Fix up some Content-Type handling in account/container listings

Update content type on 204 (not just 200) to properly handle HEAD
requests from xml/txt listings.

Add "Vary: Accept" header to listings, since otherwise, browsers may
serve the wrong content type from cache (even though we *would have*
sent the *right* type if it actually sent the request).

Change-Id: Iaa333aaca36a8dc2df65d38ef2173e3a6e2000ee

swift/common/middleware/listing_formats.py

@@ -22,7 +22,7 @@ from swift.common.http import HTTP_NO_CONTENT
 from swift.common.request_helpers import get_param
 from swift.common.swob import HTTPException, HTTPNotAcceptable, Request, \
     RESPONSE_REASONS, HTTPBadRequest, wsgi_quote, wsgi_to_bytes
-from swift.common.utils import RESERVED, get_logger
+from swift.common.utils import RESERVED, get_logger, list_from_csv
 
 
 #: Mapping of query string ``format=`` values to their corresponding
@@ -167,6 +167,7 @@ class ListingFilter(object):
             return err(env, start_response)
 
         params = req.params
+        can_vary = 'format' not in params
         params['format'] = 'json'
         req.params = params
 
@@ -187,11 +188,22 @@ class ListingFilter(object):
             elif header == 'content-length':
                 header_to_index[header] = i
                 resp_length = int(value)
+            elif header == 'vary':
+                header_to_index[header] = i
 
-        if not status.startswith('200 '):
+        if not status.startswith(('200 ', '204 ')):
             start_response(status, headers)
             return resp_iter
 
+        if can_vary:
+            if 'vary' in header_to_index:
+                value = headers[header_to_index['vary']][1]
+                if 'accept' not in list_from_csv(value.lower()):
+                    headers[header_to_index['vary']] = (
+                        'Vary', value + ', Accept')
+            else:
+                headers.append(('Vary', 'Accept'))
+
         if resp_content_type != 'application/json':
             start_response(status, headers)
             return resp_iter

test/unit/common/middleware/test_listing_formats.py

@@ -16,7 +16,7 @@
 import json
 import unittest
 
-from swift.common.swob import Request, HTTPOk
+from swift.common.swob import Request, HTTPOk, HTTPNoContent
 from swift.common.middleware import listing_formats
 from swift.common.request_helpers import get_reserved_name
 from test.unit import debug_logger
@@ -106,6 +106,64 @@ class TestListingFormats(unittest.TestCase):
         self.assertEqual(self.fake_swift.calls[-1], (
             'GET', '/v1/a?format=json'))
 
+    def test_valid_content_type_on_txt_head(self):
+        self.fake_swift.register('HEAD', '/v1/a', HTTPNoContent, {
+            'Content-Length': str(len(self.fake_account_listing)),
+            'Content-Type': 'application/json'}, self.fake_account_listing)
+        req = Request.blank('/v1/a', method='HEAD')
+        resp = req.get_response(self.app)
+        self.assertEqual(resp.body, b'')
+        self.assertEqual(resp.headers['Content-Type'],
+                         'text/plain; charset=utf-8')
+        self.assertIn('Vary', resp.headers)
+        # Even though the client didn't send an Accept header, the response
+        # could change *if a subsequent request does*, so include Vary: Accept
+        self.assertEqual(resp.headers['Vary'], 'Accept')
+        self.assertEqual(self.fake_swift.calls[-1], (
+            'HEAD', '/v1/a?format=json'))
+
+    def test_valid_content_type_on_xml_head(self):
+        self.fake_swift.register('HEAD', '/v1/a', HTTPNoContent, {
+            'Content-Length': str(len(self.fake_account_listing)),
+            'Content-Type': 'application/json'}, self.fake_account_listing)
+        req = Request.blank('/v1/a?format=xml', method='HEAD')
+        resp = req.get_response(self.app)
+        self.assertEqual(resp.body, b'')
+        self.assertEqual(resp.headers['Content-Type'],
+                         'application/xml; charset=utf-8')
+        # query param overrides header, so it won't vary
+        self.assertNotIn('Vary', resp.headers)
+        self.assertEqual(self.fake_swift.calls[-1], (
+            'HEAD', '/v1/a?format=json'))
+
+    def test_update_vary_if_present(self):
+        self.fake_swift.register('HEAD', '/v1/a', HTTPNoContent, {
+            'Content-Length': str(len(self.fake_account_listing)),
+            'Content-Type': 'application/json',
+            'Vary': 'Origin'}, self.fake_account_listing)
+        req = Request.blank('/v1/a', method='HEAD')
+        resp = req.get_response(self.app)
+        self.assertEqual(resp.body, b'')
+        self.assertEqual(resp.headers['Content-Type'],
+                         'text/plain; charset=utf-8')
+        self.assertEqual(resp.headers['Vary'], 'Origin, Accept')
+        self.assertEqual(self.fake_swift.calls[-1], (
+            'HEAD', '/v1/a?format=json'))
+
+    def test_update_vary_does_not_duplicate(self):
+        self.fake_swift.register('HEAD', '/v1/a', HTTPNoContent, {
+            'Content-Length': str(len(self.fake_account_listing)),
+            'Content-Type': 'application/json',
+            'Vary': 'Accept'}, self.fake_account_listing)
+        req = Request.blank('/v1/a', method='HEAD')
+        resp = req.get_response(self.app)
+        self.assertEqual(resp.body, b'')
+        self.assertEqual(resp.headers['Content-Type'],
+                         'text/plain; charset=utf-8')
+        self.assertEqual(resp.headers['Vary'], 'Accept')
+        self.assertEqual(self.fake_swift.calls[-1], (
+            'HEAD', '/v1/a?format=json'))
+
     def test_valid_account_with_reserved(self):
         body_len = len(self.fake_account_listing_with_reserved)
         self.fake_swift.register(