Package: emacs;
Reported by: Alan Mackenzie <acm <at> muc.de>
Date: Wed, 15 Nov 2023 17:03:02 UTC
Severity: normal
Done: Alan Mackenzie <acm <at> muc.de>
Bug is archived. No further changes may be made.
Message #32 received at 67196 <at> debbugs.gnu.org (full text, mbox):
From: Alan Mackenzie <acm <at> muc.de> To: Eli Zaretskii <eliz <at> gnu.org>, Stefan Monnier <monnier <at> iro.umontreal.ca> Cc: 67196 <at> debbugs.gnu.org, acm <at> muc.de Subject: Re: bug#67196: M-: uses a wrong value of debug-on-error when it is nil. Date: Fri, 24 Nov 2023 20:54:45 +0000
Hello, Eli and Stefan.
On Fri, Nov 24, 2023 at 20:48:40 +0200, Eli Zaretskii wrote:
> > Date: Fri, 24 Nov 2023 17:10:47 +0000
> > Cc: Eli Zaretskii <eliz <at> gnu.org>, 67196 <at> debbugs.gnu.org
> > From: Alan Mackenzie <acm <at> muc.de>
> > Firstly, though, there is a bug in the doc string of
> > eval-expression-debug-on-error: rather than stating what the meaning of
> > the variable is, what it's for, it states the low level details of how
> > it achieves the desired effect. This is needlessly restrictive. I
> > propose changing that doc string from:
> > If non-nil set `debug-on-error' to t in `eval-expression'.
> > If nil, don't change the value of `debug-on-error'.
> > to something like:
> > Non-nil means enter debugger on an error in a call from `eval-expression'.
> > Does not apply to errors handled by `condition-case' or those
> > matched by `debug-ignored-errors'.
> > A nil value for this variable will not prevent an entry to
> > the debugger caused by other variables such as `debug-on-error'.
> First, the last two sentences above should be transposed, as the
> second one is not related to the 1st one, but the 3rd one is.
Done.
> And second, please try to reword so that the text is less complicated
> and easier to understand.
I'm perhaps a bit too close to it. Apart from the first line (for which
too much information needs squashing in), I can't really see much scope
for improvement.
> Thanks.
Anyway, here's the patch of the current state. With it, M-:
debug-on-error RET shows nil, when that is the case. M-: (foo) enters
the debugger when an error gets signalled, assuming
eval-expression-debug-on-error is t (or a suitable list), but doesn't
enter the debugger when e-e-d-o-error is nil.
There's a slight disadvantage to the approach, namely the introduction of
a new internal variable debug-from--eval-expression which is tested from
signal_or_quit. On the other hand, eval-expression itself has been
noticeably simplified.
diff --git a/lisp/simple.el b/lisp/simple.el
index 02c68912dba..e8a9a795c0b 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -1981,11 +1981,17 @@ eval-expression-print-length
:version "21.1")
(defcustom eval-expression-debug-on-error t
- "If non-nil set `debug-on-error' to t in `eval-expression'.
-If nil, don't change the value of `debug-on-error'."
+ "Non-nil means enter debugger on error on a call from `eval-expression'.
+Does not apply to errors handled by `condition-case' or those
+matched by `debug-ignored-errors'.
+Like `debug-on-error', this variable's value can also be a list,
+with the same meaning as for `debug-on-error'.
+
+A nil value for this variable will not prevent an entry to
+the debugger caused by other variables such as `debug-on-error'."
:group 'lisp
:type 'boolean
- :version "21.1")
+ :version "30.1")
(defcustom eval-expression-print-maximum-character 127
"The largest integer that will be displayed as a character.
@@ -2120,34 +2126,19 @@ eval-expression
(cons (read--expression "Eval: ")
(eval-expression-get-print-arguments current-prefix-arg)))
- (let (result)
- (if (null eval-expression-debug-on-error)
- (setq result
- (values--store-value
- (eval (let ((lexical-binding t)) (macroexpand-all exp)) t)))
- (let ((old-value (make-symbol "t")) new-value)
- ;; Bind debug-on-error to something unique so that we can
- ;; detect when evalled code changes it.
- (let ((debug-on-error old-value))
- (setq result
- (values--store-value
- (eval (let ((lexical-binding t)) (macroexpand-all exp)) t)))
- (setq new-value debug-on-error))
- ;; If evalled code has changed the value of debug-on-error,
- ;; propagate that change to the global binding.
- (unless (eq old-value new-value)
- (setq debug-on-error new-value))))
-
- (let ((print-length (unless no-truncate eval-expression-print-length))
- (print-level (unless no-truncate eval-expression-print-level))
- (eval-expression-print-maximum-character char-print-limit)
- (deactivate-mark))
- (let ((out (if insert-value (current-buffer) t)))
- (prog1
- (prin1 result out)
- (let ((str (and char-print-limit
- (eval-expression-print-format result))))
- (when str (princ str out))))))))
+ (let* ((debug-from--eval-expression eval-expression-debug-on-error)
+ (result (values--store-value
+ (eval (let ((lexical-binding t)) (macroexpand-all exp)) t)))
+ (print-length (unless no-truncate eval-expression-print-length))
+ (print-level (unless no-truncate eval-expression-print-level))
+ (eval-expression-print-maximum-character char-print-limit)
+ (deactivate-mark)
+ (out (if insert-value (current-buffer) t)))
+ (prog1
+ (prin1 result out)
+ (let ((str (and char-print-limit
+ (eval-expression-print-format result))))
+ (when str (princ str out))))))
(defun edit-and-eval-command (prompt command)
"Prompting with PROMPT, let user edit COMMAND and eval result.
diff --git a/src/eval.c b/src/eval.c
index 12e811ce264..6cadda01efb 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -2033,7 +2033,8 @@ maybe_call_debugger (Lisp_Object conditions, Lisp_Object sig, Lisp_Object data)
/* Does user want to enter debugger for this kind of error? */
&& (signal_quit_p (sig)
? debug_on_quit
- : wants_debugger (Vdebug_on_error, conditions))
+ : (wants_debugger (Vdebug_from__eval_expression, conditions)
+ || wants_debugger (Vdebug_on_error, conditions)))
&& ! skip_debugger (conditions, combined_data)
/* See commentary on definition of
`internal-when-entered-debugger'. */
@@ -4299,6 +4300,13 @@ syms_of_eval (void)
See also the variable `debug-on-quit' and `inhibit-debugger'. */);
Vdebug_on_error = Qnil;
+ DEFVAR_LISP ("debug-from--eval-expression", Vdebug_from__eval_expression,
+ doc: /* Non-nil means enter debugger if an error is signaled.
+This only applies in forms called by `eval-expression'. This variable
+has the same semantics as `debug-on-error'. It is an internal variable
+only. */);
+ Vdebug_from__eval_expression = Qnil;
+
DEFVAR_LISP ("debug-ignored-errors", Vdebug_ignored_errors,
doc: /* List of errors for which the debugger should not be called.
Each element may be a condition-name or a regexp that matches error messages.
--
Alan Mackenzie (Nuremberg, Germany).
GNU bug tracking system
Copyright (C) 1999 Darren O. Benham,
1997,2003 nCipher Corporation Ltd,
1994-97 Ian Jackson.