Contribution for #4 breaks existing tests. Slight change to fix this and test S3_USE_CACHE_CONTROL. Finally, it's preferable to take app as argument for functions that are involved in one-time asset upload, so made that modification too.

flask_s3.py

@@ -85,7 +85,8 @@ def _static_folder_path(static_url, static_folder, static_asset):
     # Now bolt the static url path and the relative asset location together
     return u'%s/%s' % (static_url.rstrip('/'), rel_asset.lstrip('/'))
 
-def _write_files(static_url_loc, static_folder, files, bucket, ex_keys=None):
+def _write_files(app, static_url_loc, static_folder, files, bucket, 
+                 ex_keys=None):
     """ Writes all the files inside a static folder to S3. """
     for file_path in files:
         asset_loc = _path_to_relative_url(file_path)
@@ -94,19 +95,16 @@ def _write_files(static_url_loc, static_folder, files, bucket, ex_keys=None):
         if ex_keys and key_name in ex_keys:
             logger.debug("%s excluded from upload" % key_name)
         else:
-            app = current_app
             k = Key(bucket=bucket, name=key_name)
-            if (app.config['S3_USE_CACHE_CONTROL']
-                    and 'S3_CACHE_CONTROL' in app.config):
-                k.metadata.update({
-                    'Cache-Control': app.config['S3_CACHE_CONTROL']
-                })
+            if (app.config['S3_USE_CACHE_CONTROL'] and 
+                'S3_CACHE_CONTROL' in app.config):
+                k.set_metadata('Cache-Control', app.config['S3_CACHE_CONTROL'])
             k.set_contents_from_filename(file_path)
             k.make_public()
 
-def _upload_files(files_, bucket):
+def _upload_files(app, files_, bucket):
     for (static_folder, static_url), names in files_.iteritems():
-        _write_files(static_url, static_folder, names, bucket)
+        _write_files(app, static_url, static_folder, names, bucket)
 
 def create_all(app, user=None, password=None, bucket_name=None, 
                location='', include_hidden=False):
@@ -163,7 +161,7 @@ def create_all(app, user=None, password=None, bucket_name=None,
         bucket.make_public(recursive=True)
     except S3CreateError as e:
         raise e
-    _upload_files(all_files, bucket)
+    _upload_files(app, all_files, bucket)
 
 
 class FlaskS3(object):

tests/test_flask_static.py

@@ -3,6 +3,7 @@ import ntpath
 
 from mock import Mock, patch, call
 from flask import Flask, render_template_string, Blueprint
+from boto.s3.key import Key
 
 import flask_s3
 from flask_s3 import FlaskS3
@@ -28,7 +29,7 @@ class FlaskStaticTest(unittest.TestCase):
         """ Tests configuration vars exist. """
         FlaskS3(self.app)
         defaults = ('S3_USE_HTTPS', 'USE_S3', 'USE_S3_DEBUG', 
-                    'S3_BUCKET_DOMAIN')
+                    'S3_BUCKET_DOMAIN', 'S3_USE_CACHE_CONTROL')
         for default in defaults:
             self.assertIn(default, self.app.config)
 
@@ -107,7 +108,11 @@ class UrlTests(unittest.TestCase):
 class S3Tests(unittest.TestCase):
 
     def setUp(self):
-        self.app = Mock(spec=Flask)
+        self.app = Flask(__name__)
+        self.app.testing = True
+        self.app.config['S3_BUCKET_NAME'] = 'foo'
+        self.app.config['S3_USE_CACHE_CONTROL'] = True
+        self.app.config['S3_CACHE_CONTROL'] = 'cache instruction'
 
     def test__bp_static_url(self):
         """ Tests test__bp_static_url """
@@ -198,10 +203,11 @@ class S3Tests(unittest.TestCase):
         assets = ['/home/z/bar.css', '/home/z/foo.css'] 
         exclude = ['/foo/static/foo.css', '/foo/static/foo/bar.css']
         # we expect foo.css to be excluded and not uploaded
-        expected = [call(bucket=None, name=u'/foo/static/bar.css'), 
+        expected = [call(bucket=None, name=u'/foo/static/bar.css'),
+                    call().set_metadata('Cache-Control', 'cache instruction'), 
                     call().set_contents_from_filename('/home/z/bar.css')]
-        flask_s3._write_files(static_url_loc, static_folder, assets, None, 
-                              exclude)
+        flask_s3._write_files(self.app, static_url_loc, static_folder, assets, 
+                              None, exclude)
         self.assertLessEqual(expected, key_mock.mock_calls)
 
     def test_static_folder_path(self):