[O] Bug: org-string-display throws on image display property [9.1.9 (release_9.1.9-65-g5e4542 @ /home/blc/.local/share/emacs/27.0.50/lisp/org/)]

[Basil L. Contovounesios]

Severity: minor

0. emacs -Q
1. M-x toggle-debug-on-error RET
2. Evaluate the following:

  (require 'org)
  (org-string-display
   (propertize " " 'display '(image :type svg
                                    :file "/path/to/image.svg")))

This gives the following error backtrace:

Debugger entered--Lisp error: (wrong-type-argument sequencep t)
  #f(compiled-function (s property filter) #<bytecode 0x394179>)(t invisible 
#f(compiled-function (props) #<bytecode 0x394185>))
  #f(compiled-function (s) #<bytecode 0x11718f5>)(t)
  #f(compiled-function (props) #<bytecode 0x1171905>)((display (image :type svg 
:file "/path/to/image.svg")))
  #f(compiled-function (s property filter) #<bytecode 0x394179>)(#(" " 0 1 
(display (image :type svg :file "/path/to/image.svg"))) display 
#f(compiled-function (props) #<bytecode 0x1171905>))
  #f(compiled-function (build-from-parts prune-invisible s) #<bytecode 
0x3940dd>)(#f(compiled-function (s property filter) #<bytecode 0x394179>) 
#f(compiled-function (s) #<bytecode 0x11718f5>) #(" " 0 1 (display (image :type 
svg :file "/path/to/image.svg"))))
  org-string-display(#(" " 0 1 (display (image :type svg :file 
"/path/to/image.svg"))))
  eval((org-string-display (propertize " " 'display '(image :type svg :file 
"/path/to/image.svg"))) nil)
  elisp--eval-last-sexp(t)
  eval-last-sexp(t)
  eval-print-last-sexp(nil)
  funcall-interactively(eval-print-last-sexp nil)
  call-interactively(eval-print-last-sexp nil nil)
  command-execute(eval-print-last-sexp)

I realise that org-string-display is a relatively obscure function that
was probably not designed with image or other complex display properties
in mind, but AFAICT the following is a pretty obvious "fix", given that
the surrounding code expects 'value' to be a string or nil, but never t:

diff --git a/lisp/org/org-macs.el b/lisp/org/org-macs.el
index 583633605f..5ab069e6a2 100644
--- a/lisp/org/org-macs.el
+++ b/lisp/org/org-macs.el
@@ -108,7 +108,7 @@ org-string-display
                       ;; string (face...).
                       (let* ((display (plist-get props 'display))
                              (value (if (stringp display) display
-                                      (cl-some #'stringp display))))
+                                       (cl-find-if #'stringp display))))
                         (when value
                           (apply #'propertize
                                  ;; Displayed string could contain

With this change, the return value of org-string-display does not really
make sense for images, but at least the function doesn't barf on complex
but valid display properties.  WDYT?

Thanks,

-- 
Basil

Emacs  : GNU Emacs 27.0.50 (build 3, x86_64-pc-linux-gnu, X toolkit, Xaw3d 
scroll bars)
 of 2018-09-01
Package: Org mode version 9.1.9 (release_9.1.9-65-g5e4542 @ 
/home/blc/.local/share/emacs/27.0.50/lisp/org/)