Re: use-package :after ??

[David Masterson]

Thanks for the followup.

Ruijie Yu via Users list for the GNU Emacs text editor
<help-gnu-emacs@gnu.org> writes:

> David Masterson <dsmasterson@gmail.com> writes:
>
>> 1. If any of the listed packages are not loaded currently, then the
>> current package will not be loaded. Period.
>> 2. #1 + "magic" will be done to ensure that, once the listed packages
>> are loaded, the current package will be (auto?) loaded.
>>
>> If #1 is correct, I do not know how the current package will ever be
>> loaded if ":after" fails.  If #2 is correct, I do not know what the
>> "magic" could be to safely do this.
>
> TL;DR: #2, see below.

I tried to write it to be skimmable. ;)

>> For instance:
>>
>> (use-package org-ac :after org)
>> (use-package org)
>
> This is what I get when I `macroexpand' the first `use-package' call
> with `use-package-always-defer' set to nil.

Which I assumed is the default and goal (defer all packages until you
need them).

> [ If `u-p-a-defer' is set to t when I `macroexpand', the
> `eval-after-load' call reduces to nil on expand-time because this
> package is not installed, nor does `package.el' know how to install it
> because I only have gnu and nongnu elpa configured. ]

Understood

> (progn
>   (defvar use-package--warning3
>     #'(lambda
>         (keyword err)
>         (let
>             ((msg
>               (format "%s/%s: %s" 'org-ac keyword
>                       (error-message-string err))))
>           (display-warning 'use-package msg :error))))
>   (condition-case-unless-debug err
>       (eval-after-load 'org
>         '(if
>              (not
>               (require 'org-ac nil t))
>              (display-warning 'use-package
>                                (format "Cannot load %s" 'org-ac)
>                                :error)))
>     (error
>      (funcall use-package--warning3 :catch err))))

Hmm.

> So, this might help you understand what is happening under the hood.
> Essentially, it will try to load org-ac, only after *all packages*
> listed in the :after section, showing a warning if loading org-ac fails.

I presume the 'if' gets more complicated and more 'eval-after-load'
calls are done if :after lists more than one item, correct?

> Keep in mind, according to the macroexpand result, that this also means
> that if you load the subpackage `org-ac' manually (via a hook, autoload,
> etc), it is not going to try to load `org' at all.  I feel that this is
> kind of strange, but maybe it has its reasons.

Hmm.

> It seems that you opted to go with setting `u-p-a-defer' to t.  And
> since you didn't mention :ensure at all, I assume you set `u-p-a-ensure'
> to t as well.

I'm looking at 'ensure'.  I currently use 'auto-update' package.

> In this case, order doesn't _really_ matter, you just need to
> `(use-package sub-pkg :after main-pkg :config your-other-configs)' on
> all your subpackages.

I thought I had.  I even had 'org' before 'org-ac' (but after
'auto-complete') in .emacs, but things weren't working right until I
hand loaded 'org-ac'.  I'll have to test this some more.

How did you do the macroexpand to debug this?  I haven't seen that
technique.  Looks interesting.

> Note, since you use `org' as an example, that you should probably
> `(use-package org)' first thing in your init.el, because otherwise
> something else is probably going to load builtin `org', and the Elpa
> `org' will complain afterwards about mismatched versions.

Yes, I ran into that.  I wound up removing the builtin manually.  I
believe org has been trying to fix this.

Thanks
-- 
David Masterson