Don't send erc-sasl-user as USER command argument

* lisp/erc/erc-sasl.el (erc-sasl--send-cap-ls): Add internal switch
for sending an opening "CAP LS".  The rationale for not enabling this
by default is twofold: one, it more strongly implies that ERC supports
IRCv3 client capability negotiation, which is somewhat disingenuous;
and, two, We'd still be "faking it" by firing and forgetting, and more
balls in the air makes things less predictable.
(erc--register-connection): Possibly send a "CAP LS" before anything
depending on the value of `erc-sasl--send-cap-ls'.  Also, don't
attempt to send `erc-session-username' when it holds an SASL username
because the latter may contain protocol-defying characters.
* test/lisp/erc/resources/base/local-modules/fourth.eld: change user
parameter of "USER" command to reflect nick when `erc-sasl-user' is
set to `:user'.  (Bug#59976.)

2 files changed, 20 insertions, 7 deletions

diff --git a/lisp/erc/erc-sasl.el b/lisp/erc/erc-sasl.el
index 280910111d5..78d02a46381 100644
--- a/lisp/erc/erc-sasl.el
+++ b/lisp/erc/erc-sasl.el
@@ -414,17 +414,30 @@ This doesn't solicit or validate a suite of supported mechanisms."
                                        " "))
   (erc-sasl--destroy proc))
 
+(defvar erc-sasl--send-cap-ls nil
+  "Whether to send an opening \"CAP LS\" command.
+This is an escape hatch for picky servers.  If you need it turned
+into a user option, please let ERC know via \\[erc-bug].
+Otherwise, expect it to disappear in subsequent versions.")
+
 (cl-defmethod erc--register-connection (&context (erc-sasl-mode (eql t)))
-  "Send speculative/pipelined CAP and AUTHENTICATE and hope for the best."
+  "Send speculative CAP and pipelined AUTHENTICATE and hope for the best."
   (if-let* ((c (erc-sasl--state-client erc-sasl--state))
             (m (sasl-mechanism-name (sasl-client-mechanism c))))
       (progn
-        (erc-server-send "CAP REQ :sasl")
-        (if (and erc-session-password
-                 (eq :password (alist-get 'password erc-sasl--options)))
-            (let (erc-session-password)
-              (erc-login))
+        (erc-server-send (if erc-sasl--send-cap-ls "CAP LS" "CAP REQ :sasl"))
+        (let ((erc-session-password
+               (and erc-session-password
+                    (not (eq :password (alist-get 'password erc-sasl--options)))
+                    erc-session-password))
+              (erc-session-username
+               ;; The username may contain a colon or a space
+               (if (eq :user (alist-get 'user erc-sasl--options))
+                   (erc-current-nick)
+                 erc-session-username)))
           (erc-login))
+        (when erc-sasl--send-cap-ls
+          (erc-server-send "CAP REQ :sasl"))
         (erc-server-send (format "AUTHENTICATE %s" m)))
     (erc-sasl--destroy erc-server-process)))
 
diff --git a/test/lisp/erc/resources/base/local-modules/fourth.eld b/test/lisp/erc/resources/base/local-modules/fourth.eld
index fd6d62b6cc2..4ac5dcbd38b 100644
--- a/test/lisp/erc/resources/base/local-modules/fourth.eld
+++ b/test/lisp/erc/resources/base/local-modules/fourth.eld
@@ -1,7 +1,7 @@
 ;; -*- mode: lisp-data; -*-
 ((cap 10 "CAP REQ :sasl"))
 ((nick 10 "NICK tester`"))
-((user 10 "USER tester 0 * :tester"))
+((user 10 "USER tester` 0 * :tester"))
 
 ((authenticate 10 "AUTHENTICATE PLAIN")
  (0.0 ":irc.foonet.org CAP * ACK sasl")