Make erc--server-reconnecting non-buffer-local

* lisp/erc/erc-backend.el (erc--server-reconnecting): Mention expected
non-nil value type in doc string.
(erc-server-connect): Don't set `erc--server-reconnecting'.
(erc-server--reconnect): Let-bind `erc--server-reconnecting' instead
of setting it locally in the server buffer.  Set it to an alist
containing the current buffer's local variables.
(erc-process-sentinel-2): Don't set `erc--server-reconnect'.
* lisp/erc/erc.el (erc--cmd-reconnect): Clean up some assertions.
(Bug#57955.)

2 files changed, 12 insertions, 11 deletions

diff --git a/lisp/erc/erc-backend.el b/lisp/erc/erc-backend.el
index f899b866f04..30b53dfd8ed 100644
--- a/lisp/erc/erc-backend.el
+++ b/lisp/erc/erc-backend.el
@@ -311,8 +311,13 @@ current IRC process is still alive.")
 (make-obsolete-variable 'erc-server-reconnecting
                         "see `erc--server-reconnecting'" "29.1")
 
-(defvar-local erc--server-reconnecting nil
-  "Non-nil when reconnecting.")
+(defvar erc--server-reconnecting nil
+  "An alist of buffer-local vars and their values when reconnecting.
+This is for the benefit of local modules and `erc-mode-hook'
+members so they can access buffer-local data from the previous
+session when reconnecting.  Once `erc-reuse-buffers' is retired
+and fully removed, modules can switch to leveraging the
+`permanent-local' property instead.")
 
 (defvar-local erc-server-timed-out nil
   "Non-nil if the IRC server failed to respond to a ping.")
@@ -664,7 +669,6 @@ TLS (see `erc-session-client-certificate' for more details)."
       (setq erc-server-process process)
       (setq erc-server-quitting nil)
       (setq erc-server-reconnecting nil
-            erc--server-reconnecting nil
             erc--server-reconnect-timer nil)
       (setq erc-server-timed-out nil)
       (setq erc-server-banned nil)
@@ -706,11 +710,11 @@ Make sure you are in an ERC buffer when running this."
     (with-current-buffer buffer
       (erc-update-mode-line)
       (erc-set-active-buffer (current-buffer))
-      (setq erc--server-reconnecting t)
       (setq erc-server-last-sent-time 0)
       (setq erc-server-lines-sent 0)
       (let ((erc-server-connect-function (or erc-session-connector
-                                             #'erc-open-network-stream)))
+                                             #'erc-open-network-stream))
+            (erc--server-reconnecting (buffer-local-variables)))
         (erc-open erc-session-server erc-session-port erc-server-current-nick
                   erc-session-user-full-name t erc-session-password
                   nil nil nil erc-session-client-certificate
@@ -824,8 +828,7 @@ When `erc-server-reconnect-attempts' is a number, increment
         (if (not reconnect-p)
             ;; terminate, do not reconnect
             (progn
-              (setq erc--server-reconnecting nil
-                    erc--server-reconnect-timer nil)
+              (setq erc--server-reconnect-timer nil)
               (erc-display-message nil 'error (current-buffer)
                                    'terminated ?e event)
               (set-buffer-modified-p nil))
diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 1052c8c4c03..352f72e6178 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -3834,10 +3834,8 @@ the message given by REASON."
       (with-suppressed-warnings ((obsolete erc-server-reconnecting)
                                  (obsolete erc-reuse-buffers))
         (if erc-reuse-buffers
-            (progn (cl-assert (not erc--server-reconnecting))
-                   (cl-assert (not erc-server-reconnecting)))
-          (setq erc--server-reconnecting nil
-                erc-server-reconnecting nil)))))
+            (cl-assert (not erc-server-reconnecting))
+          (setq erc-server-reconnecting nil)))))
   t)
 
 (defun erc-cmd-RECONNECT (&rest args)