service: fix navigation in EntityProxy

Author: Masterchen09

pyodata/v2/service.py

@@ -878,14 +878,40 @@ def nav(self, nav_property):
         navigation_entity_set = self._service.schema.entity_set(end.entity_set_name)
 
         if navigation_property.to_role.multiplicity != model.EndRole.MULTIPLICITY_ZERO_OR_MORE:
-            return NavEntityProxy(self, nav_property, navigation_entity_set.entity_type, {})
+            return self._get_nav_entity(nav_property, navigation_entity_set)
 
         return EntitySetProxy(
             self._service,
             self._service.schema.entity_set(navigation_entity_set.name),
             nav_property,
             self._entity_set.name + self._entity_key.to_key_string())
 
+    def _get_nav_entity(self, nav_property, navigation_entity_set):
+        """Get entity based on Navigation property name"""
+
+        def get_entity_handler(parent, nav_property, navigation_entity_set, response):
+            """Gets entity from HTTP response"""
+
+            if response.status_code != HTTP_CODE_OK:
+                raise HttpError('HTTP GET for Entity {0} failed with status code {1}'
+                                .format(self._name, response.status_code), response)
+
+            entity = response.json()['d']
+
+            return NavEntityProxy(parent, nav_property, navigation_entity_set.entity_type, entity)
+
+        self._logger.info(
+            'Getting the nav property %s of the entity %s for the key %s',
+            nav_property,
+            self._entity_set,
+            self.entity_key)
+
+        return NavEntityGetRequest(
+            partial(get_entity_handler, self, nav_property, navigation_entity_set),
+            self.entity_key,
+            getattr(self._service.entity_sets, self.entity_set.name),
+            nav_property)
+
     def get_path(self):
         """Returns this entity's relative path - e.g. EntitySet(KEY)"""
 

tests/test_service_v2.py

@@ -1103,6 +1103,51 @@ def test_navigation_1on1(service):
     assert idpic_proxy.Content == 'DEADBEAF'
 
 
+@responses.activate
+def test_navigation_1on1_from_entity_proxy(service):
+    """Check getting entity via navigation property"""
+
+    # pylint: disable=redefined-outer-name
+
+    responses.add(
+        responses.GET,
+        f"{service.url}/Cars('Hadraplan')",
+        headers={'Content-type': 'application/json'},
+        json = { 'd': {
+            'Name': 'Hadraplan',
+            }
+        },
+        status=200)
+
+    responses.add(
+        responses.GET,
+        f"{service.url}/Cars('Hadraplan')/IDPic",
+        headers={'Content-type': 'application/json'},
+        json = { 'd': {
+            'CarName': 'Hadraplan',
+            'Content': 'DEADBEAF',
+            }
+        },
+        status=200)
+
+    request = service.entity_sets.Cars.get_entity('Hadraplan')
+    assert isinstance(request, pyodata.v2.service.EntityGetRequest)
+
+    car_proxy = request.execute()
+    assert isinstance(car_proxy, pyodata.v2.service.EntityProxy)
+
+    assert car_proxy.Name == 'Hadraplan'
+
+    idpic_proxy = car_proxy.nav('IDPic').execute()
+    assert isinstance(idpic_proxy, pyodata.v2.service.NavEntityProxy)
+
+    assert idpic_proxy.entity_set._name == 'Cars'
+    assert idpic_proxy._entity_type.name == 'CarIDPic'
+
+    assert idpic_proxy.CarName == 'Hadraplan'
+    assert idpic_proxy.Content == 'DEADBEAF'
+
+
 @responses.activate
 def test_navigation_1on1_get_value_without_proxy(service):
     """Check getting $value via navigation property"""