master c96a626dce2 1/4: Allow login to contain NUH delimiters in erc-parse-user

[F. Jason Park]

branch: master
commit c96a626dce2a12d1415e0d2c6e9eaeac8c5a1d75
Author: F. Jason Park <jp@neverwas.me>
Commit: F. Jason Park <jp@neverwas.me>

    Allow login to contain NUH delimiters in erc-parse-user
    
    * lisp/erc/erc.el (erc--parse-user-regexp-legacy,
    erc--parse-user-regexp-pedantic): New constants.  The first is the
    original pattern that matches across line endings.  The second
    disallows multiline strings and interprets excess delimiting
    characters as part of the middle, "user" component as per RFC1459.
    The latter distinction is largely academic because most servers reject
    such logins anyway, but bridges to other protocols and future
    extensions may need to exploit this for novel uses.
    (erc--parse-user-regexp): New variable, currently set to
    `erc--parse-user-regexp-legacy'.
    (erc-parse-user): Keep original pattern as default, but do so
    indirectly via `erc--parse-user-regexp'.
    * test/lisp/erc/erc-tests.el (erc-parse-user): New test.
---
 lisp/erc/erc.el            | 12 +++++++++++-
 test/lisp/erc/erc-tests.el | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 7375b5308ea..f7237c9e334 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -6316,12 +6316,22 @@ EmacsSpeak support."
 
 (defalias 'erc-list 'ensure-list)
 
+(defconst erc--parse-user-regexp-pedantic
+  (rx bot (group (* (not (any "!\r\n"))))
+      "!" (group (* nonl))
+      "@" (group (* nonl)) eot))
+
+(defconst erc--parse-user-regexp-legacy
+  "^\\([^!\n]*\\)!\\([^@\n]*\\)@\\(.*\\)$")
+
+(defvar erc--parse-user-regexp erc--parse-user-regexp-legacy)
+
 (defun erc-parse-user (string)
   "Parse STRING as a user specification (nick!login@host).
 
 Return a list of the three separate tokens."
   (cond
-   ((string-match "^\\([^!\n]*\\)!\\([^@\n]*\\)@\\(.*\\)$" string)
+   ((string-match erc--parse-user-regexp string)
     (list (match-string 1 string)
           (match-string 2 string)
           (match-string 3 string)))
diff --git a/test/lisp/erc/erc-tests.el b/test/lisp/erc/erc-tests.el
index 9fdad823059..40334d7d894 100644
--- a/test/lisp/erc/erc-tests.el
+++ b/test/lisp/erc/erc-tests.el
@@ -576,6 +576,39 @@
     (setq erc-lurker-ignore-chars "_-`") ; set of chars, not character alts
     (should (string= "nick" (erc-lurker-maybe-trim "nick-_`")))))
 
+(ert-deftest erc-parse-user ()
+  (should (equal erc--parse-user-regexp erc--parse-user-regexp-legacy))
+
+  (should (equal '("" "" "") (erc-parse-user "!@")))
+  (should (equal '("" "!" "") (erc-parse-user "!!@")))
+  (should (equal '("" "" "@") (erc-parse-user "!@@")))
+  (should (equal '("" "!" "@") (erc-parse-user "!!@@")))
+
+  (should (equal '("abc" "" "") (erc-parse-user "abc")))
+  (should (equal '("" "123" "fake") (erc-parse-user "!123@fake")))
+  (should (equal '("abc" "" "123") (erc-parse-user "abc!123")))
+
+  (should (equal '("abc" "123" "fake") (erc-parse-user "abc!123@fake")))
+  (should (equal '("abc" "!123" "@xy") (erc-parse-user "abc!!123@@xy")))
+
+  (should (equal '("de" "fg" "xy") (erc-parse-user "abc\nde!fg@xy")))
+
+  (ert-info ("`erc--parse-user-regexp-pedantic'")
+    (let ((erc--parse-user-regexp erc--parse-user-regexp-pedantic))
+      (should (equal '("" "" "") (erc-parse-user "!@")))
+      (should (equal '("" "!" "") (erc-parse-user "!!@")))
+      (should (equal '("" "@" "") (erc-parse-user "!@@")))
+      (should (equal '("" "!@" "") (erc-parse-user "!!@@")))
+
+      (should (equal '("abc" "" "") (erc-parse-user "abc")))
+      (should (equal '("" "123" "fake") (erc-parse-user "!123@fake")))
+      (should (equal '("abc" "" "123") (erc-parse-user "abc!123")))
+
+      (should (equal '("abc" "123" "fake") (erc-parse-user "abc!123@fake")))
+      (should (equal '("abc" "!123@" "xy") (erc-parse-user "abc!!123@@xy")))
+
+      (should (equal '("de" "" "fg@xy") (erc-parse-user "abc\nde!fg@xy"))))))
+
 (ert-deftest erc--parse-isupport-value ()
   (should (equal (erc--parse-isupport-value "a,b") '("a" "b")))
   (should (equal (erc--parse-isupport-value "a,b,c") '("a" "b" "c")))