bug#58479: 29.0.50; [feature/noverlay] Displaced overlays in notmuch search buffers after refreshing

[Matt Armstrong <matt@rfc20.org>]

Ihor Radchenko <yantar92@posteo.net> writes:

> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>
>>> I was confused because zero-length overlays were listed by
>>> describe-text-properties before your patch above.
>>
>> That is very strange and makes me suspect there's something I'm maybe
>> misunderstanding in the code I changed.
>> Can you send a recipe that shows this difference?
>
> See the recorded video link. Basically, I just executed M-x
> describe-text-properties after (3) in my second recipe.

Ihor, I can't reproduce this second issue.  I can't see your video.
Firefox on Debian Testing can't decode it for some reason.

Based on your description I wrote this.  Please excuse any amateurish
elisp.

(with-current-buffer (get-buffer-create "*b58479-2*")
  (delete-all-overlays)
  (erase-buffer)
  (insert "Empty overlay here: --><--\n")
  (goto-char (point-min))
  (search-forward "<")
  (let* ((pos (point))
         (overlays-at `(overlays-at ,pos))
         (describe-text-properties
          `(describe-text-properties
            ,pos (current-buffer) (current-buffer))))
    (make-overlay (point) (point))
    (next-line)
    (insert (format "%S -> %S\n"
                    overlays-at (eval overlays-at)))
    (insert (format "%S follows:\n" describe-text-properties))
    (eval describe-text-properties))
  (display-buffer (current-buffer)))

On mainline, I get this buffer:

----------------------------------------------------------------------
Empty overlay here: --><--
(overlays-at 25) -> nil
(describe-text-properties 25 (current-buffer) (current-buffer)) follows:

There is an overlay here:
 From 25 to 25
----------------------------------------------------------------------

On the noverlay branch I get the same result.