Subject: bug#66846: 30.0.50; unexpected behavior of icon with non-existing image file?

From: David Ponce <[email-masked]>
Date: Tue, 31 Oct 2023 13:29:43 +0100

Hello,

I found a possible unexpected behavior with image in icon spec.
Here are 2 small recipes that illustrate this.  In both cases the image
doesn't exist and maybe `icon-string' should return the text value of
the icon, instead of failing like illustrated below (emacs -Q):

;; TEST 1 with relative file name.
;; Raise a wrong-type-argument error instead of inserting the text
;; "test".
(define-icon test nil
'((image "does-not-exist.svg")
   (text "test"))
  "Test icon."
  :version "30")

(insert (icon-string 'test))
Debugger entered--Lisp error: (wrong-type-argument stringp nil)
   string-match("\\.png\\'" nil nil t)
   image-supported-file-p(nil)
   ...

;; TEST 2 with absolute file name.
;; Insert an invalid image instead of the text "test".
(define-icon test1 nil
   '((image "/does-not-exist.svg")
     (text "test"))
   "Test1 icon."
   :version "30")
((button custom-icon) (test1 custom-icon))
(insert (icon-string 'test1))
  nil

Please find a possible fix in the below patch to icons.el:

diff --git a/lisp/emacs-lisp/icons.el b/lisp/emacs-lisp/icons.el
index 9a6d26243c7..dec8eaa9fac 100644
--- a/lisp/emacs-lisp/icons.el
+++ b/lisp/emacs-lisp/icons.el
@@ -188,10 +188,11 @@ icons--merge-spec
  
  (cl-defmethod icons--create ((_type (eql 'image)) icon keywords)
    (let ((file (if (file-name-absolute-p icon)
-                  icon
+                  (and (file-readable-p icon) icon)
                  (and (fboundp 'image-search-load-path)
                       (image-search-load-path icon)))))
-    (and (display-images-p)
+    (and file
+         (display-images-p)
           (fboundp 'image-supported-file-p)
           (image-supported-file-p file)
           (propertize

In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
  3.24.38, cairo version 1.17.8)
Repository revision: ecc8870981ef1a802f9504b1d0f261d19ab372b1
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12014000
System Description: Fedora Linux 38 (KDE Plasma)

Configured using:
  'configure PKG_CONFIG_PATH=/usr/local/lib/pkgconfig:/usr/lib/pkgconfig'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY
INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB

Important settings:
   value of $LC_TIME: fr_FR.utf8
   value of $LANG: fr_FR.UTF-8
   locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
   tooltip-mode: t
   global-eldoc-mode: t
   eldoc-mode: t
   show-paren-mode: t
   electric-indent-mode: t
   mouse-wheel-mode: t
   tool-bar-mode: t
   menu-bar-mode: t
   file-name-shadow-mode: t
   global-font-lock-mode: t
   font-lock-mode: t
   blink-cursor-mode: t
   minibuffer-regexp-mode: t
   line-number-mode: t
   indent-tabs-mode: t
   transient-mark-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068
epg-config gnus-util text-property-search time-date subr-x mm-decode
mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader
cl-loaddefs cl-lib sendmail rfc2047 rfc2045 ietf-drums mm-util
mail-prsvr mail-utils rmc iso-transl tooltip cconv eldoc paren electric
uniquify ediff-hook vc-hooks lisp-float-type elisp-mode mwheel
term/x-win x-win term/common-win x-dnd touch-screen tool-bar dnd fontset
image regexp-opt fringe tabulated-list replace newcomment text-mode
lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow isearch
easymenu timer select scroll-bar mouse jit-lock font-lock syntax
font-core term/tty-colors frame minibuffer nadvice seq simple cl-generic
indonesian philippine cham georgian utf-8-lang misc-lang vietnamese
tibetan thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek
romanian slovak czech european ethiopic indian cyrillic chinese
composite emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs
theme-loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads dbusbind inotify lcms2
dynamic-setting system-font-setting font-render-setting cairo gtk
x-toolkit xinput2 x multi-tty move-toolbar make-network-process emacs)

Memory information:
((conses 16 37932 10514) (symbols 48 5212 0) (strings 32 13264 1275)
  (string-bytes 1 378221) (vectors 16 10360)
  (vector-slots 8 157502 10085) (floats 8 38 21) (intervals 56 220 0)
  (buffers 992 10))