Hi Stefan,

Thanks very much for the review. I'll try to address most of it in a
revised patch tomorrow, but I did want to explain now that the default
implementation of xref-find-references in xref.el uses semantic symref
functionality to search files. The TeX backend puts a wrapper around it,
but doesn't, following Dmitry's advice, try to reinvent that wheel. As for
where we set the filepattern variable, I don't mind, but AUCTeX is setting
it internally for their modes, so it seemed OK in tex-mode, too.

More tomorrow, and thanks again.

David.

On Sun, 9 Jun 2024, 12:36 Stefan Kangas, <stefankangas@gmail.com> wrote:

> David Fussner <dfussner@googlemail.com> writes:
>
> > In case the changeset might prove acceptable for version 30, I attach
> > the latest patch, which clears out the code I was using to simplify
> > testing of the AUCTeX modes.
>
> I have some comments and questions:
>
> - Does this need a NEWS entry?
>
> - I see the brief text you added to tex-mode.el explaining more about
>   expl3, but perhaps there should be a clear explanation in the commit
>   message too.
>
> - [Optional: In most places you use spaces for indentation, but here and
>   there, there is a single tab followed by one or more spaces.  Consider
>   using only spaces.]
>
> > From: David Fussner <dfussner@googlemail.com>
> > Date: Wed, 5 Jun 2024 10:26:18 +0100
> > Subject: [PATCH] Provide a modified xref backend for TeX buffers
>
> [Don't forget to add the bug number to the ChangeLog.]
>
> > diff --git a/doc/emacs/maintaining.texi b/doc/emacs/maintaining.texi
> > index 579098c81b1..a064103aa25 100644
> > --- a/doc/emacs/maintaining.texi
> > +++ b/doc/emacs/maintaining.texi
> > @@ -2529,6 +2529,15 @@ Identifier Search
> >  referenced.  The XREF mode commands are available in this buffer, see
> >  @ref{Xref Commands}.
> >
> > +When invoked in a buffer whose major mode uses the @code{etags} backend,
> > +@kbd{M-?} searches files and buffers whose major mode matches that of
> > +the original buffer.  It guesses that mode from file extensions, so if
> > +@kbd{M-?} seems to be skipping relevant buffers or files, try
> > +customizing either the variable @code{semantic-symref-filepattern-alist}
>
> Why does this speak of Semantic?  Does `xref-find-references` depend on
> it somehow?
>
> > diff --git a/lib-src/etags.c b/lib-src/etags.c
> > index 03bc55de03d..6bc734e7df0 100644
> > --- a/lib-src/etags.c
> > +++ b/lib-src/etags.c
> > @@ -5740,11 +5756,25 @@ Scheme_functions (FILE *inf)
> >  static linebuffer *TEX_toktab = NULL; /* Table with tag tokens */
> >
> >  /* Default set of control sequences to put into TEX_toktab.
> > -   The value of environment var TEXTAGS is prepended to this.  */
> > +   The value of environment var TEXTAGS is prepended to this.
> > +   (2024) Add variants of '\def', some additional LaTeX (and
> > +   former xparse) commands, common variants from the
> > +   'etoolbox' package, and the main expl3 commands. */
>
> Do we really need this comment?  Isn't the git log enough?
>
> > diff --git a/lisp/textmodes/tex-mode.el b/lisp/textmodes/tex-mode.el
> > index 97c950267c6..fbf08840699 100644
> > --- a/lisp/textmodes/tex-mode.el
> > +++ b/lisp/textmodes/tex-mode.el
> > @@ -636,6 +636,14 @@ tex-font-lock-keywords-2
> >             3 '(tex-font-lock-append-prop 'bold) 'append)))))
> >     "Gaudy expressions to highlight in TeX modes.")
> >
> > +(defvar-local tex-expl-region-list nil
> > +  "List of region boundaries where expl3 syntax is active.
> > +It will be nil in buffers where expl3 syntax is always active, e.g.,
>
> Please prefer "for example" to "e.g.".
>
> > +(defvar-local tex-expl-buffer-p nil
> > +  "Non-nil in buffers where expl3 syntax is always active.")
>
> What does "always active" mean as compared to just "active"?
> Does this need to be elaborated?
>
> > +;; Populate `semantic-symref-filepattern-alist' for the in-tree modes;
> > +;; AUCTeX is doing the same for its modes.
> > +(with-eval-after-load 'semantic/symref/grep
> > +  (defvar semantic-symref-filepattern-alist)
> > +  (push '(latex-mode "*.[tT]e[xX]" "*.ltx" "*.sty" "*.cl[so]"
> > +                     "*.bbl" "*.drv" "*.hva")
> > +        semantic-symref-filepattern-alist)
> > +  (push '(plain-tex-mode "*.[tT]e[xX]" "*.ins")
> > +        semantic-symref-filepattern-alist)
> > +  (push '(doctex-mode "*.dtx") semantic-symref-filepattern-alist))
>
> Doesn't this stuff rather belong in semantic itself?
>
> > +(cl-defmethod xref-backend-references ((_backend (eql 'tex-etags))
> identifier)
> > +  "Find references of IDENTIFIER in TeX buffers and files."
> > +  (require 'semantic/symref/grep)
>
> Are we sure that we want to make this depend on semantic?
>
> Is there any way around that?
>