From b75ba0efbb44bda6a6da04d38490456a2545aa99 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <jp@neverwas.me>
Date: Mon, 17 Apr 2023 23:09:49 -0700
Subject: [PATCH 1/3] [5.6] Don't send multiline slash commands as msgs in ERC

* lisp/erc/erc.el (erc-command-regexp): Relocate from further down in
same file.
(erc--check-prompt-input-for-multiline-command: Reject slash commands
containing multiple lines during input validation and before running
additional hooks.
(erc--discard-trailing-multiline-nulls): Don't mark
input that begins with a possible "slash command" as constituting a
plain message just because it has a trailing newline.  It's relatively
easy to add a newline by accident, which can result in the unintended
sharing of a command line.  ERC already has a /SAY command that allows
a user to send a message starting a literal command.
* test/lisp/erc/erc-tests.el (erc-send-whitespace-lines): Fix test to
expect validation error when non-blank lines follow a slash command.
(Bug#62947)
---
 lisp/erc/erc.el            | 23 +++++++++++++++--------
 test/lisp/erc/erc-tests.el | 16 ++++++++++++----
 2 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 284990e2d43..09e65671545 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -6005,6 +6005,9 @@ erc-accidental-paste-threshold-seconds
 
 (defvar erc--input-line-delim-regexp (rx (| (: (? ?\r) ?\n) ?\r)))
 
+(defvar erc-command-regexp "^/\\([A-Za-z']+\\)\\(\\s-+.*\\|\\s-*\\)$"
+  "Regular expression used for matching commands in ERC.")
+
 (defun erc--blank-in-multiline-input-p (lines)
   "Detect whether LINES contains a blank line.
 When `erc-send-whitespace-lines' is in effect, return nil if
@@ -6054,11 +6057,19 @@ erc--check-prompt-input-for-running-process
               (erc-command-no-process-p string))
     "ERC: No process running"))
 
+(defun erc--check-prompt-input-for-multiline-command (line lines)
+  "Return non-nil when non-blank lines follow a command line."
+  (when (and (cdr lines)
+             (string-match erc-command-regexp line)
+             (seq-drop-while #'string-empty-p (reverse (cdr lines))))
+    "Excess input after command line"))
+
 (defvar erc--check-prompt-input-functions
   '(erc--check-prompt-input-for-point-in-bounds
     erc--check-prompt-input-for-multiline-blanks
     erc--check-prompt-input-for-running-process
-    erc--check-prompt-input-for-excess-lines)
+    erc--check-prompt-input-for-excess-lines
+    erc--check-prompt-input-for-multiline-command)
   "Validators for user input typed at prompt.
 Called with latest input string submitted by user and the list of
 lines produced by splitting it.  If any member function returns
@@ -6113,19 +6124,15 @@ erc-user-input
    erc-input-marker
    (erc-end-of-input-line)))
 
-(defvar erc-command-regexp "^/\\([A-Za-z']+\\)\\(\\s-+.*\\|\\s-*\\)$"
-  "Regular expression used for matching commands in ERC.")
-
 (defun erc--discard-trailing-multiline-nulls (state)
   "Ensure last line of STATE's string is non-null.
 But only when `erc-send-whitespace-lines' is non-nil.  STATE is
 an `erc--input-split' object."
   (when (and erc-send-whitespace-lines (erc--input-split-lines state))
     (let ((reversed (nreverse (erc--input-split-lines state))))
-      (when (string-empty-p (car reversed))
-        (pop reversed)
-        (setf (erc--input-split-cmdp state) nil))
-      (nreverse (seq-drop-while #'string-empty-p reversed)))))
+      (while (and reversed (string-empty-p (car reversed)))
+        (setq reversed (cdr reversed)))
+      (setf (erc--input-split-lines state) (nreverse reversed)))))
 
 (defun erc-send-input (input &optional skip-ws-chk)
   "Treat INPUT as typed in by the user.
diff --git a/test/lisp/erc/erc-tests.el b/test/lisp/erc/erc-tests.el
index 29bda7e742d..574df4106ee 100644
--- a/test/lisp/erc/erc-tests.el
+++ b/test/lisp/erc/erc-tests.el
@@ -1236,15 +1236,23 @@ erc-send-whitespace-lines
        (pcase-dolist (`(,p . ,q)
                       '(("/a b\r" "/a b\n") ("/a b\n" "/a b\n")
                         ("/a b\n\n" "/a b\n") ("/a b\r\n" "/a b\n")
-                        ("a b\nc\n\n" "c\n" "a b\n")
-                        ("/a b\nc\n\n" "c\n" "/a b\n")
-                        ("/a b\n\nc\n\n" "c\n" "\n" "/a b\n")))
+                        ("/a b\n\n\n" "/a b\n")))
          (insert p)
          (erc-send-current-line)
          (erc-bol)
          (should (eq (point) (point-max)))
          (while q
-           (should (equal (funcall next) (list (pop q) nil t))))
+           (should (pcase (funcall next)
+                     (`(,cmd ,_ nil) (equal cmd (pop q))))))
+         (should-not (funcall next))))
+
+     (ert-info ("Multiline command with non-blanks errors")
+       (dolist (p '("/a b\nc\n\n" "/a b\n/c\n\n" "/a b\n\nc\n\n"
+                    "/a\n c\n" "/a\nb\n" "/a\n/b\n" "/a \n \n"))
+         (insert p)
+         (should-error (erc-send-current-line))
+         (goto-char erc-input-marker)
+         (delete-region (point) (point-max))
          (should-not (funcall next))))
 
      (ert-info ("Multiline hunk with trailing whitespace not filtered")
-- 
2.40.0