Re: bug#56514: 29.0.50; Improve ERC's URI scheme integration for irc:// links

From 2d35563e0ac22686bb69100536692cb026fc67f2 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <[email protected]>
Date: Fri, 11 Nov 2022 00:12:34 -0800
Subject: [PATCH 0/5] *** NOT A PATCH ***

*** BLURB HERE ***

F. Jason Park (5):
  Accommodate ircs:// URLs in url-irc and browse-url
  Refactor erc-select-read-args
  Default to TLS port when calling erc-tls from lisp
  Add optional server param to erc-networks--determine
  Improve new connections in erc-handle-irc-url

 doc/misc/erc.texi                             |  28 +++
 etc/NEWS                                      |  20 ++
 lisp/erc/erc-backend.el                       |   6 +
 lisp/erc/erc-compat.el                        |  19 ++
 lisp/erc/erc-networks.el                      |   9 +-
 lisp/erc/erc.el                               | 192 ++++++++++-----
 lisp/net/browse-url.el                        |  24 ++
 lisp/url/url-irc.el                           |  32 ++-
 test/lisp/erc/erc-networks-tests.el           |  17 ++
 test/lisp/erc/erc-scenarios-misc.el           |  28 +++
 test/lisp/erc/erc-tests.el                    | 226 ++++++++++++++++++
 .../lisp/erc/resources/join/legacy/foonet.eld |   2 +-
 test/lisp/net/browse-url-tests.el             |   9 +
 13 files changed, 537 insertions(+), 75 deletions(-)

Interdiff:
diff --git a/doc/misc/erc.texi b/doc/misc/erc.texi
index d01eab1bbb..9742fc3c22 100644
--- a/doc/misc/erc.texi
+++ b/doc/misc/erc.texi
@@ -998,10 +998,10 @@ Integrations
 
 @subheading URL
 For anything to work, you'll want to set @code{url-irc-function} to
-@code{url-irc-erc}.  As a rule of thumb, libraries that rely directly
-on @code{url-retrieve} should be good to go out the box from Emacs
-29.1 onward.  On older versions of Emacs, you may need to
-@code{(require 'erc)} beforehand. @pxref{Retrieving URLs,,, url, URL}.
+@code{url-irc-erc}.  As a rule of thumb, libraries relying directly on
+@code{url-retrieve} should be fine out the box from Emacs 29.1 onward.
+On older versions of Emacs, you may need to @code{(require 'erc)}
+beforehand. @pxref{Retrieving URLs,,, url, URL}.
 
 For other apps and libraries, such as those relying on the
 higher-level @code{browse-url}, you'll oftentimes be asked to specify
@@ -1012,22 +1012,11 @@ Integrations
 need a function as well:
 
 @lisp
-  '("\\birc6?s?://[][a-z0-9.,@@_:+%?&/#-]+"
-    0 t erc-browse-url-handler 0)
+  '("\\birc6?s?://[][a-z0-9.,@@_:+%?&/#-]+" 0 t browse-url-irc 0)
 @end lisp
 
-@defun erc-browse-url-handler url &rest args
-An autoloaded convenience function for use in options like those
-mentioned above.  @var{url} must be a string.  In Emacs 29 and above,
-the function @code{browse-url-irc} can be used instead.
-@end defun
-
 @noindent
-Keep in mind that when fiddling with these options, it may be easier
-(and more polite) to connect to a local server or a test network, like
-@samp{ircs://testnet.ergo.chat/#test}, since these generally don't
-require authentication.
-
+Users on Emacs 28 and below may need to use @code{browse-url} instead.
 
 @node Options
 @section Options
diff --git a/lisp/erc/erc-compat.el b/lisp/erc/erc-compat.el
index 683d19dfc7..340d90ba96 100644
--- a/lisp/erc/erc-compat.el
+++ b/lisp/erc/erc-compat.el
@@ -32,6 +32,7 @@
 ;;; Code:
 
 (require 'compat nil 'noerror)
+(eval-when-compile (require 'url-parse))
 
 ;;;###autoload(autoload 'erc-define-minor-mode "erc-compat")
 (define-obsolete-function-alias 'erc-define-minor-mode
@@ -168,20 +169,23 @@ erc-compat--with-memoization
     `(cl--generic-with-memoization ,table ,@forms))
    (t `(progn ,@forms))))
 
-(declare-function browse-url-irc "browse-url" (url &rest _))
+(defvar url-irc-function)
 
-(defun erc-compat--browse-url-irc (string &rest _)
-  "Parse STRING and call `url-irc'."
+(defun erc-compat--29-browse-url-irc (string &rest _)
+  (cl-assert (< emacs-major-version 29))
   (require 'url-irc)
-  (if (< emacs-major-version 29)
-      ;; `url-irc' binds this in Emacs 29+.
-      (let ((url-current-object (url-generic-parse-url string)))
-        (url-irc url-current-object))
-    (browse-url-irc string)))
+  (let* ((url (url-generic-parse-url string))
+         (url-irc-function
+          (if (function-equal url-irc-function 'url-irc-erc)
+              (lambda (host port chan user pass)
+                (erc-handle-irc-url host port chan user pass (url-type url)))
+            url-irc-function)))
+    (url-irc url)))
 
 (when (< emacs-major-version 29)
-  (add-to-list 'browse-url-default-handlers
-               '("\\`irc6?s?://" . erc-compat--browse-url-irc)))
+  (unless (assoc "\\`irc6?s?://" browse-url-default-handlers)
+    (push '("\\`irc6?s?://" . erc-compat--29-browse-url-irc)
+          browse-url-default-handlers)))
 
 (provide 'erc-compat)
 
diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 51a97c8de1..cfd1c34ef0 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -7195,7 +7195,7 @@ erc--url-default-connect-function
     (apply (if ircsp #'erc-tls #'erc) args)))
 
 ;;;###autoload
-(defun erc-handle-irc-url (host port channel nick password scheme)
+(defun erc-handle-irc-url (host port channel nick password &optional scheme)
   "Use ERC to IRC on HOST:PORT in CHANNEL.
 If ERC is already connected to HOST:PORT, simply /join CHANNEL.
 Otherwise, connect to HOST:PORT as NICK and /join CHANNEL.
@@ -7247,14 +7247,6 @@ erc-handle-irc-url
         (with-current-buffer server-buffer
           (erc-cmd-JOIN channel key))))))
 
-(defvar url-irc-function)
-
-;;;###autoload
-(defun erc-browse-url-handler (url &rest _)
-  "Launch an ERC session when given an irc:// URL."
-  (let ((url-irc-function 'url-irc-erc))
-    (erc-compat--browse-url-irc url)))
-
 (provide 'erc)
 
 ;;; erc.el ends here
diff --git a/test/lisp/erc/erc-scenarios-misc.el b/test/lisp/erc/erc-scenarios-misc.el
index ded620ccc1..8557a77906 100644
--- a/test/lisp/erc/erc-scenarios-misc.el
+++ b/test/lisp/erc/erc-scenarios-misc.el
@@ -177,4 +177,32 @@ erc-scenarios-dcc-chat-accept
         (erc-scenarios-common-say "Hi")
         (funcall expect 10 "Hola")))))
 
+(defvar url-irc-function)
+
+(ert-deftest erc-scenarios-handle-irc-url ()
+  :tags '(:expensive-test)
+  (erc-scenarios-common-with-cleanup
+      ((erc-scenarios-common-dialog "join/legacy")
+       (dumb-server (erc-d-run "localhost" t 'foonet))
+       (port (process-contact dumb-server :service))
+       (expect (erc-d-t-make-expecter))
+       (url-irc-function 'url-irc-erc)
+       (erc-url-connect-function
+        (lambda (scheme &rest r)
+          (ert-info ("Connect to foonet")
+            (should (equal scheme "irc"))
+            (with-current-buffer (apply #'erc `(:full-name "tester" ,@r))
+              (should (string= (buffer-name)
+                               (format "127.0.0.1:%d" port)))
+              (current-buffer))))))
+
+    (with-temp-buffer
+      (insert (format ";; irc://tester:[email protected]:%d/#chan" port))
+      (goto-char 10)
+      (browse-url-at-point))
+
+    (ert-info ("Connected")
+      (with-current-buffer (erc-d-t-wait-for 10 (get-buffer "#chan"))
+        (funcall expect 10 "welcome")))))
+
 ;;; erc-scenarios-misc.el ends here
diff --git a/test/lisp/erc/resources/join/legacy/foonet.eld b/test/lisp/erc/resources/join/legacy/foonet.eld
index 344ba7c1da..4025094a59 100644
--- a/test/lisp/erc/resources/join/legacy/foonet.eld
+++ b/test/lisp/erc/resources/join/legacy/foonet.eld
@@ -1,5 +1,5 @@
 ;; -*- mode: lisp-data; -*-
-((pass 1 "PASS :changeme"))
+((pass 10 "PASS :changeme"))
 ((nick 1 "NICK tester"))
 ((user 1 "USER user 0 * :tester")
  (0 ":irc.foonet.org 001 tester :Welcome to the foonet IRC Network tester")
-- 
2.38.1

From ee1c51c8f8309aa7f3761d71789be41c68a31591 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <[email protected]>
Date: Mon, 11 Jul 2022 05:14:57 -0700
Subject: [PATCH 1/5] Accommodate ircs:// URLs in url-irc and browse-url

* lisp/url/url-irc.el (url-irc-function): Change signature of function
interface to expect a final "scheme" argument, such as "ircs".
(url-irc): Call `url-irc-function' with new positional argument, the
scheme extracted via `url-type' from the input URL.
(url-irc-erc, url-irc-rcirc, url-irc-zenirc): Accept a URL scheme as a
sixth positional arg.
(url-ircs-default-port, url-ircs): Add new autoloaded constant and
alias for `url-scheme-get-property' to recognize.  Do this to avoid
having to add another file.
* lisp/net/browse-url.el (browse-url-irc-function): Add new option.
(browse-url--irc): Add new function to call `browse-url-irc-function'.
(browse-url-default-handlers): Add "irc://" entry.
(browse-url-irc): Add new function to serve as general handler for
"irc://" URLS.  Accept trailing variadic args to accommodate
non-browse-url interfaces as well.
* test/lisp/net/browse-url-tests.el
(browse-url-tests-select-handler-irc): Add test for "irc://" URL
pattern.
* etc/NEWS: Mention select browse-url and url-irc
changes.  (Bug#56514.)
---
 etc/NEWS                          | 20 +++++++++++++++++++
 lisp/net/browse-url.el            | 24 +++++++++++++++++++++++
 lisp/url/url-irc.el               | 32 ++++++++++++++++++++++++-------
 test/lisp/net/browse-url-tests.el |  9 +++++++++
 4 files changed, 78 insertions(+), 7 deletions(-)

diff --git a/etc/NEWS b/etc/NEWS
index ab64eff74e..500ac5e50b 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -438,6 +438,12 @@ The user options 'url-gateway-rlogin-host',
 'url-gateway-rlogin-parameters', and 'url-gateway-rlogin-user-name'
 are also obsolete.
 
+---
+** The user function 'url-irc-function' now takes a 'scheme' argument.
+The user option 'url-irc-function' is now called with a sixth argument
+corresponding to the scheme portion of the target URL.  For example,
+this would be "ircs" for a URL like "ircs://irc.libera.chat".
+
 ---
 ** The linum.el library is now obsolete.
 We recommend using either the built-in 'display-line-numbers-mode', or
@@ -2616,6 +2622,17 @@ This user option decides which URL scheme that 'browse-url' and
 related functions will use by default.  For example, you could
 customize this to "https" to always prefer HTTPS URLs.
 
+---
+*** New user option 'browse-url-irc-function'.
+This option specifies a function for opening irc:// links.  It
+defaults to the new function 'browse-url-irc'.
+
+---
+*** New function 'browse-url-irc'.
+This multipurpose autoloaded function can be used for opening irc://
+and ircs:// URLS by any caller that passes a URL string as an initial
+arg.
+
 ---
 *** Support for the Netscape web browser has been removed.
 This support has been obsolete since Emacs 25.1.  The final version of
@@ -2842,6 +2859,9 @@ remote host are shown.  Alternatively, the user option
 *** 'outlineify-sticky' command is renamed to 'allout-outlinify-sticky'.
 The old name is still available as an obsolete function alias.
 
+---
+*** The url-irc library now understands ircs:// links.
+
 ---
 *** New command 'world-clock-copy-time-as-kill' for 'M-x world-clock'.
 It copies the current line into the kill ring.
diff --git a/lisp/net/browse-url.el b/lisp/net/browse-url.el
index 1597f3651a..7ac6396d31 100644
--- a/lisp/net/browse-url.el
+++ b/lisp/net/browse-url.el
@@ -222,6 +222,14 @@ browse-url-man-function
           (function :tag "Other function"))
   :version "26.1")
 
+(defcustom browse-url-irc-function 'browse-url-irc
+  "Function to open an irc:// link."
+  :type '(choice
+          (function-item :tag "Emacs IRC" :value browse-url-irc)
+          (const :tag "None" nil)
+          (function :tag "Other function"))
+  :version "29.1")
+
 (defcustom browse-url-button-regexp
   (concat
    "\\b\\(\\(www\\.\\|\\(s?https?\\|ftp\\|file\\|gopher\\|gemini\\|"
@@ -547,6 +555,11 @@ browse-url--browser-kind-man
 (function-put 'browse-url--man 'browse-url-browser-kind
               #'browse-url--browser-kind-man)
 
+(defun browse-url--irc (url &rest args)
+  "Call `browse-url-irc-function' with URL and ARGS."
+  (funcall browse-url-irc-function url args))
+(function-put 'browse-url--irc 'browse-url-browser-kind 'internal)
+
 (defun browse-url--browser (url &rest args)
   "Call `browse-url-browser-function' with URL and ARGS."
   (funcall browse-url-browser-function url args))
@@ -565,6 +578,7 @@ browse-url--non-html-file-url-p
 (defvar browse-url-default-handlers
   '(("\\`mailto:" . browse-url--mailto)
     ("\\`man:" . browse-url--man)
+    ("\\`irc6?s?://" . browse-url--irc)
     (browse-url--non-html-file-url-p . browse-url-emacs))
   "Like `browse-url-handlers' but populated by Emacs and packages.
 
@@ -1510,6 +1524,16 @@ browse-url-text-emacs
 
 (function-put 'browse-url-text-emacs 'browse-url-browser-kind 'internal)
 
+;; --- irc ---
+
+;;;###autoload
+(defun browse-url-irc (url &rest _)
+  "Call `url-irc' directly after parsing URL.
+This function is a fit for options like `gnus-button-alist'."
+  (url-irc (url-generic-parse-url url)))
+
+(function-put 'browse-url-irc 'browse-url-browser-kind 'internal)
+
 ;; --- mailto ---
 
 (autoload 'rfc6068-parse-mailto-url "rfc6068")
diff --git a/lisp/url/url-irc.el b/lisp/url/url-irc.el
index 9161f7d13e..f97b6de6fe 100644
--- a/lisp/url/url-irc.el
+++ b/lisp/url/url-irc.el
@@ -38,11 +38,13 @@ url-irc-function
     PORT - the port number of the IRC server to contact
  CHANNEL - What channel on the server to visit right away (can be nil)
     USER - What username to use
-PASSWORD - What password to use"
+PASSWORD - What password to use.
+  SCHEME - a URI scheme, such as \"irc\" or \"ircs\""
   :type '(choice (const :tag "rcirc" :value url-irc-rcirc)
 		 (const :tag "ERC" :value url-irc-erc)
 		 (const :tag "ZEN IRC" :value url-irc-zenirc)
 		 (function :tag "Other"))
+  :version "29.1" ; Added SCHEME
   :group 'url)
 
 ;; External.
@@ -51,7 +53,7 @@ url-irc-function
 (defvar zenirc-server-alist)
 (defvar zenirc-buffer-name)
 
-(defun url-irc-zenirc (host port channel user password)
+(defun url-irc-zenirc (host port channel user password _)
   (let ((zenirc-buffer-name (if (and user host port)
 				(format "%s@%s:%d" user host port)
 			      (format "%s:%d" host port)))
@@ -65,14 +67,14 @@ url-irc-zenirc
       (insert "/join " channel)
       (zenirc-send-line))))
 
-(defun url-irc-rcirc (host port channel user password)
+(defun url-irc-rcirc (host port channel user password _)
   (let ((chan (when channel (concat "#" channel))))
     (rcirc-connect host port user nil nil (when chan (list chan)) password)
     (when chan
       (switch-to-buffer (concat chan "@" host)))))
 
-(defun url-irc-erc (host port channel user password)
-  (erc-handle-irc-url host port channel user password))
+(defun url-irc-erc (host port channel user password scheme)
+  (erc-handle-irc-url host port channel user password scheme))
 
 ;;;###autoload
 (defun url-irc (url)
@@ -80,16 +82,32 @@ url-irc
 	 (port (url-port url))
 	 (pass (url-password url))
 	 (user (url-user url))
-	 (chan (url-filename url)))
+         (chan (url-filename url))
+         (type (url-type url))
+         (compatp (eql 5 (cdr (func-arity url-irc-function)))))
     (if (url-target url)
 	(setq chan (concat chan "#" (url-target url))))
     (if (string-match "^/" chan)
 	(setq chan (substring chan 1 nil)))
     (if (= (length chan) 0)
 	(setq chan nil))
-    (funcall url-irc-function host port chan user pass)
+    (when compatp
+      (lwarn 'url :error "Obsolete value for `url-irc-function'"))
+    (apply url-irc-function
+           host port chan user pass (unless compatp (list type)))
     nil))
 
+;;;; ircs://
+
+;; The function `url-scheme-get-property' tries and fails to load the
+;; nonexistent url-ircs.el but falls back to using the following:
+
+;;;###autoload
+(defconst url-ircs-default-port 6697 "Default port for IRCS connections.")
+
+;;;###autoload
+(defalias 'url-ircs 'url-irc)
+
 (provide 'url-irc)
 
 ;;; url-irc.el ends here
diff --git a/test/lisp/net/browse-url-tests.el b/test/lisp/net/browse-url-tests.el
index 1c993958b8..dc81976821 100644
--- a/test/lisp/net/browse-url-tests.el
+++ b/test/lisp/net/browse-url-tests.el
@@ -56,6 +56,15 @@ browse-url-tests-select-handler-man
               'browse-url--man))
   (should-not (browse-url-select-handler "man:ls" 'external)))
 
+(ert-deftest browse-url-tests-select-handler-irc ()
+  (should (eq (browse-url-select-handler "irc://localhost" 'internal)
+              'browse-url--irc))
+  (should-not (browse-url-select-handler "irc://localhost" 'external))
+  (should (eq (browse-url-select-handler "irc6://localhost")
+              'browse-url--irc))
+  (should (eq (browse-url-select-handler "ircs://[email protected]/#chan")
+              'browse-url--irc)))
+
 (ert-deftest browse-url-tests-select-handler-file ()
   (should (eq (browse-url-select-handler "file://foo.txt")
               'browse-url-emacs))
-- 
2.38.1

From 3b6eeb91e25da87c33a0da6a4b768cbbc60d96d8 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <[email protected]>
Date: Mon, 11 Jul 2022 05:14:57 -0700
Subject: [PATCH 2/5] Refactor erc-select-read-args

* lisp/erc/erc-backend.el (erc--server-connect-dumb-ipv6-regexp): Add
liberal pattern for matching bracketed IPv6 addresses.
(erc-server-connect): Remove brackets from IPv6 hosts before
connecting.
* lisp/erc/erc.el (erc--ensure-url): Add compat adapter to massage
partial URLs given as input that may be missing the scheme:// portion.
(erc-select-read-args): Keep bracketed IPv6 hosts
intact.  Make this function fully URL-aware (was only partially so).
Accept optional `input' argument.
* lisp/erc/erc-tests.el (erc-tests--ipv6-examples,
erc--server-connect-dumb-ipv6-regexp, erc-select-read-args): Add test
reading user input during interactive invocations of entry points.
(Bug#56514.)
---
 lisp/erc/erc-backend.el    |  6 +++
 lisp/erc/erc.el            | 83 ++++++++++++++++++-----------------
 test/lisp/erc/erc-tests.el | 89 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 136 insertions(+), 42 deletions(-)

diff --git a/lisp/erc/erc-backend.el b/lisp/erc/erc-backend.el
index 026b34849a..1cb0876367 100644
--- a/lisp/erc/erc-backend.el
+++ b/lisp/erc/erc-backend.el
@@ -625,12 +625,18 @@ erc-open-network-stream
   (let ((p (plist-put parameters :nowait t)))
     (apply #'open-network-stream name buffer host service p)))
 
+(defvar erc--server-connect-dumb-ipv6-regexp
+  ;; Not for validation (gives false positives).
+  (rx bot "[" (group (+ (any xdigit digit ":.")) (? "%" (+ alnum))) "]" eot))
+
 (defun erc-server-connect (server port buffer &optional client-certificate)
   "Perform the connection and login using the specified SERVER and PORT.
 We will store server variables in the buffer given by BUFFER.
 CLIENT-CERTIFICATE may optionally be used to specify a TLS client
 certificate to use for authentication when connecting over
 TLS (see `erc-session-client-certificate' for more details)."
+  (when (string-match erc--server-connect-dumb-ipv6-regexp server)
+    (setq server (match-string 1 server)))
   (let ((msg (erc-format-message 'connect ?S server ?p port)) process
         (args `(,(format "erc-%s-%s" server port) nil ,server ,port)))
     (when client-certificate
diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 6b14cf87e2..7f25afa8c5 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -70,7 +70,7 @@
 (require 'auth-source)
 (require 'time-date)
 (require 'iso8601)
-(eval-when-compile (require 'subr-x))
+(eval-when-compile (require 'subr-x) (require 'url-parse))
 
 (defconst erc-version "5.4.1"
   "This version of ERC.")
@@ -2094,52 +2094,51 @@ erc-after-connect
   :group 'erc-hooks
   :type '(repeat function))
 
+(defun erc--ensure-url (input)
+  (unless (string-match (rx bot "irc" (? "6") (? "s") "://") input)
+    (when (and (string-match (rx (? (+ any) "@")
+                                 (or (group (* (not "[")) ":" (* any))
+                                     (+ any))
+                                 ":" (+ (not (any ":]"))) eot)
+                             input)
+               (match-beginning 1))
+      (setq input (concat "[" (substring input (match-beginning 1)) "]")))
+    (setq input (concat "irc://" input)))
+  input)
+
 ;;;###autoload
 (defun erc-select-read-args ()
   "Prompt the user for values of nick, server, port, and password."
-  (let (user-input server port nick passwd)
-    (setq user-input (read-string
-                      "IRC server: "
-                      (erc-compute-server) 'erc-server-history-list))
-
-    (if (string-match "\\(.*\\):\\(.*\\)\\'" user-input)
-        (setq port (erc-string-to-port (match-string 2 user-input))
-              user-input (match-string 1 user-input))
-      (setq port
-            (erc-string-to-port (read-string
-                                 "IRC port: " (erc-port-to-string
-                                               (erc-compute-port))))))
-
-    (if (string-match "\\`\\(.*\\)@\\(.*\\)" user-input)
-        (setq nick (match-string 1 user-input)
-              user-input (match-string 2 user-input))
-      (setq nick
-            (if (erc-already-logged-in server port nick)
-                (read-string
-                 (erc-format-message 'nick-in-use ?n nick)
-                 nick 'erc-nick-history-list)
-              (read-string
-               "Nickname: " (erc-compute-nick nick)
-               'erc-nick-history-list))))
-
-    (setq server user-input)
-
-    (setq passwd (if erc-prompt-for-password
-                     (read-passwd "Server password: ")
-                   (with-suppressed-warnings ((obsolete erc-password))
-                     erc-password)))
+  (require 'url-parse)
+  (let* ((input (let ((d (erc-compute-server)))
+                  (read-string (format "Server (default is %S): " d)
+                               nil 'erc-server-history-list d)))
+         ;; For legacy reasons, also accept a URL without a scheme.
+         (url (url-generic-parse-url (erc--ensure-url input)))
+         (server (url-host url))
+         (sp (and (or (string-suffix-p "s" (url-type url))
+                      (and (equal server erc-default-server)
+                           (not (string-prefix-p "irc://" input))))
+                  'ircs-u))
+         (port (or (url-portspec url)
+                   (erc-compute-port
+                    (let ((d (erc-compute-port sp))) ; may be a string
+                      (read-string (format "Port (default is %s): " d)
+                                   nil nil d)))))
+         ;; Trust the user not to connect twice accidentally.  We
+         ;; can't use `erc-already-logged-in' to check for an existing
+         ;; connection without modifying it to consider USER and PASS.
+         (nick (or (url-user url)
+                   (let ((d (erc-compute-nick)))
+                     (read-string (format "Nickname (default is %S): " d)
+                                  nil 'erc-nick-history-list d))))
+         (passwd (or (url-password url)
+                     (if erc-prompt-for-password
+                         (read-passwd "Server password (optional): ")
+                       (with-suppressed-warnings ((obsolete erc-password))
+                         erc-password)))))
     (when (and passwd (string= "" passwd))
       (setq passwd nil))
-
-    (while (erc-already-logged-in server port nick)
-      ;; hmm, this is a problem when using multiple connections to a bnc
-      ;; with the same nick. Currently this code prevents using more than one
-      ;; bnc with the same nick. actually it would be nice to have
-      ;; bncs transparent, so that erc-compute-buffer-name displays
-      ;; the server one is connected to.
-      (setq nick (read-string
-                  (erc-format-message 'nick-in-use ?n nick)
-                  nick 'erc-nick-history-list)))
     (list :server server :port port :nick nick :password passwd)))
 
 ;;;###autoload
diff --git a/test/lisp/erc/erc-tests.el b/test/lisp/erc/erc-tests.el
index c88dd9888d..f72db816af 100644
--- a/test/lisp/erc/erc-tests.el
+++ b/test/lisp/erc/erc-tests.el
@@ -953,4 +953,93 @@ erc-message
     (kill-buffer "ExampleNet")
     (kill-buffer "#chan")))
 
+(defvar erc-tests--ipv6-examples
+  '("1:2:3:4:5:6:7:8"
+    "::ffff:10.0.0.1" "::ffff:1.2.3.4" "::ffff:0.0.0.0"
+    "1:2:3:4:5:6:77:88" "::ffff:255.255.255.255"
+    "fe08::7:8" "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff"
+    "1:2:3:4:5:6:7:8" "1::" "1:2:3:4:5:6:7::" "1::8"
+    "1:2:3:4:5:6::8" "1:2:3:4:5:6::8" "1::7:8" "1:2:3:4:5::7:8"
+    "1:2:3:4:5::8" "1::6:7:8" "1:2:3:4::6:7:8" "1:2:3:4::8"
+    "1::5:6:7:8" "1:2:3::5:6:7:8" "1:2:3::8" "1::4:5:6:7:8"
+    "1:2::4:5:6:7:8" "1:2::8" "1::3:4:5:6:7:8" "1::3:4:5:6:7:8"
+    "1::8" "::2:3:4:5:6:7:8" "::2:3:4:5:6:7:8" "::8"
+    "::" "fe08::7:8%eth0" "fe08::7:8%1" "::255.255.255.255"
+    "::ffff:255.255.255.255" "::ffff:0:255.255.255.255"
+    "2001:db8:3:4::192.0.2.33" "64:ff9b::192.0.2.33"))
+
+(ert-deftest erc--server-connect-dumb-ipv6-regexp ()
+  (dolist (a erc-tests--ipv6-examples)
+    (should-not (string-match erc--server-connect-dumb-ipv6-regexp a))
+    (should (string-match erc--server-connect-dumb-ipv6-regexp
+                          (concat "[" a "]")))))
+
+(ert-deftest erc-select-read-args ()
+
+  (ert-info ("Defaults to TLS")
+    (should (equal (ert-simulate-keys "\r\r\r\r"
+                     (erc-select-read-args))
+                   (list :server "irc.libera.chat"
+                         :port 6697
+                         :nick (user-login-name)
+                         :password nil))))
+
+  (ert-info ("Override default TLS")
+    (should (equal (ert-simulate-keys "irc://irc.libera.chat\r\r\r\r"
+                     (erc-select-read-args))
+                   (list :server "irc.libera.chat"
+                         :port 6667
+                         :nick (user-login-name)
+                         :password nil))))
+
+  (ert-info ("Address includes port")
+    (should (equal (ert-simulate-keys
+                       "localhost:6667\rnick\r\r"
+                     (erc-select-read-args))
+                   (list :server "localhost"
+                         :port 6667
+                         :nick "nick"
+                         :password nil))))
+
+  (ert-info ("Address includes nick, password skipped via option")
+    (should (equal (ert-simulate-keys "nick@localhost:6667\r"
+                     (let (erc-prompt-for-password)
+                       (erc-select-read-args)))
+                   (list :server "localhost"
+                         :port 6667
+                         :nick "nick"
+                         :password nil))))
+
+  (ert-info ("Addresss includes nick and password")
+    (should (equal (ert-simulate-keys "nick:sesame@localhost:6667\r"
+                     (erc-select-read-args))
+                   (list :server "localhost"
+                         :port 6667
+                         :nick "nick"
+                         :password "sesame"))))
+
+  (ert-info ("IPv6 address plain")
+    (should (equal (ert-simulate-keys "::1\r\r\r\r"
+                     (erc-select-read-args))
+                   (list :server "[::1]"
+                         :port 6667
+                         :nick (user-login-name)
+                         :password nil))))
+
+  (ert-info ("IPv6 address with port")
+    (should (equal (ert-simulate-keys "[::1]:6667\r\r\r"
+                     (erc-select-read-args))
+                   (list :server "[::1]"
+                         :port 6667
+                         :nick (user-login-name)
+                         :password nil))))
+
+  (ert-info ("IPv6 address includes nick")
+    (should (equal (ert-simulate-keys "nick@[::1]:6667\r\r"
+                     (erc-select-read-args))
+                   (list :server "[::1]"
+                         :port 6667
+                         :nick "nick"
+                         :password nil)))))
+
 ;;; erc-tests.el ends here
-- 
2.38.1

From 6f3717e60b223090d84a198ee80c1d90ec7a0263 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <[email protected]>
Date: Mon, 11 Jul 2022 05:14:57 -0700
Subject: [PATCH 3/5] Default to TLS port when calling erc-tls from lisp

* lisp/erc/erc.el (erc-normalize-port): Add standard IANA port-name
mappings for 6667 and 6697.
(erc-open): Add note to doc string explaining that params `connect'
and `channel' are mutually exclusive.
(erc-tls): Call `erc-compute-port' with override.
(erc-compute-port): Call `erc-normalize-port' with result'.
* test/lisp/erc/erc-tests.el (erc-tls): Add simplistic test focusing
on default parameters.  (Bug#56514.)
---
 lisp/erc/erc.el            | 17 +++++++++++----
 test/lisp/erc/erc-tests.el | 42 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 4 deletions(-)

diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 7f25afa8c5..28370d7724 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -1542,6 +1542,11 @@ erc-normalize-port
 * ircs        -> 994
 * ircd        -> 6667
 * ircd-dalnet -> 7000"
+  ;; These were updated somewhat in 2022 to reflect modern standards
+  ;; and practices.  See also:
+  ;;
+  ;; https://datatracker.ietf.org/doc/html/rfc7194#section-1
+  ;; https://www.iana.org/assignments/service-names-port-numbers
   (cond
    ((symbolp port)
     (erc-normalize-port (symbol-name port)))
@@ -1554,8 +1559,10 @@ erc-normalize-port
         194)
        ((string-equal port "ircs")
         994)
-       ((string-equal port "ircd")
+       ((string-equal port "ircu") 6667) ; 6665-6669
+       ((string-equal port "ircd") ; nonstandard (irc-serv is 529)
         6667)
+       ((string-equal port "ircs-u") 6697)
        ((string-equal port "ircd-dalnet")
         7000)
        (t
@@ -1924,7 +1931,9 @@ erc-open
 
 If CONNECT is non-nil, connect to the server.  Otherwise assume
 already connected and just create a separate buffer for the new
-target CHANNEL.
+target given by CHANNEL, meaning these parameters are mutually
+exclusive.  Note that CHANNEL may also be a query; its name has
+been retained for historical reasons.
 
 Use PASSWD as user password on the server.  If TGT-LIST is
 non-nil, use it to initialize `erc-default-recipients'.
@@ -2183,7 +2192,7 @@ 'erc-ssl
 
 ;;;###autoload
 (cl-defun erc-tls (&key (server (erc-compute-server))
-                        (port   (erc-compute-port))
+                        (port   (erc-compute-port 'ircs-u))
                         (nick   (erc-compute-nick))
                         (user   (erc-compute-user))
                         password
@@ -6390,7 +6399,7 @@ erc-compute-port
 - PORT (the argument passed to this function)
 - The `erc-port' option
 - The `erc-default-port' variable"
-  (or port erc-port erc-default-port))
+  (erc-normalize-port (or port erc-port erc-default-port)))
 
 ;; time routines
 
diff --git a/test/lisp/erc/erc-tests.el b/test/lisp/erc/erc-tests.el
index f72db816af..db54cb4889 100644
--- a/test/lisp/erc/erc-tests.el
+++ b/test/lisp/erc/erc-tests.el
@@ -1042,4 +1042,46 @@ erc-select-read-args
                          :nick "nick"
                          :password nil)))))
 
+(ert-deftest erc-tls ()
+  (let (calls)
+    (cl-letf (((symbol-function 'user-login-name)
+               (lambda (&optional _) "tester"))
+              ((symbol-function 'erc-open)
+               (lambda (&rest r) (push r calls))))
+
+      (ert-info ("Defaults")
+        (erc-tls)
+        (should (equal (pop calls)
+                       '("irc.libera.chat" 6697 "tester" "unknown" t
+                         nil nil nil nil nil "user" nil))))
+
+      (ert-info ("Full")
+        (erc-tls :server "irc.gnu.org"
+                 :port 7000
+                 :user "bobo"
+                 :nick "bob"
+                 :full-name "Bob's Name"
+                 :password "bob:changeme"
+                 :client-certificate t
+                 :id 'GNU.org)
+        (should (equal (pop calls)
+                       '("irc.gnu.org" 7000 "bob" "Bob's Name" t
+                         "bob:changeme" nil nil nil t "bobo" GNU.org))))
+
+      ;; Values are often nil when called by lisp code, which leads to
+      ;; null params.  This is why `erc-open' recomputes almost
+      ;; everything.
+      (ert-info ("Fallback")
+        (let ((erc-nick "bob")
+              (erc-server "irc.gnu.org")
+              (erc-email-userid "bobo")
+              (erc-user-full-name "Bob's Name"))
+          (erc-tls :server nil
+                   :port 7000
+                   :nick nil
+                   :password "bob:changeme"))
+        (should (equal (pop calls)
+                       '(nil 7000 nil "Bob's Name" t
+                             "bob:changeme" nil nil nil nil "bobo" nil)))))))
+
 ;;; erc-tests.el ends here
-- 
2.38.1

From 960c1ec9f753a9c61f6353c12a8e616bd4121ca5 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <[email protected]>
Date: Mon, 11 Jul 2022 05:14:57 -0700
Subject: [PATCH 4/5] Add optional server param to erc-networks--determine

* lisp/erc/erc-networks.el (erc-networks--determine): Accept optional
`server' argument.
* test/lisp/erc/erc-networks-tests.el (erc-networks--determine): Add
test.  (Bug#56514.)
---
 lisp/erc/erc-networks.el            |  9 +++++----
 test/lisp/erc/erc-networks-tests.el | 17 +++++++++++++++++
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/lisp/erc/erc-networks.el b/lisp/erc/erc-networks.el
index dba6ead073..b3e5fcf1a3 100644
--- a/lisp/erc/erc-networks.el
+++ b/lisp/erc/erc-networks.el
@@ -1256,14 +1256,15 @@ erc-set-network-name
 (defconst erc-networks--name-missing-sentinel (gensym "Unknown ")
   "Value to cover rare case of a literal NETWORK=nil.")
 
-(defun erc-networks--determine ()
+(defun erc-networks--determine (&optional server)
   "Return the name of the network as a symbol.
-Search `erc-networks-alist' for a known entity matching
+Search `erc-networks-alist' for a known entity matching SERVER or
 `erc-server-announced-name'.  If that fails, use the display name
 given by the `RPL_ISUPPORT' NETWORK parameter."
   (or (cl-loop for (name matcher) in erc-networks-alist
-               when (and matcher (string-match (concat matcher "\\'")
-                                               erc-server-announced-name))
+               when (and matcher
+                         (string-match (concat matcher "\\'")
+                                       (or server erc-server-announced-name)))
                return name)
       (and-let* ((vanity (erc--get-isupport-entry 'NETWORK 'single))
                  ((intern vanity))))
diff --git a/test/lisp/erc/erc-networks-tests.el b/test/lisp/erc/erc-networks-tests.el
index 32bdfa11ff..fc12bf7ce3 100644
--- a/test/lisp/erc/erc-networks-tests.el
+++ b/test/lisp/erc/erc-networks-tests.el
@@ -1704,4 +1704,21 @@ erc-networks--update-server-identity--triple-new
 
   (erc-networks-tests--clean-bufs))
 
+(ert-deftest erc-networks--determine ()
+  (should (eq (erc-networks--determine "irc.libera.chat") 'Libera.Chat))
+  (should (eq (erc-networks--determine "irc.oftc.net") 'OFTC))
+  (should (eq (erc-networks--determine "irc.dal.net") 'DALnet))
+
+  (let ((erc-server-announced-name "zirconium.libera.chat"))
+    (should (eq (erc-networks--determine) 'Libera.Chat)))
+  (let ((erc-server-announced-name "weber.oftc.net"))
+    (should (eq (erc-networks--determine) 'OFTC)))
+  (let ((erc-server-announced-name "redemption.ix.us.dal.net"))
+    (should (eq (erc-networks--determine) 'DALnet)))
+
+  ;; Failure
+  (let ((erc-server-announced-name "irc-us2.alphachat.net"))
+    (should (eq (erc-networks--determine)
+                erc-networks--name-missing-sentinel))))
+
 ;;; erc-networks-tests.el ends here
-- 
2.38.1

From 2d35563e0ac22686bb69100536692cb026fc67f2 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <[email protected]>
Date: Mon, 11 Jul 2022 05:14:57 -0700
Subject: [PATCH 5/5] Improve new connections in erc-handle-irc-url

* lisp/erc/erc.el (erc-handle-irc-url): Add optional "scheme"
parameter.  Fix `erc-open' invocation so that the server buffer is
named correctly by deferring to a new customizable opener.  Arrange
for JOINing a channel in a manner similar to ERC's autojoin module.
(erc-url-connect-function): Add new option for creating a new ERC
connection based on info parsed from a URL.
(erc--url-default-connect-function): New function to serve as an
interactive-only fallback when a user hasn't specified a URL connect
function.
* lisp/erc/erc-compat.el (erc-compat--29-browse-url--irc): Add new
compatibility function for `browse-url-irc' and add it to
`browse-url-default-handlers' on Emacs versions below 29.
* lisp/erc/erc-tests.el (erc-tests--make-server-buf,
erc-tests--make-client-buf): Add helpers for creating dummy ERC
buffers.
(erc-handle-irc-url): Add test.
* test/lisp/erc/erc-scenarios-misc.el (erc-scenarios-handle-irc-url):
Add new test.
* test/lisp/erc/resources/join/legacy/foonet.eld: Relax
timeout.  (Bug#56514.)
---
 doc/misc/erc.texi                             | 28 ++++++
 lisp/erc/erc-compat.el                        | 19 ++++
 lisp/erc/erc.el                               | 92 ++++++++++++++----
 test/lisp/erc/erc-scenarios-misc.el           | 28 ++++++
 test/lisp/erc/erc-tests.el                    | 95 +++++++++++++++++++
 .../lisp/erc/resources/join/legacy/foonet.eld |  2 +-
 6 files changed, 246 insertions(+), 18 deletions(-)

diff --git a/doc/misc/erc.texi b/doc/misc/erc.texi
index 3db83197f9..9742fc3c22 100644
--- a/doc/misc/erc.texi
+++ b/doc/misc/erc.texi
@@ -79,6 +79,7 @@ Top
 
 * Connecting::                  Ways of connecting to an IRC server.
 * Sample Configuration::        An example configuration file.
+* Integrations::                Integrations available for ERC.
 * Options::                     Options that are available for ERC.
 
 @end detailmenu
@@ -526,6 +527,7 @@ Advanced Usage
 @menu
 * Connecting::                  Ways of connecting to an IRC server.
 * Sample Configuration::        An example configuration file.
+* Integrations::                Integrations available for ERC.
 * Options::                     Options that are available for ERC.
 @end menu
 
@@ -990,6 +992,32 @@ Sample Configuration
 ;; (setq erc-kill-server-buffer-on-quit t)
 @end lisp
 
+@node Integrations
+@section Integrations
+@cindex integrations
+
+@subheading URL
+For anything to work, you'll want to set @code{url-irc-function} to
+@code{url-irc-erc}.  As a rule of thumb, libraries relying directly on
+@code{url-retrieve} should be fine out the box from Emacs 29.1 onward.
+On older versions of Emacs, you may need to @code{(require 'erc)}
+beforehand. @pxref{Retrieving URLs,,, url, URL}.
+
+For other apps and libraries, such as those relying on the
+higher-level @code{browse-url}, you'll oftentimes be asked to specify
+a pattern, sometimes paired with a function that accepts a string URL
+as a first argument.  For example, with EWW, you may need to tack
+something like @code{"\\|\\`irc6?s?:"} onto the end of
+@code{eww-use-browse-url}.  But with @code{gnus-button-alist}, you'll
+need a function as well:
+
+@lisp
+  '("\\birc6?s?://[][a-z0-9.,@@_:+%?&/#-]+" 0 t browse-url-irc 0)
+@end lisp
+
+@noindent
+Users on Emacs 28 and below may need to use @code{browse-url} instead.
+
 @node Options
 @section Options
 @cindex options
diff --git a/lisp/erc/erc-compat.el b/lisp/erc/erc-compat.el
index 03bd8f1352..340d90ba96 100644
--- a/lisp/erc/erc-compat.el
+++ b/lisp/erc/erc-compat.el
@@ -32,6 +32,7 @@
 ;;; Code:
 
 (require 'compat nil 'noerror)
+(eval-when-compile (require 'url-parse))
 
 ;;;###autoload(autoload 'erc-define-minor-mode "erc-compat")
 (define-obsolete-function-alias 'erc-define-minor-mode
@@ -168,6 +169,24 @@ erc-compat--with-memoization
     `(cl--generic-with-memoization ,table ,@forms))
    (t `(progn ,@forms))))
 
+(defvar url-irc-function)
+
+(defun erc-compat--29-browse-url-irc (string &rest _)
+  (cl-assert (< emacs-major-version 29))
+  (require 'url-irc)
+  (let* ((url (url-generic-parse-url string))
+         (url-irc-function
+          (if (function-equal url-irc-function 'url-irc-erc)
+              (lambda (host port chan user pass)
+                (erc-handle-irc-url host port chan user pass (url-type url)))
+            url-irc-function)))
+    (url-irc url)))
+
+(when (< emacs-major-version 29)
+  (unless (assoc "\\`irc6?s?://" browse-url-default-handlers)
+    (push '("\\`irc6?s?://" . erc-compat--29-browse-url-irc)
+          browse-url-default-handlers)))
+
 (provide 'erc-compat)
 
 ;;; erc-compat.el ends here
diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 28370d7724..cfd1c34ef0 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -7169,25 +7169,83 @@ erc-get-parsed-vector-type
 ;; Teach url.el how to open irc:// URLs with ERC.
 ;; To activate, customize `url-irc-function' to `url-irc-erc'.
 
-;; FIXME change user to nick, and use API to find server buffer
+(defcustom erc-url-connect-function nil
+  "When non-nil, a function used to connect to an IRC URL.
+Called with a string meant to represent a URL scheme, like
+\"ircs\", followed by any number of keyword arguments recognized
+by `erc' and `erc-tls'."
+  :group 'erc
+  :package-version '(ERC . "5.4.1") ; FIXME increment on release
+  :type '(choice (const nil) function))
+
+(defun erc--url-default-connect-function (scheme &rest plist)
+  (let* ((ircsp (if scheme
+                    (string-suffix-p "s" scheme)
+                  (or (eql 6697 (plist-get plist :port))
+                      (yes-or-no-p "Connect using TLS? "))))
+         (erc-server (plist-get plist :server))
+         (erc-port (or (plist-get plist :port)
+                       (and ircsp (erc-normalize-port 'ircs-u))
+                       erc-port))
+         (erc-nick (or (plist-get plist :nick) erc-nick))
+         (erc-password (plist-get plist :password))
+         (args (erc-select-read-args)))
+    (unless ircsp
+      (setq ircsp (eql 6697 erc-port)))
+    (apply (if ircsp #'erc-tls #'erc) args)))
+
 ;;;###autoload
-(defun erc-handle-irc-url (host port channel user password)
-  "Use ERC to IRC on HOST:PORT in CHANNEL as USER with PASSWORD.
+(defun erc-handle-irc-url (host port channel nick password &optional scheme)
+  "Use ERC to IRC on HOST:PORT in CHANNEL.
 If ERC is already connected to HOST:PORT, simply /join CHANNEL.
-Otherwise, connect to HOST:PORT as USER and /join CHANNEL."
-  (let ((server-buffer
-         (car (erc-buffer-filter
-               (lambda ()
-                 (and (string-equal erc-session-server host)
-                      (= erc-session-port port)
-                      (erc-open-server-buffer-p)))))))
-    (with-current-buffer (or server-buffer (current-buffer))
-      (if (and server-buffer channel)
-          (erc-cmd-JOIN channel)
-        (erc-open host port (or user (erc-compute-nick)) (erc-compute-full-name)
-                  (not server-buffer) password nil channel
-                  (when server-buffer
-                    (get-buffer-process server-buffer)))))))
+Otherwise, connect to HOST:PORT as NICK and /join CHANNEL.
+
+Beginning with ERC 5.5, new connections require human intervention.
+Customize `erc-url-connect-function' to override this."
+  (when (eql port 0) (setq port nil))
+  (let* ((net (erc-networks--determine host))
+         (server-buffer
+          ;; Viable matches may slip through the cracks for unknown
+          ;; networks.  Additional passes could likely improve things.
+          (car (erc-buffer-filter
+                (lambda ()
+                  (and (not erc--target)
+                       (erc-server-process-alive)
+                       ;; Always trust a matched network.
+                       (or (and net (eq net (erc-network)))
+                           (and (string-equal erc-session-server host)
+                                ;; Ports only matter when dialed hosts
+                                ;; match and we have sufficient info.
+                                (or (not port)
+                                    (= (erc-normalize-port erc-session-port)
+                                       port)))))))))
+         key deferred)
+    (unless server-buffer
+      (setq deferred t
+            server-buffer (apply (or erc-url-connect-function
+                                     #'erc--url-default-connect-function)
+                                 scheme
+                                 :server host
+                                 `(,@(and port (list :port port))
+                                   ,@(and nick (list :nick nick))
+                                   ,@(and password `(:password ,password))))))
+    (when channel
+      ;; These aren't percent-decoded by default
+      (when (string-prefix-p "%" channel)
+        (setq channel (url-unhex-string channel)))
+      (cl-multiple-value-setq (channel key) (split-string channel "[?]"))
+      (if deferred
+          ;; Alternatively, we could make this a defmethod, so when
+          ;; autojoin is loaded, it can do its own thing.  Also, as
+          ;; with `erc-once-with-server-event', it's fine to set local
+          ;; hooks here because they're killed when reconnecting.
+          (with-current-buffer server-buffer
+            (letrec ((f (lambda (&rest _)
+                          (remove-hook 'erc-after-connect f t)
+                          (erc-cmd-JOIN channel key))))
+              (add-hook 'erc-after-connect f nil t)))
+        (with-current-buffer server-buffer
+          (erc-cmd-JOIN channel key))))))
 
 (provide 'erc)
 
diff --git a/test/lisp/erc/erc-scenarios-misc.el b/test/lisp/erc/erc-scenarios-misc.el
index ded620ccc1..8557a77906 100644
--- a/test/lisp/erc/erc-scenarios-misc.el
+++ b/test/lisp/erc/erc-scenarios-misc.el
@@ -177,4 +177,32 @@ erc-scenarios-dcc-chat-accept
         (erc-scenarios-common-say "Hi")
         (funcall expect 10 "Hola")))))
 
+(defvar url-irc-function)
+
+(ert-deftest erc-scenarios-handle-irc-url ()
+  :tags '(:expensive-test)
+  (erc-scenarios-common-with-cleanup
+      ((erc-scenarios-common-dialog "join/legacy")
+       (dumb-server (erc-d-run "localhost" t 'foonet))
+       (port (process-contact dumb-server :service))
+       (expect (erc-d-t-make-expecter))
+       (url-irc-function 'url-irc-erc)
+       (erc-url-connect-function
+        (lambda (scheme &rest r)
+          (ert-info ("Connect to foonet")
+            (should (equal scheme "irc"))
+            (with-current-buffer (apply #'erc `(:full-name "tester" ,@r))
+              (should (string= (buffer-name)
+                               (format "127.0.0.1:%d" port)))
+              (current-buffer))))))
+
+    (with-temp-buffer
+      (insert (format ";; irc://tester:[email protected]:%d/#chan" port))
+      (goto-char 10)
+      (browse-url-at-point))
+
+    (ert-info ("Connected")
+      (with-current-buffer (erc-d-t-wait-for 10 (get-buffer "#chan"))
+        (funcall expect 10 "welcome")))))
+
 ;;; erc-scenarios-misc.el ends here
diff --git a/test/lisp/erc/erc-tests.el b/test/lisp/erc/erc-tests.el
index db54cb4889..f83e8c8717 100644
--- a/test/lisp/erc/erc-tests.el
+++ b/test/lisp/erc/erc-tests.el
@@ -1084,4 +1084,99 @@ erc-tls
                        '(nil 7000 nil "Bob's Name" t
                              "bob:changeme" nil nil nil nil "bobo" nil)))))))
 
+(defun erc-tests--make-server-buf (name)
+  (with-current-buffer (get-buffer-create name)
+    (erc-mode)
+    (setq erc-server-process (start-process "sleep" (current-buffer)
+                                            "sleep" "1")
+          erc-session-server (concat "irc." name ".org")
+          erc-session-port 6667
+          erc-network (intern name))
+    (set-process-query-on-exit-flag erc-server-process nil)
+    (current-buffer)))
+
+(defun erc-tests--make-client-buf (server name)
+  (unless (bufferp server)
+    (setq server (get-buffer server)))
+  (with-current-buffer (get-buffer-create name)
+    (erc-mode)
+    (setq erc--target (erc--target-from-string name))
+    (dolist (v '(erc-server-process
+                 erc-session-server
+                 erc-session-port
+                 erc-network))
+      (set v (buffer-local-value v server)))
+    (current-buffer)))
+
+(ert-deftest erc-handle-irc-url ()
+  (let* (calls
+         rvbuf
+         erc-networks-alist
+         erc-kill-channel-hook erc-kill-server-hook erc-kill-buffer-hook
+         (erc-url-connect-function
+          (lambda (&rest r)
+            (push r calls)
+            (if (functionp rvbuf) (funcall rvbuf) rvbuf))))
+
+    (cl-letf (((symbol-function 'erc-cmd-JOIN)
+               (lambda (&rest r) (push r calls))))
+
+      (with-current-buffer (erc-tests--make-server-buf "foonet")
+        (setq rvbuf (current-buffer)))
+      (erc-tests--make-server-buf "barnet")
+      (erc-tests--make-server-buf "baznet")
+
+      (ert-info ("Unknown network")
+        (erc-handle-irc-url "irc.foonet.org" 6667 "#chan" nil nil "irc")
+        (should (equal '("#chan" nil) (pop calls)))
+        (should-not calls))
+
+      (ert-info ("Unknown network, no port")
+        (erc-handle-irc-url "irc.foonet.org" nil "#chan" nil nil "irc")
+        (should (equal '("#chan" nil) (pop calls)))
+        (should-not calls))
+
+      (ert-info ("Known network, no port")
+        (setq erc-networks-alist '((foonet "irc.foonet.org")))
+        (erc-handle-irc-url "irc.foonet.org" nil "#chan" nil nil "irc")
+        (should (equal '("#chan" nil) (pop calls)))
+        (should-not calls))
+
+      (ert-info ("Known network, different port")
+        (erc-handle-irc-url "irc.foonet.org" 6697 "#chan" nil nil "irc")
+        (should (equal '("#chan" nil) (pop calls)))
+        (should-not calls))
+
+      (ert-info ("Known network, existing chan with key")
+        (erc-tests--make-client-buf "foonet" "#chan")
+        (erc-handle-irc-url "irc.foonet.org" nil "#chan?sec" nil nil "irc")
+        (should (equal '("#chan" "sec") (pop calls)))
+        (should-not calls))
+
+      (ert-info ("Unknown network, connect, no chan")
+        (erc-handle-irc-url "irc.gnu.org" nil nil nil nil "irc")
+        (should (equal '("irc" :server "irc.gnu.org") (pop calls)))
+        (should-not calls))
+
+      (ert-info ("Unknown network, connect, chan")
+        (with-current-buffer "foonet"
+          (should-not (local-variable-p 'erc-after-connect)))
+        (setq rvbuf (lambda () (erc-tests--make-server-buf "gnu")))
+        (erc-handle-irc-url "irc.gnu.org" nil "#spam" nil nil "irc")
+        (should (equal '("irc" :server "irc.gnu.org") (pop calls)))
+        (should-not calls)
+        (with-current-buffer "gnu"
+          (should (local-variable-p 'erc-after-connect))
+          (funcall (car erc-after-connect))
+          (should (equal '("#spam" nil) (pop calls)))
+          (should-not erc-after-connect)
+          (should-not (local-variable-p 'erc-after-connect)))
+        (should-not calls))))
+
+  (when noninteractive
+    (kill-buffer "foonet")
+    (kill-buffer "barnet")
+    (kill-buffer "baznet")
+    (kill-buffer "#chan")))
+
 ;;; erc-tests.el ends here
diff --git a/test/lisp/erc/resources/join/legacy/foonet.eld b/test/lisp/erc/resources/join/legacy/foonet.eld
index 344ba7c1da..4025094a59 100644
--- a/test/lisp/erc/resources/join/legacy/foonet.eld
+++ b/test/lisp/erc/resources/join/legacy/foonet.eld
@@ -1,5 +1,5 @@
 ;; -*- mode: lisp-data; -*-
-((pass 1 "PASS :changeme"))
+((pass 10 "PASS :changeme"))
 ((nick 1 "NICK tester"))
 ((user 1 "USER user 0 * :tester")
  (0 ":irc.foonet.org 001 tester :Welcome to the foonet IRC Network tester")
-- 
2.38.1