Add hook to regain nickname in ERC

* lisp/erc/erc-backend.el (erc-server-reconnect-timeout): Mention
`erc-nickname-in-use-functions' in doc string.
* lisp/erc/erc.el (erc-nickname-in-use-functions,
erc-regain-nick-on-connect): Add abnormal hook and possible value to
handle stale connections preventing a desired nick from being reissued
by the server.  Follows directly from bug#62044.
(erc-nickname-in-use): Call `erc-nickname-in-use-functions'.
* test/lisp/erc/erc-scenarios-base-renick.el
(erc-scenarios-base-renick-auto-regain): New test.
* test/lisp/erc/resources/base/renick/regain/normal-again.eld: New file.
* test/lisp/erc/resources/base/renick/regain/normal.eld: New file.

3 files changed, 152 insertions, 0 deletions

diff --git a/test/lisp/erc/erc-scenarios-base-renick.el b/test/lisp/erc/erc-scenarios-base-renick.el
index f1723200533..f8350676fb7 100644
--- a/test/lisp/erc/erc-scenarios-base-renick.el
+++ b/test/lisp/erc/erc-scenarios-base-renick.el
@@ -303,4 +303,47 @@
       (should-not (search-forward "now known as frenemy" nil t))
       (erc-d-t-search-for 25 "I have lost"))))
 
+;; The server rejects your nick during registration, so ERC acquires a
+;; placeholder and successfully renicks once the connection is up.
+;; See also `erc-scenarios-base-renick-self-auto'.
+
+(ert-deftest erc-scenarios-base-renick-auto-regain ()
+  :tags '(:expensive-test)
+  (erc-scenarios-common-with-cleanup
+      ((erc-server-flood-penalty 0.1)
+       (erc-scenarios-common-dialog "base/renick/regain")
+       (dumb-server (erc-d-run "localhost" t 'normal 'normal-again))
+       (port (process-contact dumb-server :service))
+       (erc-server-auto-reconnect t)
+       (erc-modules (cons 'sasl erc-modules))
+       (erc-nickname-in-use-functions '(erc-regain-nick-on-connect))
+       (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"
+                                :user "tester"
+                                :password "changeme"
+                                :full-name "tester")
+        (funcall expect 10 "Last login from")
+        (erc-cmd-JOIN "#test")))
+
+    (with-current-buffer (erc-d-t-wait-for 10 (get-buffer "#test"))
+      (funcall expect 10 "was created on"))
+
+    (ert-info ("Service restored")
+      (with-current-buffer "Libera.Chat"
+        (erc-d-t-wait-for 10 erc--server-reconnect-timer)
+        (funcall expect 10 "Connection failed!")
+        (funcall expect 10 "already in use")
+        (funcall expect 10 "changed mode for tester`")
+        (funcall expect 10 "Last login from")
+        (funcall expect 10 "Your new nickname is tester")))
+
+    (with-current-buffer (get-buffer "#test")
+      (funcall expect 10 "tester ")
+      (funcall expect 10 "was created on"))))
+
+
 ;;; erc-scenarios-base-renick.el ends here
diff --git a/test/lisp/erc/resources/base/renick/regain/normal-again.eld b/test/lisp/erc/resources/base/renick/regain/normal-again.eld
new file mode 100644
index 00000000000..c0529052c70
--- /dev/null
+++ b/test/lisp/erc/resources/base/renick/regain/normal-again.eld
@@ -0,0 +1,56 @@
+;; -*- mode: lisp-data; -*-
+((cap 10 "CAP REQ :sasl"))
+((nick 10 "NICK tester"))
+((user 10 "USER tester 0 * :tester"))
+
+((authenticate 10 "AUTHENTICATE PLAIN")
+ (0.04 ":tantalum.libera.chat NOTICE * :*** Checking Ident")
+ (0.01 ":tantalum.libera.chat NOTICE * :*** Looking up your hostname...")
+ (0.01 ":tantalum.libera.chat NOTICE * :*** Couldn't look up your hostname")
+ (0.06 ":tantalum.libera.chat NOTICE * :*** No Ident response")
+ (0.02 ":tantalum.libera.chat CAP * ACK :sasl")
+ (0.03 ":tantalum.libera.chat 433 * tester :Nickname is already in use."))
+
+((nick 10 "NICK tester`")
+ (0.03 "AUTHENTICATE +"))
+
+((authenticate 10 "AUTHENTICATE AHRlc3RlcgBjaGFuZ2VtZQ==")
+ (0.06 ":tantalum.libera.chat 900 tester` tester`!tester@127.0.0.1 tester :You are now logged in as tester")
+ (0.02 ":tantalum.libera.chat 903 tester` :SASL authentication successful"))
+
+((cap 10 "CAP END")
+ (0.02 ":tantalum.libera.chat 001 tester` :Welcome to the Libera.Chat Internet Relay Chat Network tester`")
+ (0.02 ":tantalum.libera.chat 002 tester` :Your host is tantalum.libera.chat[93.158.237.2/6697], running version solanum-1.0-dev")
+ (0.02 ":tantalum.libera.chat 003 tester` :This server was created Mon Feb 13 2023 at 12:05:04 UTC")
+ (0.01 ":tantalum.libera.chat 004 tester` tantalum.libera.chat solanum-1.0-dev DGMQRSZaghilopsuwz CFILMPQRSTbcefgijklmnopqrstuvz bkloveqjfI")
+ (0.01 ":tantalum.libera.chat 005 tester` WHOX MONITOR=100 SAFELIST ELIST=CMNTU ETRACE FNC CALLERID=g KNOCK CHANTYPES=# EXCEPTS INVEX CHANMODES=eIbq,k,flj,CFLMPQRSTcgimnprstuz :are supported by this server")
+ (0.01 ":tantalum.libera.chat 005 tester` CHANLIMIT=#:250 PREFIX=(ov)@+ MAXLIST=bqeI:100 MODES=4 NETWORK=Libera.Chat STATUSMSG=@+ CASEMAPPING=rfc1459 NICKLEN=16 MAXNICKLEN=16 CHANNELLEN=50 TOPICLEN=390 DEAF=D :are supported by this server")
+ (0.03 ":tantalum.libera.chat 005 tester` TARGMAX=NAMES:1,LIST:1,KICK:1,WHOIS:1,PRIVMSG:4,NOTICE:4,ACCEPT:,MONITOR: EXTBAN=$,ajrxz :are supported by this server")
+ (0.01 ":tantalum.libera.chat 251 tester` :There are 70 users and 42977 invisible on 28 servers")
+ (0.00 ":tantalum.libera.chat 252 tester` 38 :IRC Operators online")
+ (0.00 ":tantalum.libera.chat 253 tester` 87 :unknown connection(s)")
+ (0.00 ":tantalum.libera.chat 254 tester` 22908 :channels formed")
+ (0.00 ":tantalum.libera.chat 255 tester` :I have 2507 clients and 1 servers")
+ (0.00 ":tantalum.libera.chat 265 tester` 2507 3232 :Current local users 2507, max 3232")
+ (0.00 ":tantalum.libera.chat 266 tester` 43047 51777 :Current global users 43047, max 51777")
+ (0.00 ":tantalum.libera.chat 250 tester` :Highest connection count: 3233 (3232 clients) (284887 connections received)")
+ (0.03 ":tantalum.libera.chat 375 tester` :- tantalum.libera.chat Message of the Day - ")
+ (0.00 ":tantalum.libera.chat 372 tester` :- This server provided by Hyperfilter (https://hyperfilter.com)")
+ (0.00 ":tantalum.libera.chat 372 tester` :- Email:                      support@libera.chat")
+ (0.02 ":tantalum.libera.chat 376 tester` :End of /MOTD command."))
+
+((mode 10 "MODE tester` +i")
+ (0.01 ":tester` MODE tester` :+Ziw")
+ (0.02 ":SaslServ!SaslServ@services.libera.chat NOTICE tester` :Last login from: \2~tester@127.0.0.1\2 on Apr 07 01:36:25 2023 +0000."))
+
+((nick 10 "NICK tester")
+ (0.02 ":tester`!~tester@127.0.0.1 NICK :tester"))
+
+((join 10 "JOIN #test")
+ (0.02 ":tester!~tester@127.0.0.1 JOIN #test")
+ (0.02 ":tantalum.libera.chat 353 tester = #test :tester zbyqbepbqre7 pusevgfpu Thrfg2187 zngbeb qnexNssvavgl wrebzr- rqpentt Ilehf grfg2 AvtugZbaxrl pevfgvvbna xrivap_ fnvybePng shohxv gxan arrqyr avpx16 NeanhqW_kzcc jvyyr wrnaogeq Wnarg cnefavc0 Xbentt RcvpArb flfqrs wfgbxre hafcrag__ Lbevpx_")
+ (0.02 ":tantalum.libera.chat 366 tester #test :End of /NAMES list."))
+
+((mode 10 "MODE #test")
+ (0.02 ":tantalum.libera.chat 324 tester #test +nt")
+ (0.02 ":tantalum.libera.chat 329 tester #test 1621432263"))
diff --git a/test/lisp/erc/resources/base/renick/regain/normal.eld b/test/lisp/erc/resources/base/renick/regain/normal.eld
new file mode 100644
index 00000000000..9f4df70e580
--- /dev/null
+++ b/test/lisp/erc/resources/base/renick/regain/normal.eld
@@ -0,0 +1,53 @@
+;; -*- mode: lisp-data; -*-
+((cap 10 "CAP REQ :sasl"))
+((nick 10 "NICK tester"))
+((user 10 "USER tester 0 * :tester"))
+
+((authenticate 10 "AUTHENTICATE PLAIN")
+ (0.02 ":cadmium.libera.chat NOTICE * :*** Checking Ident")
+ (0.01 ":cadmium.libera.chat NOTICE * :*** Looking up your hostname...")
+ (0.01 ":cadmium.libera.chat NOTICE * :*** Couldn't look up your hostname")
+ (0.06 ":cadmium.libera.chat NOTICE * :*** No Ident response")
+ (0.09 ":cadmium.libera.chat CAP * ACK :sasl")
+ (0.01 "AUTHENTICATE +"))
+
+((authenticate 10 "AUTHENTICATE AHRlc3RlcgBjaGFuZ2VtZQ==")
+ (0.03 ":cadmium.libera.chat 900 tester tester!tester@127.0.0.1 tester :You are now logged in as tester")
+ (0.01 ":cadmium.libera.chat 903 tester :SASL authentication successful"))
+
+((cap 10 "CAP END")
+ (0.03 ":cadmium.libera.chat 001 tester :Welcome to the Libera.Chat Internet Relay Chat Network tester")
+ (0.02 ":cadmium.libera.chat 002 tester :Your host is cadmium.libera.chat[103.196.37.95/6697], running version solanum-1.0-dev")
+ (0.01 ":cadmium.libera.chat 003 tester :This server was created Wed Jan 25 2023 at 10:22:45 UTC")
+ (0.01 ":cadmium.libera.chat 004 tester cadmium.libera.chat solanum-1.0-dev DGMQRSZaghilopsuwz CFILMPQRSTbcefgijklmnopqrstuvz bkloveqjfI")
+ (0.00 ":cadmium.libera.chat 005 tester CALLERID=g WHOX ETRACE FNC SAFELIST ELIST=CMNTU KNOCK MONITOR=100 CHANTYPES=# EXCEPTS INVEX CHANMODES=eIbq,k,flj,CFLMPQRSTcgimnprstuz :are supported by this server")
+ (0.01 ":cadmium.libera.chat 005 tester CHANLIMIT=#:250 PREFIX=(ov)@+ MAXLIST=bqeI:100 MODES=4 NETWORK=Libera.Chat STATUSMSG=@+ CASEMAPPING=rfc1459 NICKLEN=16 MAXNICKLEN=16 CHANNELLEN=50 TOPICLEN=390 DEAF=D :are supported by this server")
+ (0.01 ":cadmium.libera.chat 005 tester TARGMAX=NAMES:1,LIST:1,KICK:1,WHOIS:1,PRIVMSG:4,NOTICE:4,ACCEPT:,MONITOR: EXTBAN=$,ajrxz :are supported by this server")
+ (0.01 ":cadmium.libera.chat 251 tester :There are 70 users and 42996 invisible on 28 servers")
+ (0.02 ":cadmium.libera.chat 252 tester 38 :IRC Operators online")
+ (0.01 ":cadmium.libera.chat 253 tester 57 :unknown connection(s)")
+ (0.01 ":cadmium.libera.chat 254 tester 22912 :channels formed")
+ (0.01 ":cadmium.libera.chat 255 tester :I have 2499 clients and 1 servers")
+ (0.01 ":cadmium.libera.chat 265 tester 2499 4187 :Current local users 2499, max 4187")
+ (0.01 ":cadmium.libera.chat 266 tester 43066 51827 :Current global users 43066, max 51827")
+ (0.01 ":cadmium.libera.chat 250 tester :Highest connection count: 4188 (4187 clients) (319420 connections received)")
+ (0.01 ":cadmium.libera.chat 375 tester :- cadmium.libera.chat Message of the Day - ")
+ (0.01 ":cadmium.libera.chat 372 tester :- This server kindly provided by Mach Dilemma (www.m-d.net)")
+ (0.01 ":cadmium.libera.chat 372 tester :- Welcome to Libera Chat, the IRC network for")
+ (0.00 ":cadmium.libera.chat 372 tester :- Email:                      support@libera.chat")
+ (0.00 ":cadmium.libera.chat 376 tester :End of /MOTD command.")
+ (0.00 ":tester MODE tester :+Ziw")
+ (0.02 ":SaslServ!SaslServ@services.libera.chat NOTICE tester :Last login from: \2~tester@127.0.0.1\2 on Apr 07 01:02:11 2023 +0000."))
+
+((mode 10 "MODE tester +i"))
+
+((join 10 "JOIN #test")
+ (0.09 ":tester!~tester@127.0.0.1 JOIN #test"))
+
+((mode 10 "MODE #test")
+ (0.03 ":cadmium.libera.chat 353 tester = #test :tester zbyqbepbqre7 pusevgfpu Thrfg2187 zngbeb qnexNssvavgl wrebzr- rqpentt Ilehf grfg2 AvtugZbaxrl pevfgvvbna xrivap_ fnvybePng shohxv gxan arrqyr avpx16 NeanhqW_kzcc Lbevpx_ hafcrag__ wfgbxre flfqrs RcvpArb Xbentt jvyyr cnefavc0 Wnarg wrnaogeq")
+ (0.02 ":cadmium.libera.chat 366 tester #test :End of /NAMES list.")
+ (0.00 ":cadmium.libera.chat 324 tester #test +nt")
+ (0.01 ":cadmium.libera.chat 329 tester #test 1621432263"))
+
+((drop 0 DROP))