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Re: Copying autoloads

From: Philip Kaludercic
Subject: Re: Copying autoloads
Date: Tue, 26 Jul 2022 23:00:24 +0000

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> Philip Kaludercic [2022-07-25 18:56:39] wrote:
>>         (defun get-compatibility-func (name)
>>           "Return the function NAME of a compatibility alias."
>>           (let* ((compat (intern-soft (format "compat-%s" name))))
>>             (or (symbol-function (if (fboundp name) name compat))
>>                 (error "No definition for %S could be found" name))))
> Side note: if `name` is autoloaded this will not return a "valid" value,
> in the sense that the (autoload ...) value stored in `symbol-function`
> is only usable when placed inside `name` and not elsewhere (e.g. you
> can't `funcall` it, and if you store it in another symbol, calling the
> function under that other symbol will probably fail).
> Autoloads are somewhat hackish in this sense.

Would getting rid of the `symbol-function' simplify the issue?

Here would be an updated proposal:

--8<---------------cut here---------------start------------->8---
(defun get-compatibility-func (name &optional version)
  "Return the function NAME of a compatibility alias.
If the optional argument VERSION is non-nil, it is interpreted as
a string designating from what version on the actual function may
be used, even if the function may have existed prior to that."
  ;; Compat is an ELPA package that provides compatibility code for
  ;; older versions of Emacs.  To avoid overriding or advising
  ;; existing functionality, updates to existing functions are
  ;; provided by defining a "prefixed" function, starting with
  ;; `compat-'.  The following code will attempt to return a symbol
  ;; designating NAME if it is defined (and allowed according to
  ;; VERSION), otherwise fall back to one provided by Compat.
  ;; The assumption here is that either the user is tracking a recent
  ;; enough version of Emacs to have all the necessary definition, or
  ;; they are using a core package updated from ELPA, in which case
  ;; Compat has been added as a dependency.  Otherwise an error is
  ;; signalled as early as possible.
  ;; See https://elpa.gnu.org/packages/compat.html for more details.
  (let ((compat (intern-soft (format "compat-%s" name)))
        (func (symbol-function name)))
    (cond ((and (or (null version) (version<= version emacs-version))
                (fboundp name))
          ((fboundp compat) compat)
          ((error "No definition for %S could be found" name)))))
--8<---------------cut here---------------end--------------->8---

The function could be added to compat.el too, so that any core package
that depends on ELPA can make use of it.

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