Summary: Improve sexp-based movement in message-mode

Works by giving citations and smileys a different syntax.  This helps
modes like `show-paren-mode', `electric-pair-mode', and C-M-*
sexp-based movement.

* lisp/gnus/message.el (message--syntax-propertize): New function.
(message-mode): Set syntax-related vars.
(message-smileys): New variable.

* test/automated/message-mode-tests.el: New file

1 files changed, 31 insertions, 1 deletions

diff --git a/lisp/gnus/message.el b/lisp/gnus/message.el
index 04145ded107..b1bee65b7fe 100644
--- a/lisp/gnus/message.el
+++ b/lisp/gnus/message.el
@@ -2961,6 +2961,30 @@ See also `message-forbidden-properties'."
 
 (autoload 'ecomplete-setup "ecomplete") ;; for Emacs <23.
 
+(defvar message-smileys '(":-)" ":)"
+                          ":-(" ":("
+                          ";-)" ";)")
+  "A list of recognized smiley faces in `message-mode'.")
+
+(defun message--syntax-propertize (beg end)
+  "Syntax-propertize certain message text specially."
+  (let ((citation-regexp (concat "^" message-cite-prefix-regexp ".*$"))
+        (smiley-regexp (regexp-opt message-smileys)))
+    (goto-char beg)
+    (while (search-forward-regexp citation-regexp
+                                  end 'noerror)
+      (let ((start (match-beginning 0))
+            (end (match-end 0)))
+        (add-text-properties start (1+ start)
+                             `(syntax-table ,(string-to-syntax "<")))
+        (add-text-properties end (min (1+ end) (point-max))
+                             `(syntax-table ,(string-to-syntax ">")))))
+    (goto-char beg)
+    (while (search-forward-regexp smiley-regexp
+            end 'noerror)
+      (add-text-properties (match-beginning 0) (match-end 0)
+                           `(syntax-table ,(string-to-syntax "."))))))
+
 ;;;###autoload
 (define-derived-mode message-mode text-mode "Message"
   "Major mode for editing mail and news to be sent.
@@ -3063,7 +3087,13 @@ M-RET    `message-newline-and-reformat' (break the line and reformat)."
     ;; multibyte is not necessary at all. -- zsh
     (mm-enable-multibyte))
   (set (make-local-variable 'indent-tabs-mode) nil) ;No tabs for indentation.
-  (mml-mode))
+  (mml-mode)
+  ;; Syntactic fontification. Helps `show-paren-mode',
+  ;; `electric-pair-mode', and C-M-* navigation by syntactically
+  ;; excluding citations and other artifacts.
+  ;;
+  (setq-local syntax-propertize-function 'message--syntax-propertize)
+  (setq-local parse-sexp-ignore-comments t))
 
 (defun message-setup-fill-variables ()
   "Setup message fill variables."