Handle multiline error output, as produced by recent sass versions

flymake-sass.el

@@ -11,13 +11,45 @@
 ;;   (add-hook 'sass-mode-hook 'flymake-sass-load)
 (require 'flymake)
 
-(defvar flymake-sass-err-line-patterns '(("^Syntax error on line \\([0-9]+\\): \\(.*\\)$" nil 1 nil 2)))
+
+(defconst flymake-sass-err-line-patterns
+  '(("^Syntax error on line \\([0-9]+\\): \\(.*\\)$" nil 1 nil 2)
+    ("^WARNING on line \\([0-9]+\\) of .*?:\r?\n\\(.*\\)$" nil 1 nil 2)
+    ("^Syntax error: \\(.*\\)\r?\n        on line \\([0-9]+\\) of .*?$" nil 2 nil 1) ;; Older sass versions
+    ))
 
 ;; Invoke utilities with '-c' to get syntax checking
 (defun flymake-sass-init ()
   (list "sass" (list "-c" (flymake-init-create-temp-buffer-copy
                            'flymake-create-temp-inplace))))
 
+;; SASS error output is multiline, and in irregular formats, so we have to hack
+;; flymake-split-output. The hack is activated in `flymake-sass-load', and is
+;; buffer-local
+
+(defun flymake-sass-just-find-all-matches (str &optional ignored)
+  (message "*** patched split")
+  (let ((result nil))
+    (dolist (pattern flymake-sass-err-line-patterns)
+      (let ((regex (car pattern))
+            (pos 0))
+        (while (string-match regex str pos)
+          (push (match-string 0 str) result)
+          (setq pos (match-end 0)))))
+    result))
+
+(defvar flymake-sass--split-multiline nil
+  "Whether flymake's output splitting is to be hacked; do not set this directly.")
+;; Force flymake to find multiline matches
+;; See http://www.emacswiki.org/emacs/flymake-extension.el
+
+(defadvice flymake-split-output
+  (around flymake-sass-split-output-multiline (output) activate protect)
+  (if flymake-sass--split-multiline
+      (flet ((flymake-split-string 'flymake-sass-just-find-all-matches))
+        (setq ad-return-value (list (flymake-sass-just-find-all-matches output) nil)))
+    ad-do-it))
+
 ;;;###autoload
 (defun flymake-sass-load ()
   "Configure flymake mode to check the current buffer's sass syntax.
@@ -28,6 +60,7 @@ alone will not suffice."
   (interactive)
   (set (make-local-variable 'flymake-allowed-file-name-masks) '(("." flymake-sass-init)))
   (set (make-local-variable 'flymake-err-line-patterns) flymake-sass-err-line-patterns)
+  (set (make-local-variable 'flymake-sass--split-multiline) t)
   (if (executable-find "sass")
       (flymake-mode t)
     (message "Not enabling flymake: sass command not found")))