Re: Looking at function

[Dmitry Gutov]

On 12.07.2022 03:29, Stefan Monnier wrote:
> Dmitry Gutov [2022-07-12 03:19:42] wrote:
> > On 11.07.2022 22:14, Juri Linkov wrote:
> > > > > 1. Replace ‘looking-at’ with a call to the search function,
> > > > >       but keep it at point by prepending ‘\\=’ to the regexp.
> > > > >       Can it break a complex regexp?
> > > > I suppose it can. Even a simple one (that has \\| inside without
> > > > a grouping).
> > > This is what the fix for xref successfully uses in bug#53758
> > > with changes in perform-replace from bug#14013.  (However,
> > > none of these variants is suitable for replacing another call
> > > of looking-at in isearch-search-and-update.)
> > Right. Because xref basically uses literal matching, no alternations.
> > But it will break more complex cases.
> I can't see why "\\=\\(?:...\\)" would break anything, personally.

Right.

But I suppose this approach could be problematic when 
isearch-regexp-function or isearch-search-fun-function have non-default 
and some distinctly weird values/specialized behaviors.