Subject: Re: bug#51753: ERC switches to channel buffer on reconnect

From: "J.P." <[email-masked]>
Date: Fri, 19 Nov 2021 02:36:40 -0800

Lars Ingebrigtsen <[email-masked]> writes:

>> However, if people want something different to happen when
>> automatically reconnecting, we'd probably have to remember whether
>> `erc-server-reconnect-count' was ever positive before crossing the
>> logical connection threshold for the current session.
>>
>> This may come down to having `erc-connection-established' record the
>> count prior to resetting it (perhaps in a new, internal variable). And
>> then, during re-JOINs, `erc-setup-buffer' could weigh that recorded
>> value against some new option, like an `erc-display-reconnect' (or
>> whatever), and proceed accordingly.
>
> Sounds good to me.

I wasn't sure if that meant I was supposed to work on this. If not,
please disregard.

Otherwise, the tests are in #48598 [1]. As for the name of the option
itself, I basically punted by going with `erc-reconnect-buffer' to try
and stay close to `erc-join-buffer'. If that doesn't matter, perhaps
`erc-reconnect-display' would be a better fit since we already have an
`erc-query-display' (even though that one's not as closely related).
Anyone with an opinion, please advise. Thanks.

[1] Around line 4736:

    https://gitlab.com/jpneverwas/erc-tools/-/raw/master/bugs/48598/patches/wip/0013-Update-ERC-scenarios-with-session-centric-naming.patch

    Or browsable (JS):

    https://gitlab.com/jpneverwas/erc-v3/-/blob/1333bda3c0d11ff06b1b2acbb27864c90d5ba303/test/erc-scenarios.el#L1668

>From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <[email-masked]>
Date: Thu, 18 Nov 2021 23:39:54 -0800
Subject: [PATCH 01/29] Customize displaying of ERC buffers on reconnect

* lisp/erc/erc-backend.el (erc--server-last-reconnect-count):
Add variable to record last reconnect tally.

* lisp/erc/erc.el (erc-reconnect-buffer): Add option to specify
channel-buffer display behavior on reconnect.
(erc-setup-buffer): Use option `erc-reconnect-buffer' if warranted.
(erc-connection-established): Record reconnect count in internal var
before resetting.
---
 lisp/erc/erc-backend.el |  3 +++
 lisp/erc/erc.el         | 24 ++++++++++++++++++++++--
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/lisp/erc/erc-backend.el b/lisp/erc/erc-backend.el
index 69f63dfbc4..4b39bd8a30 100644
--- a/lisp/erc/erc-backend.el
+++ b/lisp/erc/erc-backend.el
@@ -193,6 +193,9 @@ erc-server-connected
 (defvar-local erc-server-reconnect-count 0
   "Number of times we have failed to reconnect to the current server.")
 
+(defvar-local erc--server-last-reconnect-count 0
+  "Snapshot of reconnect count when connection established.")
+
 (defvar-local erc-server-quitting nil
   "Non-nil if the user requests a quit.")
 
diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index c5a4fbe5a0..21ae25d920 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -1521,6 +1521,22 @@ erc-join-buffer
                  (const :tag "Use current buffer" buffer)
                  (const :tag "Use current buffer" t)))
 
+(defcustom erc-reconnect-buffer nil
+  "How (and whether) to display a channel buffer upon reconnecting.
+
+This only affects automatic reconnections and is ignored when issuing a
+/reconnect command or reinvoking `erc-tls' with the same args (assuming
+success, of course).  See `erc-join-buffer' for a description of
+possible values."
+  :group 'erc-buffers
+  :type '(choice (const :tag "Use value of `erc-join-buffer'" nil)
+                 (const :tag "Split window and select" window)
+                 (const :tag "Split window, don't select" window-noselect)
+                 (const :tag "New frame" frame)
+                 (const :tag "Bury in new buffer" bury)
+                 (const :tag "Use current buffer" buffer)
+                 (const :tag "Use current buffer" t)))
+
 (defcustom erc-frame-alist nil
   "Alist of frame parameters for creating erc frames.
 A value of nil means to use `default-frame-alist'."
@@ -1950,7 +1966,10 @@ erc-update-modules
 
 (defun erc-setup-buffer (buffer)
   "Consults `erc-join-buffer' to find out how to display `BUFFER'."
-  (pcase erc-join-buffer
+  (pcase (if (zerop (erc-with-server-buffer
+                      erc--server-last-reconnect-count))
+             erc-join-buffer
+           (or erc-reconnect-buffer erc-join-buffer))
     ('window
      (if (active-minibuffer-window)
          (display-buffer buffer)
@@ -4722,7 +4741,8 @@ erc-connection-established
             (nick (car (erc-response.command-args parsed)))
             (buffer (process-buffer proc)))
         (setq erc-server-connected t)
-	(setq erc-server-reconnect-count 0)
+        (setq erc--server-last-reconnect-count erc-server-reconnect-count
+              erc-server-reconnect-count 0)
         (erc-update-mode-line)
         (erc-set-initial-user-mode nick buffer)
         (erc-server-setup-periodical-ping buffer)
-- 
2.31.1