with-eval-after-load, then switching to use :after should be semantically equivalent to moving them inside the with-eval-after-load form and so may change when they are executed. Whether this is a problem or not will depend on the exact configuration details.

Now, I don't know the exact details of how things are implemented, so it's possible that there's some very subtle timing issue, but at least your intuition seems to match mine here.

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