Add probing erc-server-reconnect-function variant

* lisp/erc/erc-backend.el (erc-server-reconnect-timeout): Replace
questionable claim with recommendation for alternate value when
experiencing nick rejections.
(erc-server-reconnect-function): Add new, somewhat experimental value
`erc-server-delayed-check-reconnect'.
(erc--server-connect-function): Add variable for process-dialing
monitor, a function.
(erc--server-propagate-failed-connection): Add function to serve as
default monitor to run on process creation and maybe execute failure
handlers.
(erc-server-connect): Run `erc--server-connect-function' for async
processes one second after creation.
(erc--server-reconnect-timeout, erc--server-reconnect-timeout-check,
erc--server-reconnect-timeout-scale-function,
erc--server-reconnect-timeout-double): Add supporting variables and
functions for `erc-server-delayed-check-reconnect'.
(erc-server-delayed-check-reconnect): Add possible alternate value for
option `erc-server-reconnect-function' that only attempts to reconnect
after hearing back from the server.
(erc-schedule-reconnect): Ensure previous `erc-server-process' is
deleted.
* test/lisp/erc/erc-scenarios-base-auto-recon.el: New file.
* test/lisp/erc/resources/base/reconnect/just-eof.eld: New file.
* test/lisp/erc/resources/base/reconnect/just-ping.eld: New file.
* test/lisp/erc/resources/base/reconnect/ping-pong.eld: New file.
* test/lisp/erc/resources/base/reconnect/unexpected-disconnect.eld:
New file.
* test/lisp/erc/resources/erc-scenarios-common.el
(erc-scenarios-common--make-bindings): Shadow
`timer-list'.  (Bug#62044.)

6 files changed, 179 insertions, 0 deletions

diff --git a/test/lisp/erc/erc-scenarios-base-auto-recon.el b/test/lisp/erc/erc-scenarios-base-auto-recon.el
new file mode 100644
index 00000000000..40e2c23408b
--- /dev/null
+++ b/test/lisp/erc/erc-scenarios-base-auto-recon.el
@@ -0,0 +1,141 @@
+;;; erc-scenarios-base-auto-recon.el --- auto-recon scenarios -*- lexical-binding: t -*-
+
+;; Copyright (C) 2023 Free Software Foundation, Inc.
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Code:
+
+(require 'ert-x)
+(eval-and-compile
+  (let ((load-path (cons (ert-resource-directory) load-path)))
+    (require 'erc-scenarios-common)))
+
+(defun erc-scenarios-base-auto-recon--get-unused-port ()
+  (let ((server (make-network-process :name "*erc-scenarios-base-auto-recon*"
+                                      :host "localhost"
+                                      :service t
+                                      :server t)))
+    (delete-process server)
+    (process-contact server :service)))
+
+;; This demos one possible flavor of intermittent service.
+;; It may end up needing to be marked :unstable.
+
+(ert-deftest erc-scenarios-base-auto-recon-unavailable ()
+  :tags '(:expensive-test)
+  (erc-scenarios-common-with-cleanup
+      ((erc-server-flood-penalty 0.1)
+       (port (erc-scenarios-base-auto-recon--get-unused-port))
+       (erc--server-reconnect-timeout-scale-function (lambda (_) 1))
+       (erc-server-auto-reconnect t)
+       (erc-server-reconnect-function #'erc-server-delayed-check-reconnect)
+       (expect (erc-d-t-make-expecter))
+       (erc-scenarios-common-dialog "base/reconnect")
+       (dumb-server nil))
+
+    (ert-info ("Dialing fails: nobody home")
+      (with-current-buffer (erc :server "127.0.0.1"
+                                :port port
+                                :nick "tester"
+                                :full-name "tester")
+        (erc-d-t-wait-for 10 (not (erc-server-process-alive)))
+        (erc-d-t-wait-for 10 erc--server-reconnect-timer)
+        (funcall expect 10 "Opening connection")
+        (funcall expect 10 "failed")
+
+        (ert-info ("Reconnect function freezes attempts at 1")
+          (funcall expect 10 '(: "reconnecting" (+ nonl) "attempt 1/2"))
+          (funcall expect 10 "nobody home")
+          (funcall expect 10 '(: "reconnecting" (+ nonl) "attempt 1/2"))
+          (funcall expect 10 "nobody home"))))
+
+    (ert-info ("Service appears")
+      (setq dumb-server (erc-d-run "localhost" port
+                                   'just-eof 'unexpected-disconnect))
+      (with-current-buffer (format "127.0.0.1:%d" port)
+        (funcall expect 10 "server is in debug mode")
+        (should (equal (buffer-name) "FooNet"))))
+
+    (ert-info ("Service interrupted, reconnect starts again")
+      (with-current-buffer "FooNet"
+        (funcall expect 10 "failed")
+        (funcall expect 10 '(: "reconnecting" (+ nonl) "attempt 1/2"))))
+
+    (ert-info ("Service restored")
+      (delete-process dumb-server)
+      (setq dumb-server (erc-d-run "localhost" port
+                                   'just-eof 'unexpected-disconnect))
+      (with-current-buffer "FooNet"
+        (funcall expect 10 "server is in debug mode")))
+
+    (ert-info ("Service interrupted a third time, reconnect starts yet again")
+      (with-current-buffer "FooNet"
+        (funcall expect 10 "failed")
+        (funcall expect 10 '(: "reconnecting" (+ nonl) "attempt 1/2"))
+        (erc-cmd-RECONNECT "cancel")
+        (funcall expect 10 "canceled")))))
+
+;; In this test, a listener accepts but doesn't respond to any messages.
+
+(ert-deftest erc-scenarios-base-auto-recon-no-proto ()
+  :tags '(:expensive-test)
+  (erc-scenarios-common-with-cleanup
+      ((erc-server-flood-penalty 0.1)
+       (erc-scenarios-common-dialog "base/reconnect")
+       (erc-d-auto-pong nil)
+       (dumb-server (erc-d-run "localhost" t 'unexpected-disconnect))
+       (port (process-contact dumb-server :service))
+       (erc--server-reconnect-timeout-scale-function (lambda (_) 1))
+       (erc--server-reconnect-timeout-check 0.5)
+       (erc-server-auto-reconnect t)
+       (erc-server-reconnect-function #'erc-server-delayed-check-reconnect)
+       (expect (erc-d-t-make-expecter)))
+
+    (ert-info ("Session succeeds but cut short")
+      (with-current-buffer (erc :server "127.0.0.1"
+                                :port port
+                                :nick "tester"
+                                :full-name "tester")
+        (funcall expect 10 "server is in debug mode")
+        (should (equal (buffer-name) "FooNet"))
+        (erc-d-t-wait-for 10 erc--server-reconnect-timer)
+        (delete-process dumb-server)
+        (funcall expect 10 "failed")
+
+        (ert-info ("Reconnect function freezes attempts at 1")
+          (funcall expect 10 '(: "reconnecting" (+ nonl) "attempt 1/2"))
+          (funcall expect 10 "nobody home")
+          (funcall expect 10 "timed out while dialing")
+          (funcall expect 10 '(: "reconnecting" (+ nonl) "attempt 1/2"))
+          (funcall expect 10 "nobody home"))))
+
+    (ert-info ("Service restored")
+      (setq dumb-server (erc-d-run "localhost" port
+                                   'just-ping
+                                   'ping-pong
+                                   'unexpected-disconnect))
+      (with-current-buffer "FooNet"
+        (funcall expect 30 "server is in debug mode")))
+
+    (ert-info ("Service interrupted again, reconnect starts again")
+      (with-current-buffer "FooNet"
+        (funcall expect 10 "failed")
+        (funcall expect 10 '(: "reconnecting" (+ nonl) "attempt 1/2"))
+        (erc-cmd-RECONNECT "cancel")
+        (funcall expect 10 "canceled")))))
+
+;;; erc-scenarios-base-auto-recon.el ends here
diff --git a/test/lisp/erc/resources/base/reconnect/just-eof.eld b/test/lisp/erc/resources/base/reconnect/just-eof.eld
new file mode 100644
index 00000000000..c80a39b3170
--- /dev/null
+++ b/test/lisp/erc/resources/base/reconnect/just-eof.eld
@@ -0,0 +1,3 @@
+;; -*- mode: lisp-data; -*-
+((eof 5 EOF))
+((drop 0 DROP))
diff --git a/test/lisp/erc/resources/base/reconnect/just-ping.eld b/test/lisp/erc/resources/base/reconnect/just-ping.eld
new file mode 100644
index 00000000000..d57888b42d3
--- /dev/null
+++ b/test/lisp/erc/resources/base/reconnect/just-ping.eld
@@ -0,0 +1,4 @@
+;; -*- mode: lisp-data; -*-
+((ping 20 "PING"))
+
+((eof 10 EOF))
diff --git a/test/lisp/erc/resources/base/reconnect/ping-pong.eld b/test/lisp/erc/resources/base/reconnect/ping-pong.eld
new file mode 100644
index 00000000000..b3d36cf6cec
--- /dev/null
+++ b/test/lisp/erc/resources/base/reconnect/ping-pong.eld
@@ -0,0 +1,6 @@
+;; -*- mode: lisp-data; -*-
+((ping 10 "PING ")
+ (0 "PONG fake"))
+
+((eof 10 EOF))
+((drop 0 DROP))
diff --git a/test/lisp/erc/resources/base/reconnect/unexpected-disconnect.eld b/test/lisp/erc/resources/base/reconnect/unexpected-disconnect.eld
new file mode 100644
index 00000000000..386d0f4b085
--- /dev/null
+++ b/test/lisp/erc/resources/base/reconnect/unexpected-disconnect.eld
@@ -0,0 +1,24 @@
+;; -*- mode: lisp-data; -*-
+((nick 10 "NICK tester"))
+((user 10 "USER user 0 * :tester")
+ (0 ":irc.foonet.org 001 tester :Welcome to the foonet IRC Network tester")
+ (0 ":irc.foonet.org 002 tester :Your host is irc.foonet.org, running version oragono-2.6.0-7481bf0385b95b16")
+ (0 ":irc.foonet.org 003 tester :This server was created Tue, 04 May 2021 05:06:18 UTC")
+ (0 ":irc.foonet.org 004 tester irc.foonet.org oragono-2.6.0-7481bf0385b95b16 BERTZios CEIMRUabefhiklmnoqstuv Iabefhkloqv")
+ (0 ":irc.foonet.org 005 tester AWAYLEN=390 BOT=B CASEMAPPING=ascii CHANLIMIT=#:100 CHANMODES=Ibe,k,fl,CEMRUimnstu CHANNELLEN=64 CHANTYPES=# ELIST=U EXCEPTS EXTBAN=,m FORWARD=f INVEX KICKLEN=390 :are supported by this server")
+ (0 ":irc.foonet.org 005 tester MAXLIST=beI:60 MAXTARGETS=4 MODES MONITOR=100 NETWORK=FooNet NICKLEN=32 PREFIX=(qaohv)~&@%+ STATUSMSG=~&@%+ TARGMAX=NAMES:1,LIST:1,KICK:1,WHOIS:1,USERHOST:10,PRIVMSG:4,TAGMSG:4,NOTICE:4,MONITOR:100 TOPICLEN=390 UTF8MAPPING=rfc8265 UTF8ONLY WHOX :are supported by this server")
+ (0 ":irc.foonet.org 005 tester draft/CHATHISTORY=100 :are supported by this server")
+ (0 ":irc.foonet.org 251 tester :There are 0 users and 3 invisible on 1 server(s)")
+ (0 ":irc.foonet.org 252 tester 0 :IRC Operators online")
+ (0 ":irc.foonet.org 253 tester 0 :unregistered connections")
+ (0 ":irc.foonet.org 254 tester 1 :channels formed")
+ (0 ":irc.foonet.org 255 tester :I have 3 clients and 0 servers")
+ (0 ":irc.foonet.org 265 tester 3 3 :Current local users 3, max 3")
+ (0 ":irc.foonet.org 266 tester 3 3 :Current global users 3, max 3")
+ (0 ":irc.foonet.org 422 tester :MOTD File is missing"))
+
+((mode-user 10 "MODE tester +i")
+ (0 ":irc.foonet.org 221 tester +i")
+ (0 ":irc.foonet.org NOTICE tester :This server is in debug mode and is logging all user I/O. If you do not wish for everything you send to be readable by the server owner(s), please disconnect."))
+
+((drop 0 DROP))
diff --git a/test/lisp/erc/resources/erc-scenarios-common.el b/test/lisp/erc/resources/erc-scenarios-common.el
index 0d9a79ae9ce..f259c88594b 100644
--- a/test/lisp/erc/resources/erc-scenarios-common.el
+++ b/test/lisp/erc/resources/erc-scenarios-common.el
@@ -121,6 +121,7 @@
       (erc-modules (copy-sequence erc-modules))
       (inhibit-interaction t)
       (auth-source-do-cache nil)
+      (timer-list (copy-sequence timer-list))
       (erc-auth-source-parameters-join-function nil)
       (erc-autojoin-channels-alist nil)
       (erc-server-auto-reconnect nil)