; Merge from master.

1 files changed, 22 insertions, 5 deletions

diff --git a/lisp/emacs-lisp/debug.el b/lisp/emacs-lisp/debug.el
index 46b0306d64f..6c172d6c31d 100644
--- a/lisp/emacs-lisp/debug.el
+++ b/lisp/emacs-lisp/debug.el
@@ -90,6 +90,11 @@ The value used here is passed to `quit-restore-window'."
   :group 'debugger
   :version "24.3")
 
+(defcustom debug-allow-recursive-debug nil
+  "If non-nil, erroring in debug and edebug won't recursively debug."
+  :type 'boolean
+  :version "29.1")
+
 (defvar debugger-step-after-exit nil
   "Non-nil means \"single-step\" after the debugger exits.")
 
@@ -534,11 +539,23 @@ The environment used is the one when entering the activation frame at point."
                       (error 0)))) ;; If on first line.
 	(base (debugger--backtrace-base)))
     (debugger-env-macro
-      (let ((val (backtrace-eval exp nframe base)))
-        (prog1
-            (debugger--print val t)
-          (let ((str (eval-expression-print-format val)))
-            (if str (princ str t))))))))
+      (let* ((errored nil)
+             (val (if debug-allow-recursive-debug
+                      (backtrace-eval exp nframe base)
+                    (condition-case err
+                        (backtrace-eval exp nframe base)
+                      (error (setq errored
+                                   (format "%s: %s"
+                                           (get (car err) 'error-message)
+			                   (car (cdr err)))))))))
+        (if errored
+            (progn
+              (message "Error: %s" errored)
+              nil)
+          (prog1
+              (debugger--print val t)
+            (let ((str (eval-expression-print-format val)))
+              (if str (princ str t)))))))))
 
 (define-obsolete-function-alias 'debugger-toggle-locals
   'backtrace-toggle-locals "28.1")