Support filter attribute with empty string

This will enable users to filter list of results with attributes
with empty value. For example, the request below will list
all unbound ports (unbound ports have blank device_id).

  GET "/ports?device_id="

APIImpact
Change-Id: I9001214de126eb888c2425b6a6275f59ec8478e7
Closes-Bug: #1749304

neutron/api/api_common.py

@@ -75,12 +75,14 @@ def get_filters_from_dict(data, attr_info, skips=None):
     becomes:
     {'check': [u'a', u'b'], 'name': [u'Bob']}
     """
+    is_empty_string_supported = is_empty_string_filtering_supported()
     skips = skips or []
     res = {}
     for key, values in data.items():
         if key in skips or hasattr(model_base.BASEV2, key):
             continue
-        values = [v for v in values if v]
+        values = [v for v in values
+                  if v or (v == "" and is_empty_string_supported)]
         key_attr_info = attr_info.get(key, {})
         if 'convert_list_to' in key_attr_info:
             values = key_attr_info['convert_list_to'](values)
@@ -92,6 +94,11 @@ def get_filters_from_dict(data, attr_info, skips=None):
     return res
 
 
+def is_empty_string_filtering_supported():
+    return 'empty-string-filtering' in (extensions.PluginAwareExtensionManager.
+                                        get_instance().extensions)
+
+
 def get_previous_link(request, items, id_key):
     params = request.GET.copy()
     params.pop('marker', None)

neutron/extensions/_empty_string_filtering_lib.py

@@ -0,0 +1,30 @@
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+"""
+TODO(hongbin): This module should be deleted once neutron-lib containing
+https://review.openstack.org/#/c/565342/ change is released.
+"""
+
+
+ALIAS = 'empty-string-filtering'
+IS_SHIM_EXTENSION = True
+IS_STANDARD_ATTR_EXTENSION = False
+NAME = 'Empty String Filtering Extension'
+DESCRIPTION = 'Allow filtering by attributes with empty string value'
+UPDATED_TIMESTAMP = '2018-04-09T10:00:00-00:00'
+RESOURCE_ATTRIBUTE_MAP = {}
+SUB_RESOURCE_ATTRIBUTE_MAP = {}
+ACTION_MAP = {}
+REQUIRED_EXTENSIONS = []
+OPTIONAL_EXTENSIONS = []
+ACTION_STATUS = {}

neutron/extensions/empty_string_filtering.py

@@ -0,0 +1,19 @@
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from neutron_lib.api import extensions
+
+from neutron.extensions import _empty_string_filtering_lib as apidef
+
+
+class Empty_string_filtering(extensions.APIExtensionDescriptor):
+    api_definition = apidef

neutron/plugins/ml2/plugin.py

@@ -158,7 +158,8 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
                                     "default-subnetpools",
                                     "subnet-service-types",
                                     "ip-substring-filtering",
-                                    "port-security-groups-filtering"]
+                                    "port-security-groups-filtering",
+                                    "empty-string-filtering"]
 
     @property
     def supported_extension_aliases(self):

neutron/tests/contrib/hooks/api_all_extensions

@@ -10,6 +10,7 @@ NETWORK_API_EXTENSIONS+=",default-subnetpools"
 NETWORK_API_EXTENSIONS+=",dhcp_agent_scheduler"
 NETWORK_API_EXTENSIONS+=",dns-integration"
 NETWORK_API_EXTENSIONS+=",dvr"
+NETWORK_API_EXTENSIONS+=",empty-string-filtering"
 NETWORK_API_EXTENSIONS+=",ext-gw-mode"
 NETWORK_API_EXTENSIONS+=",external-net"
 NETWORK_API_EXTENSIONS+=",extra_dhcp_opt"

neutron/tests/unit/api/v2/test_base.py

@@ -86,6 +86,7 @@ class APIv2TestBase(base.BaseTestCase):
         self._plugin_patcher = mock.patch(plugin, autospec=True)
         self.plugin = self._plugin_patcher.start()
         instance = self.plugin.return_value
+        instance.supported_extension_aliases = ['empty-string-filtering']
         instance._NeutronPluginBaseV2__native_pagination_support = True
         instance._NeutronPluginBaseV2__native_sorting_support = True
         tools.make_mock_plugin_json_encodable(instance)
@@ -202,7 +203,7 @@ class APIv2TestCase(APIv2TestBase):
         instance.get_networks.return_value = []
 
         self.api.get(_get_path('networks'), {'name': ''})
-        filters = {}
+        filters = {'name': ['']}
         kwargs = self._get_collection_kwargs(filters=filters)
         instance.get_networks.assert_called_once_with(mock.ANY, **kwargs)
 
@@ -211,7 +212,7 @@ class APIv2TestCase(APIv2TestBase):
         instance.get_networks.return_value = []
 
         self.api.get(_get_path('networks'), {'name': ['', '']})
-        filters = {}
+        filters = {'name': ['', '']}
         kwargs = self._get_collection_kwargs(filters=filters)
         instance.get_networks.assert_called_once_with(mock.ANY, **kwargs)
 
@@ -220,7 +221,7 @@ class APIv2TestCase(APIv2TestBase):
         instance.get_networks.return_value = []
 
         self.api.get(_get_path('networks'), {'name': ['bar', '']})
-        filters = {'name': ['bar']}
+        filters = {'name': ['bar', '']}
         kwargs = self._get_collection_kwargs(filters=filters)
         instance.get_networks.assert_called_once_with(mock.ANY, **kwargs)
 
@@ -1552,11 +1553,21 @@ class FiltersTestCase(base.BaseTestCase):
         self.assertEqual({}, api_common.get_filters(request, None,
                                                     ["fields"]))
 
-    def test_blank_values(self):
+    @mock.patch('neutron.api.api_common.is_empty_string_filtering_supported',
+                return_value=False)
+    def test_blank_values(self, mock_is_supported):
         path = '/?foo=&bar=&baz=&qux='
         request = webob.Request.blank(path)
         self.assertEqual({}, api_common.get_filters(request, {}))
 
+    @mock.patch('neutron.api.api_common.is_empty_string_filtering_supported',
+                return_value=True)
+    def test_blank_values_with_filtering_supported(self, mock_is_supported):
+        path = '/?foo=&bar=&baz=&qux='
+        request = webob.Request.blank(path)
+        self.assertEqual({'foo': [''], 'bar': [''], 'baz': [''], 'qux': ['']},
+                         api_common.get_filters(request, {}))
+
     def test_no_attr_info(self):
         path = '/?foo=4&bar=3&baz=2&qux=1'
         request = webob.Request.blank(path)

releasenotes/notes/support-empty-string-filtering-4a39096b62b9abf2.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Add support for filtering attributes with value as empty string. A shim
+    extension is added to indicate if this feature is supported.