use-package: Can :after be used instead of with-eval-after-load?

Question

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."

Answer 1

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.