Respect a nil erc-session-password when reconnecting

* lisp/erc/erc.el (erc-open): Simplify `old-vars' expression.
(erc--compute-server-password): Only compute a server password when
first connecting.  For compatibility, this respects third-party code
that expects session passwords in target buffers when initially
non-nil.
* test/lisp/erc/erc-scenarios-services-misc.el
(erc-scenarios-services-auth-source-reconnect): Add new test.
* test/lisp/erc/resources/services/auth-source/recon.eld: Add new test
data file.  (Bug#59858.)

lisp/erc/erc.el

@@ -1970,7 +1970,7 @@ Returns the buffer for the given server or channel."
   (let* ((target (and channel (erc--target-from-string channel)))
          (buffer (erc-get-buffer-create server port nil target id))
          (old-buffer (current-buffer))
-         (old-vars (and (not connect) (buffer-local-variables)))
+         (old-vars (and target (buffer-local-variables)))
          (old-recon-count erc-server-reconnect-count)
          (old-point nil)
          (delayed-modules nil)
@@ -6451,6 +6451,8 @@ non-nil value is found.
 When `erc-auth-source-server-function' is non-nil, call it with NICK for
 the user field and use whatever it returns as the server password."
   (or password (and erc-auth-source-server-function
+                    (not erc--server-reconnecting)
+                    (not erc--target)
                     (funcall erc-auth-source-server-function :user nick))))
 
 (defun erc-compute-full-name (&optional full-name)

test/lisp/erc/erc-scenarios-services-misc.el

@@ -84,4 +84,63 @@
 
     (should-not (memq 'services erc-modules))))
 
+;; A user with `services' enabled connects, quits, and reconnects.  An
+;; entry in their netrc matches the network ID, which isn't known when
+;; `erc-auth-source-server-function' runs -- initially *or* on
+;; reconnect.  It's only seen by `erc-auth-source-services-function'.
+
+(ert-deftest erc-scenarios-services-auth-source-reconnect ()
+  :tags '(:expensive-test)
+  (erc-scenarios-common-with-cleanup
+      ((erc-scenarios-common-dialog "services/auth-source")
+       (erc-server-flood-penalty 0.1)
+       (dumb-server (erc-d-run "localhost" t 'recon 'recon))
+       (port (process-contact dumb-server :service))
+       (netrc-file (make-temp-file
+                    "auth-source-test" nil nil
+                    "machine FooNet login tester password changeme\n"))
+       (auth-sources (list netrc-file))
+       (auth-source-do-cache nil)
+       (erc-modules (cons 'services erc-modules))
+       (erc-use-auth-source-for-nickserv-password t) ; do consult
+       (erc-prompt-for-nickserv-password nil) ; don't prompt
+       (erc-nickserv-alist
+        (cons '(FooNet
+                "NickServ!NickServ@services.int"
+                "This nickname is registered. Please choose"
+                "NickServ" "IDENTIFY" nil nil "You are now identified for ")
+              erc-nickserv-alist))
+       (expect (erc-d-t-make-expecter))
+       (erc-scenarios-common-extra-teardown (lambda ()
+                                              (delete-file netrc-file))))
+
+    (ert-info ("Server password omitted from initial connection")
+      (with-current-buffer (erc :server "127.0.0.1"
+                                :port port
+                                :nick "tester"
+                                :user "tester"
+                                :full-name "tester")
+        (should (string= (buffer-name) (format "127.0.0.1:%d" port)))
+        (ert-info ("Services module authenticates")
+          (funcall expect 10 "This nickname is registered.")
+          (funcall expect 3 "You are now identified"))
+        (erc-cmd-JOIN "#chan")
+        (with-current-buffer (erc-d-t-wait-for 10 (get-buffer "#chan"))
+          (funcall expect 10 "the gallants desire it"))
+        (erc-cmd-QUIT "")
+        (funcall expect 3 "finished")))
+
+    (ert-info ("Server password withheld on reconnect")
+      (with-current-buffer "#chan"
+        (erc-cmd-RECONNECT))
+      (with-current-buffer "FooNet"
+        (funcall expect 10 "This nickname is registered.")
+        (funcall expect 3 "You are now identified")
+        (with-current-buffer "#chan" ; autojoined
+          (funcall expect 10 "the gallants desire it"))
+        (erc-cmd-QUIT "")
+        (funcall expect 3 "finished")))
+
+    (erc-services-mode -1)))
+
 ;;; erc-scenarios-services-misc.el ends here

test/lisp/erc/resources/services/auth-source/recon.eld

@@ -0,0 +1,48 @@
+;; -*- mode: lisp-data; -*-
+((nick 10 "NICK tester"))
+((user 5 "USER tester 0 * :tester")
+ (0.00 ":irc.foonet.net NOTICE * :*** Looking up your hostname...")
+ (0.04 ":irc.foonet.net NOTICE tester :*** Could not resolve your hostname: Domain not found; using your IP address (10.0.2.100) instead.")
+ (0.06 ":irc.foonet.net 001 tester :Welcome to the FooNet IRC Network tester!tester@10.0.2.100")
+ (0.01 ":irc.foonet.net 002 tester :Your host is irc.foonet.net, running version InspIRCd-3")
+ (0.01 ":irc.foonet.net 003 tester :This server was created 08:32:24 Dec 05 2022")
+ (0.01 ":irc.foonet.net 004 tester irc.foonet.net InspIRCd-3 BIRcgikorsw ACHIKMORTXabcefghijklmnopqrstvz :HIXabefghjkloqv")
+ (0.01 ":irc.foonet.net 005 tester ACCEPT=30 AWAYLEN=200 BOT=B CALLERID=g CASEMAPPING=ascii CHANLIMIT=#:20 CHANMODES=IXbeg,k,Hfjl,ACKMORTcimnprstz CHANNELLEN=64 CHANTYPES=# ELIST=CMNTU ESILENCE=CcdiNnPpTtx EXCEPTS=e :are supported by this server")
+ (0.01 ":irc.foonet.net 005 tester EXTBAN=,ACORTUacjrwz HOSTLEN=64 INVEX=I KEYLEN=32 KICKLEN=255 LINELEN=512 MAXLIST=I:100,X:100,b:100,e:100,g:100 MAXTARGETS=20 MODES=20 MONITOR=30 NAMELEN=128 NAMESX NETWORK=FooNet :are supported by this server")
+ (0.01 ":irc.foonet.net 005 tester NICKLEN=30 PREFIX=(qaohv)~&@%+ SAFELIST SILENCE=32 STATUSMSG=~&@%+ TOPICLEN=307 UHNAMES USERIP USERLEN=10 USERMODES=,,s,BIRcgikorw WHOX :are supported by this server")
+ (0.01 ":irc.foonet.net 251 tester :There are 2 users and 0 invisible on 2 servers")
+ (0.00 ":irc.foonet.net 253 tester 1 :unknown connections")
+ (0.00 ":irc.foonet.net 254 tester 1 :channels formed")
+ (0.00 ":irc.foonet.net 255 tester :I have 2 clients and 1 servers")
+ (0.00 ":irc.foonet.net 265 tester :Current local users: 2  Max: 3")
+ (0.00 ":irc.foonet.net 266 tester :Current global users: 2  Max: 3")
+ (0.00 ":irc.foonet.net 375 tester :irc.foonet.net message of the day")
+ (0.00 ":irc.foonet.net 372 tester :Have fun!")
+ (0.00 ":irc.foonet.net 376 tester :End of message of the day."))
+
+((mode-a 10 "MODE tester +i")
+ (0.00 ":irc.foonet.net 501 tester x :is not a recognised user mode.")
+ (0.04 ":tester!tester@10.0.2.100 MODE tester :+i")
+ (0.00 ":NickServ!NickServ@services.int NOTICE tester :This nickname is registered. Please choose a different nickname, or identify via \2/msg NickServ identify <password>\2."))
+
+((~privmsg 10 "PRIVMSG NickServ :IDENTIFY changeme")
+ (0.00 ":NickServ!NickServ@services.int NOTICE tester :You are now identified for \2tester\2.")
+ (0.01 ":irc.foonet.net 900 tester tester!tester@10.0.2.100 tester :You are now logged in as tester"))
+
+((~join 10 "JOIN #chan")
+ (0.00 ":tester!tester@10.0.2.100 JOIN :#chan")
+ (0.04 ":irc.foonet.net 353 tester = #chan :@alice bob tester")
+ (0.00 ":irc.foonet.net 366 tester #chan :End of /NAMES list."))
+
+((mode-b 10 "MODE #chan")
+ (0.03 ":irc.foonet.net 324 tester #chan :+nt")
+ (0.01 ":irc.foonet.net 329 tester #chan :1670229160")
+ (0.00 ":alice!alice@0::1 PRIVMSG #chan :tester, welcome!")
+ (0.00 ":bob!bob@0::1 PRIVMSG #chan :tester, welcome!")
+ (0.05 ":alice!alice@0::1 PRIVMSG #chan :bob: Thou art the cap of all the fools alive.")
+ (0.06 ":bob!bob@0::1 PRIVMSG #chan :alice: What, man! 'tis a night of revels; the gallants desire it."))
+
+((quit 10 "QUIT :\2ERC\2")
+ (0.1 ":tester!tester@10.0.2.100 QUIT :Client Quit"))
+
+((drop 1 DROP))