Handle vendor prefixed expressions

Author: sevastos

lib/calc.js

@@ -36,8 +36,10 @@ module.exports = function (style) {
  * Constants
  */
 var DEFAULT_UNIT = 'px',
-    EXPRESSION_METHOD_NAME = 'calc',
-    EXPRESSION_REGEXP = '\\b' + EXPRESSION_METHOD_NAME + '\\(';
+    EXPRESSION_METHOD_NAME =  'calc',
+    EXPRESSION_OPT_VENDOR_PREFIX = '(\\-[a-z]+\\-)?',
+    EXPRESSION_METHOD_REGEXP = EXPRESSION_OPT_VENDOR_PREFIX + EXPRESSION_METHOD_NAME,
+    EXPRESSION_REGEXP = '\\b' + EXPRESSION_METHOD_REGEXP + '\\(';
 
 /**
  * Visit all rules
@@ -123,7 +125,11 @@ function evaluateAndApplyExpressions(expressions, declaration) {
         if (!result) return;
 
         // Insert the evaluated value:
-        declaration.value = declaration.value.replace(EXPRESSION_METHOD_NAME + '(' + expression + ')', result);
+        var expRegexp = new RegExp(
+                                EXPRESSION_METHOD_REGEXP + '\\(' +
+                                escapeExp(expression) + '\\)'
+                            );
+        declaration.value = declaration.value.replace(expRegexp, result);
     });
 }
 
@@ -201,3 +207,14 @@ function getUnitsInExpression(expression) {
 
     return uniqueUnits;
 }
+
+/**
+ * Escape string for inclusion in a regex pattern without conflicts
+ *
+ * @param  {String} str String to escape
+ * @return {String} Escaped string
+ * @api private
+ */
+function escapeExp(str) {
+    return String(str).replace(/([.*+?^=!:${}()|\[\]\/\\])/g, '\\$1');
+}