Merge pull request #1318 from xzyfer/fix/importer-async-null

Handle sass.NULL returned from the importer via done()

lib/index.js

@@ -301,27 +301,27 @@ module.exports.render = function(options, cb) {
     if (Array.isArray(importer)) {
       importer.forEach(function(subject, index) {
         options.importer[index] = function(file, prev, bridge) {
-          function done(data) {
-            bridge.success(data);
+          function done(result) {
+            bridge.success(result === module.exports.NULL ? null : result);
           }
 
           var result = subject.call(options.context, file, prev, done);
 
-          if (result) {
-            done(result === module.exports.NULL ? null : result);
+          if (result !== undefined) {
+            done(result);
           }
         };
       });
     } else {
       options.importer = function(file, prev, bridge) {
-        function done(data) {
-          bridge.success(data);
+        function done(result) {
+          bridge.success(result === module.exports.NULL ? null : result);
         }
 
         var result = importer.call(options.context, file, prev, done);
 
-        if (result) {
-          done(result === module.exports.NULL ? null : result);
+        if (result !== undefined) {
+          done(result);
         }
       };
     }

test/api.js

@@ -325,6 +325,17 @@ describe('api', function() {
       });
     });
 
+    it('should fallback to default import behaviour if importer returns sass.NULL', function(done) {
+      sass.render({
+        file: fixture('include-files/index.scss'),
+        importer: function(url, prev, done) {
+          done(sass.NULL);
+        }
+      }, function(error, result) {
+        assert.equal(result.css.toString().trim(), '/* foo.scss */\n/* bar.scss */');
+        done();
+      });
+    });
 
     it('should fallback to default import behaviour if importer returns null for backwards compatibility', function(done) {
       sass.render({