bug#8897: `completion--insert-strings' clobbers user-added text properties

[Štěpán Němec]

Tags: patch

It is possible to bind `completion-annotate-function' to add custom
annotations, which is great. Unfortunately, the `face' and `mouse-face'
text properties added by such a function are then unconditionally
overwritten by `completion--insert-strings'.

In my particular case I define annotations as buttons (which display
even more detail about a completion value upon activation), so a visual
indication of clickability is very important for me.

I wonder if something like the patch below, which fixes the problem for
me, could be applied?

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index 284cbdc..11534e6 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -1003,9 +1003,12 @@ (defun completion--insert-strings (strings)
                                    'mouse-face 'highlight)
               (put-text-property (point) (progn (insert (car str)) (point))
                                  'mouse-face 'highlight)
-              (add-text-properties (point) (progn (insert (cadr str)) (point))
-                                   '(mouse-face nil
-                                               face completions-annotations)))
+              (let ((annotation (cadr str)))
+                (if (text-properties-at 1 annotation)
+                    (insert annotation)
+                  (add-text-properties (point) (progn (insert annotation) 
(point))
+                                       '(mouse-face nil
+                                                    face 
completions-annotations)))))
            (cond
             ((eq completions-format 'vertical)
              ;; Vertical format