diff --git a/modules/ui/popup/autoload/popup.el b/modules/ui/popup/autoload/popup.el
index d12a44e62..b034c1ae8 100644
--- a/modules/ui/popup/autoload/popup.el
+++ b/modules/ui/popup/autoload/popup.el
@@ -390,6 +390,18 @@ the message buffer in a popup window."
     (+popup/close window 'force)
     (display-buffer-pop-up-window buffer nil)))
 
+;;;###autoload
+(defun +popup/diagnose ()
+  "Reveal what popup rule will be used for the current buffer."
+  (interactive)
+  (or (cl-loop with bname = (buffer-name)
+               for (pred . action) in display-buffer-alist
+               if (and (functionp pred) (funcall pred bname action))
+               return (cons pred action)
+               else if (and (stringp pred) (string-match-p pred bname))
+               return (cons pred action))
+      (message "No popup rule for this buffer")))
+
 
 ;;
 ;; Advice