* lisp/erc/erc-button.el
(erc-button--display-error-notice-with-keys-and-warn): Use
`erc--lwarn' so the warnings buffer is overridable for testing.
* lisp/erc/erc-sasl.el (erc-sasl-mode, erc-sasl-enable): Signal an
`error' instead of calling `erc-error', which continues execution.  In
this special case, the session cannot continue initializing, since
connection registration can't reasonably be expected to complete
successfully.
(erc-sasl--destroy): Don't run `erc-quit-hook', and issue a warning of
level `:error' to get users' attention instead of calling `ding'.
* lisp/erc/erc-speedbar.el
(erc-speedbar--emulate-sidebar-set-window-preserve-size): Don't set
window parameters.  Doing this basically made
`erc-speedbar-toggle-nicknames-window-lock' unusable.
(erc-speedbar--toggle-nicknames-sidebar): Manually unlock the window
after toggling.
(erc-nickbar-mode, erc-nickbar-enable, erc-nickbar-disable): Don't
`ding' when called in a non-ERC buffer, and make sure to call
`erc-speedbar--ensure' from an ERC buffer.  Also, don't disable
minor-mode var when speedbar buffer doesn't exist because that doesn't
ensure it'll be created the next time around, and users may count on
the activation state remaining consistent.
(erc-speedbar-toggle-nicknames-window-lock): Make usable from lisp
with explicit numeric arg.
* lisp/erc/erc-status-sidebar.el (erc-bufbar-mode, erc-bufbar-enable):
Only create the side window from an erc-mode buffer to ensure the
ratio is preserved when burying the current buffer, e.g., with
`custom-buffer-done'.
* lisp/erc/erc.el (erc--warnings-buffer-name, erc--lwarn): New
function, an analog of `lwarn', that allows for overriding the
warnings buffer with the new variable `erc--warnings-buffer-name'.
(erc-cmd-SERVER): Add comment.
* test/lisp/erc/erc-scenarios-sasl.el
(erc-scenarios-sasl--plain-fail): Expect warning instead of error.
* test/lisp/erc/erc-scenarios-status-sidebar.el
(erc-scenarios-status-sidebar--bufbar): Refresh when interactive as
well.
* test/lisp/erc/resources/sasl/plain-failed.eld: Expect EOF instead of
"CAP END".  (Bug#63595)

* lisp/erc/erc.el (erc--insert-marker): New internal variable for
overriding `erc-insert-marker' when displaying messages at a
non-default location in the buffer.
(erc-display-line-1): Favor `erc--insert-marker' over
`erc-insert-marker' when non-nil.
; * test/lisp/erc/resources/base/assoc/multi-net/barnet.eld: Timeouts.
; * test/lisp/erc/resources/base/assoc/multi-net/foonet.eld: Timeouts.
; * test/lisp/erc/resources/base/netid/bouncer/barnet-drop.eld: Timeouts.
; * test/lisp/erc/resources/base/netid/bouncer/foonet-drop.eld: Timeouts.
; * test/lisp/erc/resources/erc-d/resources/dynamic-foonet.eld: Timeouts.
; * test/lisp/erc/resources/sasl/scram-sha-1.eld: Timeouts.
; * test/lisp/erc/resources/sasl/scram-sha-256.eld: Timeouts.

* lisp/erc/erc-sasl.el: (erc-server-AUTHENTICATE): Account for
client messages exceeding 400 bytes.  (Bug#62421.)
* test/lisp/erc/erc-scenarios-sasl.el
(erc-scenarios-sasl--plain-overlong-split,
erc-scenarios-sasl--plain-overlong-aligned): Add tests.
* test/lisp/erc/resources/sasl/plain-overlong-aligned.eld: New file.
* test/lisp/erc/resources/sasl/plain-overlong-split.eld: New file.

* doc/misc/erc.texi: Add SASL section in Advanced Usage chapter to
document the new SASL module.

* etc/ERC-NEWS: Mention addition of erc-sasl module for SASL support.

* lisp/erc/erc-compat.el
(erc-compat--29-sasl-scram-construct-gs2-header,
erc-compat--29-sasl-scram-client-first-message,
erc-compat--29-sasl-scram--client-final-message): Fix encoding bug and
add minimal authorization support with copies of SASL functions
introduced in Emacs 29.

* lisp/erc/erc.el (erc-modules): Add `sasl'.
* lisp/erc/erc-sasl.el: New file (bug#29108).
* test/lisp/erc/erc-sasl-tests.el: New file.
* test/lisp/erc/erc-scenarios-sasl.el: New file.
* test/lisp/erc/resources/sasl/plain-failed.eld: New file.
* test/lisp/erc/resources/sasl/plain.eld: New file.
* test/lisp/erc/resources/sasl/scram-sha-1.eld: New file.
* test/lisp/erc/resources/sasl/scram-sha-256.eld: New file.
* test/lisp/erc/resources/sasl/external.eld: New file.