() Stefan Monnier <monnier@iro.umontreal.ca>
() Sat, 24 Dec 2016 00:02:03 -0500

   To the extent that it affects the end-user and is caught
   during execution, this mechanism needs to be very careful not
   to get in the way, although it should be visible enough that
   we can reasonably expect that the user will likely see those
   messages.

Here's an idea:

(defun message-with-properties (plist fmt &rest args)
  "Like ‘message’ for FMT and ARGS, and also propertize w/ PLIST.
Return the propertized, formatted string."
  (with-current-buffer (get-buffer "*Messages*")
    (let* ((beg (goto-char (point-max)))
           (str (apply #'message fmt args))
           (end (+ beg (length str) 1))
           (inhibit-read-only t))
      (add-text-properties beg end plist)
      (buffer-substring beg end))))

(message-with-properties
 '(face font-lock-warning-face)
 "obsolete: %S" 'obsolete-thing)

We can then tell people to look for easily visible "obsolete" in
*Messages*, and they can do that at their own convenience, or we
can programmatically collect such blurbs for a more concentrated
presentation, later.  In the meantime, this can be tweaked a bit
for other (ab)uses, such as ‘C-u C-h e’ doing filtering based on
various properties, etc.  WDYT?

-- 
Thien-Thi Nguyen -----------------------------------------------
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     (`(technical mailing-list) t)
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