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bug#44864: 27.1; advice.el: ad-with-originals deprecated, but no advice
From: |
Julian Gilbey |
Subject: |
bug#44864: 27.1; advice.el: ad-with-originals deprecated, but no advice on replacement |
Date: |
Thu, 26 Nov 2020 17:09:12 +0000 |
On Thu, Nov 26, 2020 at 10:39:10AM -0500, Stefan Monnier wrote:
> > ;; Use file's local variables section to set variables in
> > ;; this buffer. (Don't just copy local variables from the
> > ;; base buffer because it may have set things locally that
> > ;; we don't want in the other modes.) We need to prevent
> > ;; `mode' being processed and re-setting the major mode.
> > ;; It all goes badly wrong if `hack-one-local-variable' is
> > ;; advised. The appropriate mechanism to get round this
> > ;; appears to be `ad-with-originals', but we don't want to
> > ;; pull in the advice package unnecessarily. `flet'-like
> > ;; mechanisms lose with advice because `fset' acts on the
> > ;; advice anyway.
> > (if (featurep 'advice)
> > (ad-with-originals (hack-one-local-variable)
> > (multi-hack-local-variables))
> > (multi-hack-local-variables))
>
> The comment doesn't explain why Dave thought that "It all goes badly
> wrong if `hack-one-local-variable' is advised", so there's not much we
> can do. AFAIK it will only go wrong with some advice, so he must have
> had some particular pieces of advice in mind.
>
> `advice.el` is deprecated anyway, so my recommendation is to remove this
> test and just call `multi-hack-local-variables` without paying attention
> to any potential advice there. If/when you bump into a problem with
> that, then we'll be able to see what should be done (the best option
> might be to change the advice itself).
Thanks Stefan!
That sounds eminently sensible. Scouring the rest of Dave's file, I
found the following comment at the beginning of the function you've
just quoted from:
(defun multi-install-mode (mode &optional chunk-fn base)
"Add MODE to the multiple major modes supported by the current buffer.
CHUNK-FN, if non-nil, is a function to select the mode of a chunk,
added to the list `multi-chunk-fns'. BASE non-nil means that this
is the base mode."
(unless (memq mode multi-indirect-buffers-alist) ; be idempotent
;; This is part of a grim hack for lossage in AUCTeX, which
;; bogusly advises `hack-one-local-variable'. This loses, due to
;; the way advice works, when we run `multi-hack-local-variables'
;; below -- there ought to be a way round this, probably with CL's
;; flet. Any subsequent use of it then fails because advice has
;; captured the now-unbound variable `late-hack'... Thus ensure
;; we've loaded the mode in advance to get any autoloads sorted
;; out. Do it generally in case other modes have similar
;; problems. [The AUCTeX stuff is in support of an undocumented
;; feature which is unnecessary and, anyway, wouldn't need advice
;; to implement. Unfortunately the maintainer seems not to
;; understand the local variables mechanism and wouldn't remove
;; this. To invoke minor modes, you should just use `mode:' in
;; `local variables'.]
And in auctex/tex.el, we have:
(defadvice hack-one-local-variable (after TeX-hack-one-local-variable-after
activate)
"Call minor mode function if minor mode variable is found."
(let ((var (ad-get-arg 0))
(val (ad-get-arg 1)))
;; Instead of checking for each mode explicitely `minor-mode-list'
;; could be used. But this may make the byte compiler pop up.
(when (memq var '(TeX-PDF-mode
TeX-source-correlate-mode TeX-interactive-mode
TeX-fold-mode LaTeX-math-mode))
(if (symbol-value val) (funcall var 1) (funcall var 0)))))
So I'm guessing that's what he's referring to.
> > But there is no advice on what to do instead.
>
> I think that's because `ad-with-originals` was used on it ;-)
Ah, that's beginning to make some sense!
Many thanks,
Julian