A fix for #2. Slightly different approach to @rdegges as static_folder is the main issue. Plus some tests.

flask_s3.py

@@ -42,14 +42,15 @@ def url_for(endpoint, **values):
 
 def _bp_static_url(blueprint):
     """ builds the absolute url path for a blueprint's static folder """
-    return u'%s%s' % (blueprint.url_prefix or '', blueprint.static_url_path)
+    return u'%s%s' % (blueprint.url_prefix or '', blueprint.static_url_path or '')
 
 def _gather_files(app, hidden):
     """ Gets all files in static folders and returns in dict."""
     dirs = [(unicode(app.static_folder), app.static_url_path)]
     if hasattr(app, 'blueprints'):
+        blueprints = app.blueprints.values()
         bp_details = lambda x: (x.static_folder, _bp_static_url(x))
-        dirs.extend([bp_details(x) for x in app.blueprints.values()])
+        dirs.extend([bp_details(x) for x in blueprints if x.static_folder])
         
     valid_files = defaultdict(list)
     for static_folder, static_url_loc  in dirs:

tests/test_flask_static.py

@@ -109,15 +109,15 @@ class S3Tests(unittest.TestCase):
     def setUp(self):
         self.app = Mock(spec=Flask)
 
-
     def test__bp_static_url(self):
         """ Tests test__bp_static_url """
         bps = [Mock(static_url_path='/foo', url_prefix=None), 
-               Mock(static_url_path='/b/bar', url_prefix='/pref')]
-        expected = [u'/foo', u'/pref/b/bar']
+               Mock(static_url_path=None, url_prefix='/pref'),
+               Mock(static_url_path='/b/bar', url_prefix='/pref'),
+               Mock(static_url_path=None, url_prefix=None)]
+        expected = [u'/foo', u'/pref', u'/pref/b/bar', u'']
         self.assertEquals(expected, [flask_s3._bp_static_url(x) for x in bps])
 
-
     @patch('os.walk')
     @patch('os.path.isdir')
     def test__gather_files(self, path_mock, os_mock):
@@ -129,7 +129,9 @@ class S3Tests(unittest.TestCase):
                     url_prefix=None)
         bp_b = Mock(static_folder='/home/zoo', static_url_path='/b/bar', 
                     url_prefix=None)
-        self.app.blueprints = { 'a': bp_a, 'b': bp_b}
+        bp_c = Mock(static_folder=None)
+
+        self.app.blueprints = { 'a': bp_a, 'b': bp_b, 'c': bp_c}
         dirs = { '/home': [('/home', None, ['.a'])],
                  '/home/bar': [('/home/bar', None, ['b'])],
                  '/home/zoo': [('/home/zoo', None, ['c']),