bug#43582: 27.1; Avoid topic changes to topicless group

[dick]

Note gnus.general appears *twice* because `gnus-topic-change-level' on a
topicless group will blithely add it to gnus-topic-alist without updating the
group buffer to reflect its new position in the "topology."

emacs-27.1 -Q --batch \
--eval "(custom-set-variables \
 '(network-security-level (quote low)) \
 '(gnus-interactive-exit (quote quiet)) \
 '(gnus-large-newsgroup 4000) \
 '(gnus-select-method (quote (nntp \"news.gmane.io\"))) \
 '(gnus-add-timestamp-to-message (quote log)) \
 '(gnus-before-startup-hook (quote (toggle-debug-on-error))) \
 '(gnus-always-read-dribble-file t) \
 '(gnus-use-dribble-file nil) \
 '(gnus-read-newsrc-file nil) \
 '(gnus-parameters (quote ((\"^nntp\" (display . 1000))))) \
 '(gnus-summary-prepared-hook (quote (gnus-summary-hide-all-threads))) \
 '(gnus-startup-file \"/var/tmp/foo\") \
 )" \
-l gnus-topic \
--eval "(add-hook 'gnus-group-mode-hook 'gnus-topic-mode)" \
-f gnus \
--eval "(gnus-server-open-all-servers)" \
--eval "(gnus-fetch-group \"nntp+news.gmane.io:gmane.emacs.gnus.general\")" \
--eval "(with-current-buffer (gnus-summary-buffer-name 
\"nntp+news.gmane.io:gmane.emacs.gnus.general\") (gnus-summary-exit))" \
--eval "(goto-char (point-min))" \
--eval "(save-excursion (gnus-group-subscribe nil))" \
--eval "(gnus-topic-move-group nil \"misc\")" \
--eval "(princ (buffer-string) #'external-debugging-output)"

>From 88fe5b506efc230cbf172389844502dcc33d98c6 Mon Sep 17 00:00:00 2001
From: dickmao <none>
Date: Wed, 23 Sep 2020 17:15:09 -0400
Subject: [PATCH] Bad things happen when applying topic changes to topicless
 groups

* lisp/gnus/gnus-topic.el (gnus-topic-change-level):
Do not change gnus-topic-alist when group is outside "toplogy."
---
 lisp/gnus/gnus-topic.el | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/lisp/gnus/gnus-topic.el b/lisp/gnus/gnus-topic.el
index ffd26bb30f..c913002f70 100644
--- a/lisp/gnus/gnus-topic.el
+++ b/lisp/gnus/gnus-topic.el
@@ -897,9 +897,7 @@ gnus-topic-change-level
     (let ((inhibit-read-only t))
       (unless gnus-topic-inhibit-change-level
        (gnus-group-goto-group (or (car (nth 1 previous)) group))
-       (when (and gnus-topic-mode
-                  gnus-topic-alist
-                  (not gnus-topic-inhibit-change-level))
+       (when (and gnus-topic-mode gnus-topic-alist (gnus-current-topic))
          ;; Remove the group from the topics.
          (if (and (< oldlevel gnus-level-zombie)
                   (>= level gnus-level-zombie))
-- 
2.26.2



In GNU Emacs 27.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
 of 2020-08-25 built on dick
Repository revision: ddd82c2b1261b2c5d5425c0738112f47e2bb18bf
Repository branch: gnus-dev-27
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
System Description: Ubuntu 18.04.4 LTS

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