[FEATURE] Override sourceMappingURL with custom function (Closes #24)

README.md

@@ -73,6 +73,10 @@ CSS compression function or predefined `mincer` css compressor identifier `"csso
 
 The base url to use when referencing source-maps in compiled assets. Defaults to `""` if not explicitly set.
 
+#### sourceMappingURL ```function(options, file)```
+
+Optional function that is called to determine the sourceMappingURL for a file. Has access to the grunt task options as well as the file object for current asset. By default returns the destination filename prefixed with the `sourceMappingBaseURL`
+
 ### Files
 
 The files on which the task operates can be defined using all the powerful options provided by Grunt.

tasks/lib/helpers.js

@@ -177,10 +177,11 @@ exports.init = function (grunt) {
       });
 
       if([].concat(options.enable).indexOf('source_maps') > -1) {
+        var mapUrl = options.sourceMappingURL(options, file);
         if (/\.css$/.test(file.dest)) {
-          sourceNode.add('/*# sourceMappingURL=' + options.sourceMappingBaseURL + file.dest + '.map' + ' */');
+          sourceNode.add('/*# sourceMappingURL=' + mapUrl + ' */');
         } else {
-          sourceNode.add('//# sourceMappingURL=' + options.sourceMappingBaseURL + file.dest + '.map');
+          sourceNode.add('//# sourceMappingURL=' + mapUrl);
         }
       }
 

tasks/mincer.js

@@ -23,6 +23,7 @@ module.exports = function (grunt) {
         embedMappingComments: true
       },
       sourceMappingBaseURL: '',
+      sourceMappingURL: function (options, file) { return options.sourceMappingBaseURL + file.dest + '.map' },
       helpers: {},
       engines: {},
       jsCompressor: null,