grunt-newer configuration to only preprocess scss files that have imported files that have changed

checkFileForModifiedImports

# grunt-newer: 
# Check for newer @import .scss files example
# See: https://github.com/tschaub/grunt-newer/issues/29

newer: {
    options: {
      override: function(details, include) {
        if (details.task === 'sass') {
          checkForNewerImports(details.path, details.time, include);
        }
        else {
          include(false);
        }

        function checkForNewerImports(scssFile, mTime, include) {
          fs.readFile(scssFile, "utf8", function(err, data) {
              var scssDir = path.dirname(scssFile),
                  regex = /\@import \"(.+?)(\.scss)?\"\;/g,
                  shouldInclude = false,
                  match;

              while ((match = regex.exec(data)) !== null) {
                  // i.e. @import "modules/header/file";
                  var scssDirPath = match[1].substr(0, match[1].lastIndexOf('/')); // modules/header
                  var scssPartial = match[1].substr(match[1].lastIndexOf('/')+1);  // file
                  // because scss files are formatted as _partial.scss we have to parse and add it in
                  var importFile = scssDir + '/' + scssDirPath + '/_' + scssPartial + '.scss';
                  if (fs.existsSync(importFile)) {
                      var stat = fs.statSync(importFile);
                      if (stat.mtime > mTime) {
                          shouldInclude = true;
                          break;
                      }
                  }
              }
              include(shouldInclude);
          });
        }
      }
    }
  }