Add grpc_helpers.create_channel (#4069)

* Add grpc_helpers.create_channel

* Fix import order

Author: Jon Wayne Parrott

core/google/api/core/helpers/grpc_helpers.py

@@ -18,6 +18,9 @@
 import six
 
 from google.api.core import exceptions
+import google.auth
+import google.auth.transport.grpc
+import google.auth.transport.requests
 
 
 # The list of gRPC Callable interfaces that return iterators.
@@ -102,3 +105,29 @@ def wrap_errors(callable_):
         return _wrap_stream_errors(callable_)
     else:
         return _wrap_unary_errors(callable_)
+
+
+def create_channel(target, credentials=None, scopes=None, **kwargs):
+    """Create a secure channel with credentials.
+
+    Args:
+        target (str): The target service address in the format 'hostname:port'.
+        credentials (google.auth.credentials.Credentials): The credentials. If
+            not specified, then this function will attempt to ascertain the
+            credentials from the environment using :func:`google.auth.default`.
+        scopes (Sequence[str]): A optional list of scopes needed for this
+            service. These are only used when credentials are not specified and
+            are passed to :func:`google.auth.default`.
+        kwargs: Additional key-word args passed to
+            :func:`google.auth.transport.grpc.secure_authorized_channel`.
+
+    Returns:
+        grpc.Channel: The created channel.
+    """
+    if credentials is None:
+        credentials, _ = google.auth.default(scopes=scopes)
+
+    request = google.auth.transport.requests.Request()
+
+    return google.auth.transport.grpc.secure_authorized_channel(
+        credentials, request, target, **kwargs)

core/tests/unit/api_core/helpers/test_grpc_helpers.py

@@ -128,3 +128,44 @@ def test_wrap_errors_streaming(wrap_stream_errors):
 
     assert result == wrap_stream_errors.return_value
     wrap_stream_errors.assert_called_once_with(callable_)
+
+
+@mock.patch(
+    'google.auth.default',
+    return_value=(mock.sentinel.credentials, mock.sentinel.projet))
+@mock.patch('google.auth.transport.grpc.secure_authorized_channel')
+def test_create_channel_implicit(secure_authorized_channel, default):
+    target = 'example.com:443'
+
+    channel = grpc_helpers.create_channel(target)
+
+    assert channel is secure_authorized_channel.return_value
+    default.assert_called_once_with(scopes=None)
+    secure_authorized_channel.assert_called_once_with(
+        mock.sentinel.credentials, mock.ANY, target)
+
+
+@mock.patch(
+    'google.auth.default',
+    return_value=(mock.sentinel.credentials, mock.sentinel.projet))
+@mock.patch('google.auth.transport.grpc.secure_authorized_channel')
+def test_create_channel_implicit_with_scopes(
+        secure_authorized_channel, default):
+    target = 'example.com:443'
+
+    channel = grpc_helpers.create_channel(target, scopes=['one', 'two'])
+
+    assert channel is secure_authorized_channel.return_value
+    default.assert_called_once_with(scopes=['one', 'two'])
+
+
+@mock.patch('google.auth.transport.grpc.secure_authorized_channel')
+def test_create_channel_explicit(secure_authorized_channel):
+    target = 'example.com:443'
+
+    channel = grpc_helpers.create_channel(
+        target, credentials=mock.sentinel.credentials)
+
+    assert channel is secure_authorized_channel.return_value
+    secure_authorized_channel.assert_called_once_with(
+        mock.sentinel.credentials, mock.ANY, target)