ox-texinfo: Fix definitions containing Org markup

* lisp/ox-texinfo.el (org-texinfo--match-definition): Consider :tag
being an anonymous node with multiple markup nodes.  Convert it to
plain Texinfo beforehand, so that it is available as a plain text.
Add new optional argument INFO to be able to run Org AST for :tag ->
Texinfo text conversion.
(org-texinfo--separate-definitions): Pass INFO to
`org-texinfo--match-definition'.
* testing/lisp/test-ox-texinfo.el (test-ox-texinfo/definition): New
test case.

Reported-by: 8dcc <8dcc.git@gmail.com>
Link: https://orgmode.org/list/87wmi09tdx.fsf@gmail.com

lisp/ox-texinfo.el

@@ -643,7 +643,7 @@ Return new tree."
 	(let ((contents (org-element-contents plain-list))
 	      (items nil))
 	  (dolist (item contents)
-	    (pcase-let ((`(,cmd . ,args) (org-texinfo--match-definition item)))
+	    (pcase-let ((`(,cmd . ,args) (org-texinfo--match-definition item info)))
 	      (cond
 	       (cmd
 		(when items
@@ -659,16 +659,17 @@ Return new tree."
     info)
   tree)
 
-(defun org-texinfo--match-definition (item)
+(defun org-texinfo--match-definition (item &optional info)
   "Return a cons-cell if ITEM specifies a Texinfo definition command.
-The car is the command and the cdr is its arguments."
-  (let ((tag (car-safe (org-element-property :tag item))))
+The car is the command and the cdr is its arguments.
+INFO is the export INFO plist."
+  (let ((tag (org-export-data (org-element-property :tag item) info)))
     (and tag
 	 (stringp tag)
 	 (string-match org-texinfo--definition-command-regexp tag)
 	 (pcase-let*
 	     ((cmd (car (rassoc (match-string-no-properties 1 tag)
-				 org-texinfo--definition-command-alist)))
+				org-texinfo--definition-command-alist)))
 	      (`(,cmd ,category)
 	       (and cmd (save-match-data (split-string cmd " "))))
 	      (args (match-string-no-properties 2 tag)))

testing/lisp/test-ox-texinfo.el

@@ -443,7 +443,25 @@ body
          (and
           (re-search-forward "@defvar nil")
           (re-search-forward "Description")
-          (re-search-forward "@end defvar")))))))
+          (re-search-forward "@end defvar"))))))
+  ;; Function name containing markup
+  (should
+   (org-test-with-temp-text
+       (string-join
+        (list "- Function: ~foo_bar~ arg ::"
+              "  Description")
+        "\n")
+     (let ((export-buffer "*Test Texinfo Export*")
+           (org-export-show-temporary-export-buffer nil))
+       (org-export-to-buffer 'texinfo export-buffer
+         nil nil nil nil nil
+         #'texinfo-mode)
+       (with-current-buffer export-buffer
+         (goto-char (point-min))
+         (and
+          (re-search-forward "@defun @code{foo_bar} arg")
+          (re-search-forward "Description")
+          (re-search-forward "@end defun")))))))
 
 
 ;;; Escaping