bug#50010: 28.0.50; ERC is too presumptuous with announced server names

["J.P." <jp@neverwas.me>]

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Tags: patch

Hi, this may seem innocuous, but it's relevant to the more offensive
"omnibugs" I'm currently peddling [1]. Please see the commit log for
details. As usual, I'm happy to answer any questions and/or provide
specific examples. Thanks.


[1] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=48598
    https://debbugs.gnu.org/cgi/bugreport.cgi?bug=49860


In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.30, cairo version 1.17.4)
 of 2021-08-09 built on localhost
Repository revision: aeec97fae0ccfcc4dc406a5e0e4c0a94b834cac4
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Fedora 34 (Workstation Edition)

Configured features:
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From f66f7b51ed099f911aefb26294c7b1524e973e37 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <jp@neverwas.me>
Date: Mon, 14 Jun 2021 23:40:45 -0700
Subject: [PATCH] Don't set erc-server-announced-name unless known

* lisp/erc/erc.el (erc-open): this function is called by the
entry-point functions/commands `erc' and `erc-tls', as well as by
query commands and join hooks to prepare a new/reused target buffer
for an existing server process. In the case of the former, the
variable erc-server-announced-name may be set in the current buffer
when an entry point command is invoked. If that buffer is another
server buffer in which the variable is already set, it's copied to the
new server buffer when the dialed servers match.  But there's no
guarantee that the announced name will match when actually announced
during an introductory burst. This also causes confusion in protocol
logs and may make it more difficult to reproduce bugs. Setting it to
nil helps ensure a consistent environment when setting up a buffer for
all newly dialed server connections.
---
 lisp/erc/erc.el | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 73202016ba..fe57bc1998 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -1991,11 +1991,7 @@ erc-open
 private key and the certificate.
 
 Returns the buffer for the given server or channel."
-  (let ((server-announced-name (when (and (boundp 'erc-session-server)
-                                          (string= server erc-session-server))
-                                 erc-server-announced-name))
-        (connected-p (unless connect erc-server-connected))
-        (buffer (erc-get-buffer-create server port channel))
+  (let ((buffer (erc-get-buffer-create server port channel))
         (old-buffer (current-buffer))
         old-point
         continued-session)
@@ -2006,8 +2002,11 @@ erc-open
     (let ((old-recon-count erc-server-reconnect-count))
       (erc-mode)
       (setq erc-server-reconnect-count old-recon-count))
-    (setq erc-server-announced-name server-announced-name)
-    (setq erc-server-connected connected-p)
+    (unless connect
+      (setq erc-server-announced-name (with-current-buffer old-buffer
+                                        erc-server-announced-name))
+      (setq erc-server-connected (with-current-buffer old-buffer
+                                   erc-server-connected)))
     ;; connection parameters
     (setq erc-server-process process)
     (setq erc-insert-marker (make-marker))
-- 
2.31.1