Enhance GET /v3 to handle Accept header

Keystone wasn't handling the Accept header for GET /v3 according to
the HTTP 1.1 spec[1]. This change enhances the Keystone server so
that it supports using multiple values and qvalues in the Accept
header for GET /v3. This allows requesting a JSON Home or JSON
response with a preference for JSON Home, for example.

[1] http://tools.ietf.org/html/rfc2616#section-14.1

bp json-home

Change-Id: Ifb204b6860c61a874ecbf92388878685ac437987

keystone/common/wsgi.py

@@ -193,6 +193,7 @@ class Application(BaseApplication):
         # values by the container and processed by the pipeline.  the complete
         # set is not yet know.
         context['environment'] = req.environ
+        context['accept_header'] = req.accept
         req.environ = None
 
         params.update(arg_dict)

keystone/controllers.py

@@ -60,6 +60,23 @@ def register_version(version):
     _VERSIONS.append(version)
 
 
+class MimeTypes:
+    JSON = 'application/json'
+    JSON_HOME = 'application/json-home'
+
+
+def v3_mime_type_best_match(context):
+
+    # accept_header is a WebOb MIMEAccept object so supports best_match.
+    accept_header = context['accept_header']
+
+    if not accept_header:
+        return MimeTypes.JSON
+
+    SUPPORTED_TYPES = [MimeTypes.JSON, MimeTypes.JSON_HOME]
+    return accept_header.best_match(SUPPORTED_TYPES)
+
+
 class Version(wsgi.Application):
 
     def __init__(self, version_type, routers=None):
@@ -157,10 +174,12 @@ class Version(wsgi.Application):
     def get_version_v3(self, context):
         versions = self._get_versions_list(context)
         if 'v3' in _VERSIONS:
-            if context['headers'].get('Accept') == 'application/json-home':
+            req_mime_type = v3_mime_type_best_match(context)
+
+            if req_mime_type == MimeTypes.JSON_HOME:
                 return wsgi.render_response(
                     body=self._get_json_home_v3(),
-                    headers=(('Content-Type', 'application/json-home'),))
+                    headers=(('Content-Type', MimeTypes.JSON_HOME),))
 
             return wsgi.render_response(body={
                 'version': versions['v3']

keystone/tests/test_versions.py

@@ -563,6 +563,48 @@ class VersionTestCase(tests.TestCase):
         self.assertThat(jsonutils.loads(resp.body),
                         tt_matchers.Equals(exp_json_home_data))
 
+    def test_accept_type_handling(self):
+        # Accept headers with multiple types and qvalues are handled.
+
+        def make_request(accept_types=None):
+            client = self.client(self.public_app)
+            headers = None
+            if accept_types:
+                headers = {'Accept': accept_types}
+            resp = client.get('/v3', headers=headers)
+            self.assertThat(resp.status, tt_matchers.Equals('200 OK'))
+            return resp.headers['Content-Type']
+
+        JSON = controllers.MimeTypes.JSON
+        JSON_HOME = controllers.MimeTypes.JSON_HOME
+
+        JSON_MATCHER = tt_matchers.Equals(JSON)
+        JSON_HOME_MATCHER = tt_matchers.Equals(JSON_HOME)
+
+        # Default is JSON.
+        self.assertThat(make_request(), JSON_MATCHER)
+
+        # Can request JSON and get JSON.
+        self.assertThat(make_request(JSON), JSON_MATCHER)
+
+        # Can request JSONHome and get JSONHome.
+        self.assertThat(make_request(JSON_HOME), JSON_HOME_MATCHER)
+
+        # If request JSON, JSON Home get JSON.
+        accept_types = '%s, %s' % (JSON, JSON_HOME)
+        self.assertThat(make_request(accept_types), JSON_MATCHER)
+
+        # If request JSON Home, JSON get JSON.
+        accept_types = '%s, %s' % (JSON_HOME, JSON)
+        self.assertThat(make_request(accept_types), JSON_MATCHER)
+
+        # If request JSON Home, JSON;q=0.5 get JSON Home.
+        accept_types = '%s, %s;q=0.5' % (JSON_HOME, JSON)
+        self.assertThat(make_request(accept_types), JSON_HOME_MATCHER)
+
+        # If request some unknown mime-type, get JSON.
+        self.assertThat(make_request(self.getUniqueString()), JSON_MATCHER)
+
 
 class VersionInheritEnabledTestCase(tests.TestCase):
     def setUp(self):