lava-mode: handle the embedded elisp a little better

This involves doing a custom font-lock pass to ensure we don't break the
syntax table.

1 files changed, 37 insertions, 4 deletions

diff --git a/lava-mode.el b/lava-mode.el
index 670362d..e72c231 100644
--- a/lava-mode.el
+++ b/lava-mode.el
@@ -39,8 +39,8 @@
 
 ;; Font lock related stuff
 (defvar lava-keywords
-  '("job_name" "device_type" "timeout" "actions" "command"
-    "parameters" "image" "testdef_urls")
+  '("\"job_name\"" "\"device_type\"" "\"timeout\"" "\"actions\"" "\"command\""
+    "\"parameters\"" "\"image\"" "\"priority\"" "\"testdef_urls\"")
   "LAVA specific keywords.")
 
 (defvar lava-mode-elisp-escape-regex
@@ -55,6 +55,16 @@
    )
   "LAVA specific font-lock definitions, used ontop of parent mode.")
 
+(defvar lava-mode-syntax-table
+  (let ((json-table (copy-syntax-table json-mode-syntax-table)))
+    (modify-syntax-entry ?` "|" json-table)
+    json-table)
+  "LAVA Mode syntax table.
+This is tweaked version of json-mode-syntax-table with the escape
+character treated as a string escape.  The
+`lava-mode-set-syntax-then-fontify' function will ensure the elisp
+bits are correctly tagged.")
+
 (defvar lava-mode-device-list
   nil
   "List of all device types on we could handle.")
@@ -85,6 +95,26 @@
     map)
   "Keymap for major mode `lava-mode'.")
 
+;; Font locking magic
+;; See: http://emacs.stackexchange.com/questions/3349/how-can-i-nest-one-syntax-table-in-another
+;;
+(defun lava-mode-set-syntax-then-fontify (beg end loudly)
+  "Apply elisp syntax table to relevant regions before calling font-lock."
+  (save-match-data
+    (save-excursion
+      (save-restriction
+        (widen)
+        (narrow-to-region beg end)
+        (while (search-forward "`" nil 'noerror)
+          ;; Using `end' here excludes the `, I don't which syntax you
+          ;; want to apply to that.
+          (let ((left (match-end 0)))
+            (when (search-forward "`" nil 'noerror)
+              (add-text-properties
+               left (match-beginning 0)
+               (list 'syntax-table emacs-lisp-mode-syntax-table))))))))
+  (font-lock-default-fontify-region beg end loudly))
+
 ;; Define the mode
 
 ;;###autoload
@@ -93,8 +123,11 @@
 
 \\{lava-mode-map}"
   :lighter " LAVA"
-  (setq-local font-lock-defaults '((lava-font-lock-defaults)
-                                   (json-font-lock-keywords-1 t))))
+  (progn
+    (setq-local font-lock-defaults '((lava-font-lock-defaults)
+                                     (json-font-lock-keywords-1 t)))
+    (set (make-local-variable 'font-lock-fontify-region-function)
+         #'lava-mode-set-syntax-then-fontify)))
 
 (defun lava-mode-submit-job (arg)
   "Submit a the current buffer JSON job to LAVA.