Supporting multibib in RefTeX

[Arash Esbati]

Hi all,

based on this question[1], I had a closer look how to support multibib
package in RefTeX.  The issue is that multibib creates new macros to
read bibliography databases with \newcites.  Example:

  \documentclass{article}
  \usepackage{multibib}
  \newcites{ltex}{\TeX\ and \LaTeX\ References}

  \begin{document}
  References to the \TeX book \citeltex{Knuth:1991}
  and to Lamport’s \LaTeX\ book, which appears
  only in the references\nociteltex{Lamport:1994}.
  Finally a cite to a Postscript tutorial
  \cite{Adobe:1985}.

  \bibliographystyleltex{alpha}
  \bibliographyltex{lit}

  \renewcommand{\refname}{Postscript References}
  \bibliographystyle{plain}
  \bibliography{lit}
  \end{document}

RefTeX searchs only for one bibliography command when
`reftex-locate-bibliography-files' is invoked which is the standard with
vanilla LaTeX.

The following patch tells RefTeX that multibib also supports more than
one bibliography command.  Before I install it, are there other packages
I'm missing?

--8<---------------cut here---------------start------------->8---
-> git diff lisp/textmodes/reftex-parse.el
diff --git a/lisp/textmodes/reftex-parse.el b/lisp/textmodes/reftex-parse.el
index 016c9cf399..bae455dd4d 100644
--- a/lisp/textmodes/reftex-parse.el
+++ b/lisp/textmodes/reftex-parse.el
@@ -370,13 +370,18 @@ reftex-parse-from-file
     docstruct))

 (defun reftex-using-biblatex-p ()
-  "Return non-nil if we are using biblatex rather than bibtex."
+  "Return non-nil if we are using biblatex or other specific cite package.
+biblatex and other packages like multibib allow multiple macro
+calls to load a bibliography file.  This packages should be
+detected by this function."
   (if (boundp 'TeX-active-styles)
       ;; the sophisticated AUCTeX way
-      (member "biblatex" TeX-active-styles)
+      (or (member "biblatex" TeX-active-styles)
+          (member "multibib" TeX-active-styles))
     ;; poor-man's check...
     (save-excursion
-      (re-search-forward "^[^%\n]*?\\\\usepackage.*{biblatex}" nil t))))
+      (re-search-forward
+       "^[^%\n]*?\\\\usepackage\\(\\[[^]]*\\]\\)?{biblatex\\|multibib}" nil 
t))))

 ;;;###autoload
 (defun reftex-locate-bibliography-files (master-dir &optional files)
@@ -384,7 +389,7 @@ reftex-locate-bibliography-files
   (unless files
     (save-excursion
       (goto-char (point-min))
-      ;; when biblatex is used, multiple \bibliography or
+      ;; when biblatex or multibib are used, multiple \bibliography or
       ;; \addbibresource macros are allowed.  With plain bibtex, only
       ;; the first is used.
       (let ((using-biblatex (reftex-using-biblatex-p))
@@ -392,7 +397,7 @@ reftex-locate-bibliography-files
        (while (and again
                    (re-search-forward
                     (concat
-                     ;;           "\\(\\`\\|[\n\r]\\)[^%]*\\\\\\("
+                     ;; "\\(\\`\\|[\n\r]\\)[^%]*\\\\\\("
                      "\\(^\\)[^%\n\r]*\\\\\\("
                      (mapconcat #'identity reftex-bibliography-commands "\\|")
                      "\\)\\(\\[.+?\\]\\)?{[ \t]*\\([^}]+\\)")
@@ -415,7 +420,7 @@ reftex-locate-bibliography-files
                ;; find the file
                (reftex-locate-file x "bib" master-dir)))
            files))
-    (delq nil files)))
+    (delq nil (delete-dups files))))

 (defun reftex-replace-label-list-segment (old insert &optional entirely)
   "Replace the segment in OLD which corresponds to INSERT.
--8<---------------cut here---------------end--------------->8---

As always, any comments welcome.

Best, Arash

Footnotes:
[1]  https://lists.gnu.org/archive/html/auctex/2022-01/msg00014.html