Subject: bug#59710: Wrong type argument when editing a multisession variable

From: Juanma Barranquero <[email-masked]>
Date: Wed, 30 Nov 2022 02:49:15 +0100

Package: emacs
Version: 29.0.60
Severity: normal
X-Debbugs-Cc: "Lars Ingebrigtsen" <[email-masked]>

;;; init.el
(require 'multisession)
(define-multisession-variable test-var nil "Test var" :package "test")
(setf (multisession-value test-var) t)
;;; end of init.el

emacs
M-x list-multisession-values <RET>
e

Debugger entered--Lisp error: (wrong-type-argument symbolp (intern (cdr
id)))
  multisession-edit-value(("test" . "test-var"))
  funcall-interactively(multisession-edit-value ("test" . "test-var"))
  command-execute(multisession-edit-value)

The problem comes from this change

  commit bd586121ac21e046f60f75eeb0200866c38d6f9f
  Author: Lars Ingebrigtsen <[email-masked]>
  Date:   2022-01-22 11:56:13 +0100

      Make the test for existing multisession variables more sensible

      * lisp/emacs-lisp/multisession.el (multisession-edit-value):
      Unconfuse the code.

  diff --git a/lisp/emacs-lisp/multisession.el
b/lisp/emacs-lisp/multisession.el
  index 4a293796a8..25307594c6 100644
  --- a/lisp/emacs-lisp/multisession.el
  +++ b/lisp/emacs-lisp/multisession.el
  @@ -437,8 +437,8 @@ multisession-edit-value
     (let* ((object (or
                     ;; If the multisession variable already exists, use
                     ;; it (so that we update it).
  -                  (and (boundp (intern-soft (cdr id)))
  -                       (symbol-value (intern (cdr id))))
  +                  (and (intern-soft (cdr id))
  +                       (bound-and-true-p (intern (cdr id))))
                     ;; Create a new object.
                     (make-multisession
                      :package (car id)

because `bound-and-true-p' is a macro that requires as argument a symbol,
which (intern ...) is not.

ELISP> (bound-and-true-p (intern "whatever"))
*** Eval error ***  Wrong type argument: symbolp, (intern "whatever")

so I'm afraid this change was never tested.

The fix is reverting the change, doing perhaps this

diff --git a/lisp/emacs-lisp/multisession.el
b/lisp/emacs-lisp/multisession.el
index 9d6e8c0d88..78d4137317 100644
--- a/lisp/emacs-lisp/multisession.el
+++ b/lisp/emacs-lisp/multisession.el
@@ -447,8 +447,9 @@ multisession-edit-value
   (let* ((object (or
                   ;; If the multisession variable already exists, use
                   ;; it (so that we update it).
-                  (and (intern-soft (cdr id))
-                       (bound-and-true-p (intern (cdr id))))
+                  (if-let (sym (intern-soft (cdr id)))
+                      (and (boundp sym) (symbol-value sym))
+                    nil)
                   ;; Create a new object.
                   (make-multisession
                    :package (car id)