bug#66326: 29.1.50; There should be a way to promote warnings to errors

[Spencer Baugh]

Eli Zaretskii <eliz@gnu.org> writes:
> And in this case, duplication is a lesser evil than reordering of
> logic, since the chances of unintended consequences would be lower in
> the former case.

OK, how about this version then?

>From 11fdd0cdd2d0da28848ad42d8087ebb1a4e05430 Mon Sep 17 00:00:00 2001
From: Spencer Baugh <sbaugh@janestreet.com>
Date: Tue, 3 Oct 2023 14:36:25 -0400
Subject: [PATCH] Support turning warnings into errors

Support turning warnings into errors in a user-configurable way.  This
is especially useful in combination with (setq debug-on-error t) to
drop to the debugger when a warning happens.

* lisp/emacs-lisp/warnings.el (warning-suppress-types): Improve
docstring.
(warning-to-error-types, warning-to-error): Add.
(display-warning): Check warning-to-error-types.
---
 lisp/emacs-lisp/warnings.el | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/lisp/emacs-lisp/warnings.el b/lisp/emacs-lisp/warnings.el
index 31b840d6c83..0e8464c4455 100644
--- a/lisp/emacs-lisp/warnings.el
+++ b/lisp/emacs-lisp/warnings.el
@@ -114,11 +114,20 @@ warning-suppress-types
 The element must match an initial segment of the list TYPE.
 Thus, (foo bar) as an element matches (foo bar)
 or (foo bar ANYTHING...) as TYPE.
+An empty list as an element matches any TYPE.
 If TYPE is a symbol FOO, that is equivalent to the list (FOO),
 so only the element (FOO) will match it.
 See also `warning-suppress-log-types'."
   :type '(repeat (repeat symbol))
   :version "22.1")
+
+(defcustom warning-to-error-types nil
+  "List of warning types to signal as an error instead.
+If any element of this list matches the TYPE argument to `display-warning',
+`display-warning' signals an error instead of logging a warning.
+See `warning-suppress-types' for the format of elements in this list."
+  :type '(repeat (repeat symbol))
+  :version "30.1")
 
 ;; The autoload cookie is so that programs can bind this variable
 ;; safely, testing the existing value, before they call one of the
@@ -230,6 +239,14 @@ warnings-suppress
                               (cons (list type) warning-suppress-types)))
     (_ (message "Exiting"))))
 
+(defun warning-to-error (type message level)
+  (unless level
+    (setq level :warning))
+  (let* ((typename (if (consp type) (car type) type))
+         (level-info (assq level warning-levels)))
+    (error (nth 1 level-info)
+           (format warning-type-format typename))))
+
 ;;;###autoload
 (defun display-warning (type message &optional level buffer-name)
   "Display a warning message, MESSAGE.
@@ -263,6 +280,11 @@ display-warning
 disable automatic display of the warning or disable the warning
 entirely by setting `warning-suppress-types' or
 `warning-suppress-log-types' on their behalf."
+  (when (and (> (warning-numeric-level (or level :warning))
+               (warning-numeric-level warning-minimum-log-level))
+            (not (warning-suppress-p type warning-suppress-log-types))
+             (warning-suppress-p type warning-to-error-types))
+    (warning-to-error type message level))
   (if (not (or after-init-time noninteractive (daemonp)))
       ;; Ensure warnings that happen early in the startup sequence
       ;; are visible when startup completes (bug#20792).
-- 
2.39.3