feat: supply anonymous credentials under emulator

See: #70.

google/cloud/datastore/client.py

@@ -16,6 +16,7 @@
 import os
 
 import google.api_core.client_options
+from google.auth.credentials import AnonymousCredentials
 from google.cloud._helpers import _LocalStack
 from google.cloud._helpers import _determine_default_project as _base_default_project
 from google.cloud.client import ClientWithProject
@@ -27,9 +28,6 @@
 from google.cloud.datastore.key import Key
 from google.cloud.datastore.query import Query
 from google.cloud.datastore.transaction import Transaction
-from google.cloud.environment_vars import DISABLE_GRPC
-from google.cloud.environment_vars import GCD_DATASET
-from google.cloud.environment_vars import GCD_HOST
 
 try:
     from google.cloud.datastore._gapic import make_datastore_api
@@ -54,13 +52,20 @@
 _DATASTORE_BASE_URL = "https://datastore.googleapis.com"
 """Datastore API request URL base."""
 
+DATASTORE_EMULATOR_HOST = "DATASTORE_EMULATOR_HOST"
+"""Environment variable defining host for datastore emulator server."""
+DATASTORE_DATASET = "DATASTORE_DATASET"
+"""Environment variable defining default dataset ID under GCD."""
+DISABLE_GRPC = "GOOGLE_CLOUD_DISABLE_GRPC"
+"""Environment variable acting as flag to disable gRPC."""
+
 
 _USE_GRPC = _HAVE_GRPC and not os.getenv(DISABLE_GRPC, False)
 
 
 def _get_gcd_project():
     """Gets the GCD application ID if it can be inferred."""
-    return os.getenv(GCD_DATASET)
+    return os.getenv(DATASTORE_DATASET)
 
 
 def _determine_default_project(project=None):
@@ -266,6 +271,15 @@ def __init__(
         _http=None,
         _use_grpc=None,
     ):
+        emulator_host = os.getenv(DATASTORE_EMULATOR_HOST)
+
+        if emulator_host is not None:
+            if credentials is not None:
+                raise ValueError(
+                    "Explicit credentials are incompatible with the emulator"
+                )
+            credentials = AnonymousCredentials()
+
         super(Client, self).__init__(
             project=project,
             credentials=credentials,
@@ -277,14 +291,15 @@ def __init__(
         self._client_options = client_options
         self._batch_stack = _LocalStack()
         self._datastore_api_internal = None
+
         if _use_grpc is None:
             self._use_grpc = _USE_GRPC
         else:
             self._use_grpc = _use_grpc
-        try:
-            host = os.environ[GCD_HOST]
-            self._base_url = "http://" + host
-        except KeyError:
+
+        if emulator_host is not None:
+            self._base_url = "http://" + emulator_host
+        else:
             api_endpoint = _DATASTORE_BASE_URL
             if client_options:
                 if type(client_options) == dict:

tests/system/test_system.py

@@ -25,7 +25,6 @@
 from google.cloud.environment_vars import GCD_DATASET
 from google.cloud.exceptions import Conflict
 
-from test_utils.system import EmulatorCreds
 from test_utils.system import unique_resource_id
 
 from tests.system.utils import clear_datastore
@@ -44,12 +43,19 @@ class Config(object):
 
 
 def clone_client(client):
-    return datastore.Client(
-        project=client.project,
-        namespace=client.namespace,
-        credentials=client._credentials,
-        _http=client._http,
-    )
+    emulator_dataset = os.getenv(GCD_DATASET)
+
+    if emulator_dataset is None:
+        return datastore.Client(
+            project=client.project,
+            namespace=client.namespace,
+            credentials=client._credentials,
+            _http=client._http,
+        )
+    else:
+        return datastore.Client(
+            project=client.project, namespace=client.namespace, _http=client._http,
+        )
 
 
 def setUpModule():
@@ -59,13 +65,9 @@ def setUpModule():
     if emulator_dataset is None:
         Config.CLIENT = datastore.Client(namespace=test_namespace)
     else:
-        credentials = EmulatorCreds()
         http = requests.Session()  # Un-authorized.
         Config.CLIENT = datastore.Client(
-            project=emulator_dataset,
-            namespace=test_namespace,
-            credentials=credentials,
-            _http=http,
+            project=emulator_dataset, namespace=test_namespace, _http=http,
         )
 
 

tests/unit/test_client.py

@@ -52,10 +52,10 @@ def test_no_value(self):
             self.assertIsNone(project)
 
     def test_value_set(self):
-        from google.cloud.datastore.client import GCD_DATASET
+        from google.cloud.datastore.client import DATASTORE_DATASET
 
         MOCK_PROJECT = object()
-        environ = {GCD_DATASET: MOCK_PROJECT}
+        environ = {DATASTORE_DATASET: MOCK_PROJECT}
         with mock.patch("os.getenv", new=environ.get):
             project = self._call_fut()
             self.assertEqual(project, MOCK_PROJECT)
@@ -235,18 +235,33 @@ def test_constructor_use_grpc_default(self):
             )
             self.assertTrue(client4._use_grpc)
 
-    def test_constructor_gcd_host(self):
-        from google.cloud.environment_vars import GCD_HOST
+    def test_constructor_w_emulator_w_creds(self):
+        from google.cloud.datastore.client import DATASTORE_EMULATOR_HOST
 
         host = "localhost:1234"
-        fake_environ = {GCD_HOST: host}
+        fake_environ = {DATASTORE_EMULATOR_HOST: host}
         project = "PROJECT"
         creds = _make_credentials()
         http = object()
 
         with mock.patch("os.environ", new=fake_environ):
-            client = self._make_one(project=project, credentials=creds, _http=http)
-            self.assertEqual(client.base_url, "http://" + host)
+            with self.assertRaises(ValueError):
+                self._make_one(project=project, credentials=creds, _http=http)
+
+    def test_constructor_w_emulator_wo_creds(self):
+        from google.auth.credentials import AnonymousCredentials
+        from google.cloud.datastore.client import DATASTORE_EMULATOR_HOST
+
+        host = "localhost:1234"
+        fake_environ = {DATASTORE_EMULATOR_HOST: host}
+        project = "PROJECT"
+        http = object()
+
+        with mock.patch("os.environ", new=fake_environ):
+            client = self._make_one(project=project, _http=http)
+
+        self.assertEqual(client.base_url, "http://" + host)
+        self.assertIsInstance(client._credentials, AnonymousCredentials)
 
     def test_base_url_property(self):
         from google.cloud.datastore.client import _DATASTORE_BASE_URL