bug#81621: 32.0.50; regression in 6223d243da3f45 - cursor moves erratically

Platon Pronko <[email protected]> writes:

> I am using lsp-mode with company-box for completions display. If
> completion popup is visible and I type characters, the position of the
> cursor jumps around, seemingly to the beginning of line or file.
>
> How to reproduce:

> If I wrap this goto-char & apply block in save-excursion, then the
> problem goes away.

I couldn't reproduce (sorry, too much setup), but I think you're right,
this was a bit sloppy, indeed.

I'll push the patch after my sig master shortly, then you can test.

João

diff --git a/lisp/progmodes/flymake.el b/lisp/progmodes/flymake.el
index 2d9ff648dce..6a36aa9845f 100644
--- a/lisp/progmodes/flymake.el
+++ b/lisp/progmodes/flymake.el
@@ -1256,13 +1256,15 @@ flymake-make-report-fn
 BACKEND is used to help Flymake distinguish different diagnostic
 sources.  If provided, TOKEN helps Flymake distinguish between
 different runs of the same backend."
-  (let ((buffer (current-buffer))
-        (point (point)))
+  (let ((buffer (current-buffer)) (p (point-marker)))
     (lambda (&rest args)
       (when (buffer-live-p buffer)
         (with-current-buffer buffer
-          (goto-char point)
-          (apply #'flymake--handle-report backend token args))))))
+          (save-excursion
+            (goto-char p)
+            (unwind-protect
+                (apply #'flymake--handle-report backend token args)
+              (set-marker p nil))))))))
 
 (defun flymake--collect (fn &optional message-prefix)
   "Collect Flymake backends matching FN.