Updating Bucket.exists method to accept a client.

Towards googleapis#952, removing connection from methods / constructors.

Also adding a temporary Bucket._client_or_connection method
to allow switching from an explicit client to an implicit
connection.

gcloud/storage/bucket.py

@@ -95,18 +95,35 @@ def __init__(self, name=None):
     def __repr__(self):
         return '<Bucket: %s>' % self.name
 
-    def exists(self, connection=None):
+    @staticmethod
+    def _client_or_connection(client):
+        """Temporary method to get a connection from a client.
+
+        If the client is null, gets the connection from the environment.
+
+        :type client: :class:`gcloud.storage.client.Client` or ``NoneType``
+        :param client: Optional. The client to use.  If not passed, falls back
+                       to default connection.
+
+        :rtype: :class:`gcloud.storage.connection.Connection`
+        :returns: The connection determined from the ``client`` or environment.
+        """
+        if client is None:
+            return _require_connection()
+        else:
+            return client.connection
+
+    def exists(self, client=None):
         """Determines whether or not this bucket exists.
 
-        :type connection: :class:`gcloud.storage.connection.Connection` or
-                          ``NoneType``
-        :param connection: Optional. The connection to use when sending
-                           requests. If not provided, falls back to default.
+        :type client: :class:`gcloud.storage.client.Client` or ``NoneType``
+        :param client: Optional. The client to use.  If not passed, falls back
+                       to default connection.
 
         :rtype: boolean
         :returns: True if the bucket exists in Cloud Storage.
         """
-        connection = _require_connection(connection)
+        connection = self._client_or_connection(client)
         try:
             # We only need the status code (200 or not) so we seek to
             # minimize the returned payload.

gcloud/storage/test_bucket.py

@@ -125,6 +125,23 @@ def test_ctor_explicit(self):
         self.assertFalse(bucket._default_object_acl.loaded)
         self.assertTrue(bucket._default_object_acl.bucket is bucket)
 
+    def test__client_or_connection_implicit(self):
+        from gcloud._testing import _Monkey
+        from gcloud.storage import bucket as MUT
+        bucket = self._makeOne()
+        num_mock_require_calls = [0]
+        cnxn = object()
+
+        def mock_require():
+            num_mock_require_calls[0] += 1
+            return cnxn
+
+        with _Monkey(MUT, _require_connection=mock_require):
+            result = bucket._client_or_connection(None)
+
+        self.assertTrue(result is cnxn)
+        self.assertEqual(num_mock_require_calls, [1])
+
     def test_exists_miss(self):
         from gcloud.exceptions import NotFound
 
@@ -139,7 +156,8 @@ def api_request(cls, *args, **kwargs):
 
         BUCKET_NAME = 'bucket-name'
         bucket = self._makeOne(BUCKET_NAME)
-        self.assertFalse(bucket.exists(connection=_FakeConnection))
+        client = _Client(_FakeConnection)
+        self.assertFalse(bucket.exists(client=client))
         expected_called_kwargs = {
             'method': 'GET',
             'path': bucket.path,
@@ -164,7 +182,8 @@ def api_request(cls, *args, **kwargs):
 
         BUCKET_NAME = 'bucket-name'
         bucket = self._makeOne(BUCKET_NAME)
-        self.assertTrue(bucket.exists(connection=_FakeConnection))
+        client = _Client(_FakeConnection)
+        self.assertTrue(bucket.exists(client=client))
         expected_called_kwargs = {
             'method': 'GET',
             'path': bucket.path,
@@ -1049,3 +1068,9 @@ class MockFile(io.StringIO):
     def __init__(self, name, buffer_=None):
         super(MockFile, self).__init__(buffer_)
         self.name = name
+
+
+class _Client(object):
+
+    def __init__(self, connection):
+        self.connection = connection