Interest in temporary with-advice functionality?

Interest in temporary with-advice functionality?

[Campbell Barton]

Hi, for the various packages I maintain I've found it's sometimes useful 
to add temporary advice to a function and I was wondering if there is 
any interest to add a macro that supports temporary advice into emacs.

While `cl-letf` can be used, advice is especially useful for it's 
:around functionality, while possible, it gets fairly verbose to use 
cl-letf to override the function in a way that supports calling the 
original.

I've been using a "with-advice" macro (see [0]).

The macros temporarily adds, then removed the advice

(with-advice (('fn :around #'fn-override))
   ;; Run's code with fn override. ...
   )

Multiple functions can be overridden at once.

(with-advice (('fn :around #'fn-override)
               ('fn-another :after #'fn-after))
   ;; Run's code with fn & fn-another override. ...
   )

I've noticed a similar macro exists in emacs but it's only used for testing.

files-tests--with-advice in ./emacs/test/lisp/files-tests.el

I was wondering if there is any interest to have this added to emacs.
If so I could make a patch to support this.

Since it can be useful to give concrete examples, here is some example 
usage [1] .. [4] (it's used 18 times across 9 packages I maintain).

[0]: 
https://codeberg.org/ideasman42/emacs-recomplete/src/commit/7a5c4c86cdbf8ba6b045d5ace466e5dcb2f10db0/recomplete.el#L74
[1]: 
https://codeberg.org/ideasman42/emacs-elisp-autofmt/src/commit/98edd8158b778ff9a0e34b5c6615523c0035f8d6/elisp-autofmt.el#L442
[2]: 
https://codeberg.org/ideasman42/emacs-undo-fu/src/commit/ea902716f39c725db1b90dbb285b44404b3bd6df/undo-fu.el#L164
[3]: 
https://codeberg.org/ideasman42/emacs-recomplete/src/commit/7a5c4c86cdbf8ba6b045d5ace466e5dcb2f10db0/recomplete.el#L240
[4]: 
https://codeberg.org/ideasman42/emacs-doc-show-inline/src/commit/cc363ed39f023642c4d8e7c91b26c802ca356fa3/doc-show-inline.el#L530

Regards,
- Campbell

Re: Interest in temporary with-advice functionality?

[Jim Porter]

On 6/17/2024 9:12 PM, Campbell Barton wrote:
> While `cl-letf` can be used, advice is especially useful for it's 
> :around functionality, while possible, it gets fairly verbose to use 
> cl-letf to override the function in a way that supports calling the 
> original.
> 
> I've been using a "with-advice" macro (see [0]).
> 
> The macros temporarily adds, then removed the advice
[snip]
> I was wondering if there is any interest to have this added to emacs.

I've done this sort of temporary-advising more than a handful of times 
(mostly in my init.el to work around various bugs on older Emacs 
versions), and would find it useful.

Re: Interest in temporary with-advice functionality?

[Michael Heerdegen via Emacs development discussions.]

Jim Porter <jporterbugs@gmail.com> writes:

> On 6/17/2024 9:12 PM, Campbell Barton wrote:
> > While `cl-letf` can be used, advice is especially useful for it's
> > :around functionality, while possible, it gets fairly verbose to use
> > cl-letf to override the function in a way that supports calling the
> > original.
> > I've been using a "with-advice" macro (see [0]).
> > The macros temporarily adds, then removed the advice
> [snip]
> > I was wondering if there is any interest to have this added to emacs.
>
> I've done this sort of temporary-advising more than a handful of times
> (mostly in my init.el to work around various bugs on older Emacs
> versions), and would find it useful.

Me too.  But OTOH it's only a tool to write down _hacks_ more
conveniently.  We don't want this in Emacs IMO.

OTOH, such a functionality can definitely be useful for advanced users.
On the third hand, my concern is that having this easily available might
drive unexperienced users into a wrong direction.

So the current state ("people who know what they are doing implement
this feature by and for themselves and will understand the downsides by
themselves) maybe is an optimum.

Michael.