bug#53749: 29.0.50; [PATCH] Xref backend for TeX buffers

[David Fussner via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Thanks for the reply, Arash.

> I'm not familiar with the way xref works, but reading the above, xref
> doesn't care about modes set per file variables, is this correct?

As far as I know, the default xref-find-references deals strictly in
file extensions.

> I think this is almost impossible.  Besides the effort, take for example
> the .cnf extension which is used by other programs as well, so
> associating it with LaTeX-mode wouldn't make sense, IMO.

Agreed -- this may be an argument against my current approach. I hope,
however, that the way xref-find-references searches by directory or by
project should limit spurious searching when a more common extension
appears on a TeX file.

> This is possibly the next mess since .tex can be plain-TeX, ConTeXt,
> LaTeX ...

I guess currently I'm thinking that this is sort of a feature, as
searching for symbols in files/buffers from many closely-related modes
may produce useful matches. The code I'm finishing up tends to search
more files rather than fewer, but it should be possible to prune this
if it's deemed too messy.

> So in general, I second what Stefan M. wrote in his other
> message, but respecting/using file local variables could help here.

Currently, the code takes into account file-local variables only by
including in the search list extensions of TeX-related buffers, which
may well only have become TeX-related due to such variables.

I'll post a patch as soon as I solve an outstanding issue or two, and
we'll see where we are.

Thank you indeed for your help,

David.

On Tue, 23 Apr 2024 at 13:04, Arash Esbati <arash@gnu.org> wrote:
>
> David Fussner <dfussner@googlemail.com> writes:
>
> > Thanks for the nudge. I am in fact in the final stages of preparing a
> > new patch to get xref working in TeX buffers.
>
> Thanks for the update.
>
> > The semantic/symref backend used by xref-find-references greps in
> > files matching the major-mode of the buffer where the user calls the
> > command. It looks in semantic-symref-filepattern-alist for
> > file-extensions matching the major-mode, and if that fails it looks in
> > auto-mode-alist. When both fail to produce any file extensions it
> > tells the user to customize semantic-symref-filepattern-alist. Also,
> > if it finds things in s-s-f-a, it doesn't go on to auto-mode-alist, so
> > s-s-f-a has to be complete in order to be useful. In effect, we need
> > s-s-f-a to hold all the extensions for all the modes that can appear
> > as values of major-mode, and I notice that AUCTeX has started to
> > populate that alist, though incompletely.
>
> I'm not familiar with the way xref works, but reading the above, xref
> doesn't care about modes set per file variables, is this correct?
>
> > I'm also aware that many packages add their own extensions to files
> > which are basically TeX or LaTeX files, and I wonder whether we can
> > really keep up with the whole of CTAN in terms of providing complete
> > lists of extensions for s-s-f-a.
>
> I think this is almost impossible.  Besides the effort, take for example
> the .cnf extension which is used by other programs as well, so
> associating it with LaTeX-mode wouldn't make sense, IMO.  Finally, I
> think many packages are written in .dtx format and the ones with many
> files with different extensions (.def, .enc, .fd, ...) usually extract
> them from the .dtx via an .ins file, so the edited source is inside the
> .dtx, and we don't need to care about these extensions.
>
> > As an example of where we are, if you open a plain-tex-mode (or
> > plain-TeX-mode) file and M-? with point on some standard word you'll
> > currently get the message to customize s-s-f-a, because
> > auto-mode-alist has only tex-mode and s-s-f-a doesn't cover them,
> > either.
>
> This is possibly the next mess since .tex can be plain-TeX, ConTeXt,
> LaTeX ...  So in general, I second what Stefan M. wrote in his other
> message, but respecting/using file local variables could help here (if
> it doesn't work ATM, see above), e.g.:
>
> --8<---------------cut here---------------start------------->8---
> \beginsection 1. Introduction.
> This is the start of the introduction.
> \bye
>
> %%% Local Variables:
> %%% mode: plain-TeX
> %%% TeX-master: t
> %%% End:
> --8<---------------cut here---------------end--------------->8---
>
> HTH.  Best, Arash