Re: pkg-autoloads.el vs. pkg-loaddefs.el

[Ihor Radchenko <yantar92@posteo.net>]

Stefan Monnier via "Emacs development discussions."
<emacs-devel@gnu.org> writes:

> Here's how I see it:
>
> `<pkg>-autoloads.el` is supposed to contain what would have gone into
> `lisp/loaddefs.el` if the package were part of Emacs.  I.e. it should
> contain the strict minimum necessary to expose the usual entry points to
> the package: enough that users of the package usually don't need to do
> things like add `require` or touch `auto-mode-alist` in their `.emacs`,
> but not so much that users who *don't* use the package pay an undue cost.
> ELPA packages can be installed without ever being used, just like
> packages bundled with Emacs, and contrary to `lisp/loaddefs.el`,
> `<pkg>-autoloads.el` are loaded at startup so the larger they are, the
> slower Emacs starts up: it's really important to keep them minimal.

Makes sense.

> `<pkg>-loaddefs.el` is not "codified" in the same way, but in practice
> it contains those autoloads *internal* to a package, i.e. loaded only
> once we know the package is being used and typically used to avoid some
> undesirable toplevel `require`s inside the package's files (e.g. to
> avoid circular dependencies, or to load the different subparts of the
> package more lazily).  It's fairly normal for such files to be
> significantly larger than the corresponding `<pkg>-autoloads.el`.

Also makes sense.
However, it potentially creates a problem for packages like Org mode
that use _both_ pkg-autoloads.el and pkg-loaddefs.el.

If I understand your explanation correctly, `package-activate' only
loads org-autoloads.el when Org mode is installed from ELPA.
It means that built-in org-loaddefs.el version pre-loaded with Emacs
remains active and any changes in org-loaddefs.el in ELPA Org mode
vs. built-in Org mode are not updated.

In fact, I recently encountered a problem that is very likely caused by
Emacs retaining org-loaddefs.el from built-in Org version. I moved Org
major mode definition to a new library org-mode.el, but M-x org-mode
still insisted on loading org.el, despite new org-loaddefs.el pointing
to org-mode.el.

IMHO, for built-in packages, it seems that pkg-loaddefs _has to be
loaded_ even when the packages is installed via package.el. Otherwise,
we are going to face random breakage every time a function/macro is
relocated to another file or a new function gets autoloaded.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>