Subject: bug#64516: [PATCH] docview: Only enable imenu when supported

From: Tassilo Horn <[email-masked]>
Date: Sat, 15 Jul 2023 20:39:20 +0200

Eli Zaretskii <[email-masked]> writes:

Hi Morgan & Eli,

>> Anyways here is a patch that unconditionally enables imenu but checks
>> the return value of mutool and will raise an imenu-unavailable-error
>> when it is not successful.  However, that error stops docview from
>> displaying the document so I decided to put the setup function in a
>> hook so the error occurs after the document is displayed.
>
> Tassilo, is this okay, in your opinion?

Yes, almost.  I'd rather handle the error rather putting the setup
function in a hook and let the error hit top-level and flash the screen.

--8<---------------cut here---------------start------------->8---
1 file changed, 11 insertions(+), 5 deletions(-)
lisp/doc-view.el | 16 +++++++++++-----

modified   lisp/doc-view.el
@@ -147,6 +147,8 @@
 (require 'filenotify)
 (eval-when-compile (require 'subr-x))
 
+(autoload 'imenu-unavailable-error "imenu")
+
 ;;;; Customization Options
 
 (defgroup doc-view nil
@@ -214,7 +216,7 @@ doc-view-mupdf-use-svg
   :type 'boolean
   :version "30.1")
 
-(defcustom doc-view-imenu-enabled (and (executable-find "mutool") t)
+(defcustom doc-view-imenu-enabled (executable-find "mutool")
   "Whether to generate an imenu outline when \"mutool\" is available."
   :type 'boolean
   :version "29.1")
@@ -1910,9 +1912,10 @@ doc-view--pdf-outline
   (let ((fn (or file-name (buffer-file-name))))
     (when fn
       (let ((outline nil)
-            (fn (shell-quote-argument (expand-file-name fn))))
+            (fn (expand-file-name fn)))
         (with-temp-buffer
-          (insert (shell-command-to-string (format "mutool show %s outline" fn)))
+          (unless (= 0 (call-process "mutool" nil (current-buffer) nil "show" fn "outline"))
+            (imenu-unavailable-error "Unable to create imenu index using `mutool'"))
           (goto-char (point-min))
           (while (re-search-forward doc-view--outline-rx nil t)
             (push `((level . ,(length (match-string 1)))
@@ -1961,7 +1964,7 @@ doc-view-imenu-index
 
 (defun doc-view-imenu-setup ()
   "Set up local state in the current buffer for imenu, if needed."
-  (when (and doc-view-imenu-enabled (executable-find "mutool"))
+  (when doc-view-imenu-enabled
     (setq-local imenu-create-index-function #'doc-view-imenu-index
                 imenu-submenus-on-top nil
                 imenu-sort-function nil
@@ -2236,7 +2239,10 @@ doc-view-mode
     (setq mode-name "DocView"
 	  buffer-read-only t
 	  major-mode 'doc-view-mode)
-    (doc-view-imenu-setup)
+    (condition-case imenu-error
+        (doc-view-imenu-setup)
+      (imenu-unavailable (message "imenu support unavailable: %s"
+                                  (cadr imenu-error))))
     (doc-view-initiate-display)
     ;; Switch off view-mode explicitly, because doc-view-mode is the
     ;; canonical view mode for PDF/PS/DVI files.  This could be
--8<---------------cut here---------------end--------------->8---

Bye,
Tassilo