Add a starter class for _gax.

vision/google/cloud/vision/_gax.py

@@ -0,0 +1,25 @@
+# Copyright 2016 Google Inc.
+#
+# 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.
+
+"""GAX Client for interacting with the Google Cloud Vision API."""
+
+
+class _GAPICVisionAPI(object):
+    """Vision API for interacting with the gRPC version of Vision.
+
+    :type client: :class:`~google.cloud.core.client.Client`
+    :param client: Instance of ``Client`` object.
+    """
+    def __init__(self, client=None):
+        raise NotImplementedError

vision/google/cloud/vision/client.py

@@ -14,12 +14,20 @@
 
 """Client for interacting with the Google Cloud Vision API."""
 
+import os
+
 from google.cloud.client import JSONClient
+from google.cloud.environment_vars import DISABLE_GRPC
+
+from google.cloud.vision._gax import _GAPICVisionAPI
 from google.cloud.vision.connection import Connection
 from google.cloud.vision.image import Image
 from google.cloud.vision._http import _HTTPVisionAPI
 
 
+_USE_GAX = not os.getenv(DISABLE_GRPC, False)
+
+
 class Client(JSONClient):
     """Client to bundle configuration needed for API requests.
 
@@ -40,14 +48,25 @@ class Client(JSONClient):
                  :meth:`~httplib2.Http.request`. If not passed, an
                  ``http`` object is created that is bound to the
                  ``credentials`` for the current object.
+
+    :type use_gax: bool
+    :param use_gax: (Optional) Explicitly specifies whether
+                    to use the gRPC transport (via GAX) or HTTP. If unset,
+                    falls back to the ``GOOGLE_CLOUD_DISABLE_GRPC`` environment
+                    variable
     """
     _vision_api_internal = None
 
-    def __init__(self, project=None, credentials=None, http=None):
+    def __init__(self, project=None, credentials=None, http=None,
+                 use_gax=False):
         super(Client, self).__init__(
             project=project, credentials=credentials, http=http)
         self._connection = Connection(
             credentials=self._credentials, http=self._http)
+        if use_gax is None:
+            self._use_gax = _USE_GAX
+        else:
+            self._use_gax = use_gax
 
     def image(self, content=None, filename=None, source_uri=None):
         """Get instance of Image using current client.
@@ -71,9 +90,14 @@ def image(self, content=None, filename=None, source_uri=None):
     def _vision_api(self):
         """Proxy method that handles which transport call Vision Annotate.
 
-        :rtype: :class:`~google.cloud.vision._rest._HTTPVisionAPI`
-        :returns: Instance of ``_HTTPVisionAPI`` used to make requests.
+        :rtype: :class:`~google.cloud.vision._http._HTTPVisionAPI`
+                or :class:`~google.cloud.vision._gax._GAPICVisionAPI`
+        :returns: Instance of ``_HTTPVisionAPI`` or ``_GAPICVisionAPI`` used to
+                  make requests.
         """
         if self._vision_api_internal is None:
-            self._vision_api_internal = _HTTPVisionAPI(self)
+            if self._use_gax:
+                self._vision_api_internal = _GAPICVisionAPI(self)
+            else:
+                self._vision_api_internal = _HTTPVisionAPI(self)
         return self._vision_api_internal

vision/unit_tests/test__gax.py

@@ -0,0 +1,29 @@
+# Copyright 2016 Google Inc.
+#
+# 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.
+
+import unittest
+
+
+class TestGAXClient(unittest.TestCase):
+    def _get_target_class(self):
+        from google.cloud.vision._gax import _GAPICVisionAPI
+        return _GAPICVisionAPI
+
+    def _make_one(self, *args, **kwargs):
+        return self._get_target_class()(*args, **kwargs)
+
+    def test_gax_not_implemented(self):
+        client = object()
+        with self.assertRaises(NotImplementedError):
+            self._make_one(client=client)

vision/unit_tests/test_client.py

@@ -55,6 +55,15 @@ def test_annotate_with_preset_api(self):
         client._vision_api.annotate()
         api.annotate.assert_called_once_with()
 
+    def test_gax_not_implemented_from_client(self):
+        credentials = _make_credentials()
+        client = self._make_one(project=PROJECT, credentials=credentials,
+                                use_gax=None)
+        client._connection = _Connection()
+
+        with self.assertRaises(NotImplementedError):
+            client._vision_api()
+
     def test_face_annotation(self):
         from google.cloud.vision.feature import Feature, FeatureTypes
         from unit_tests._fixtures import FACE_DETECTION_RESPONSE