Add implicit connection/project support to Topic ctor.

Author: tseaver

gcloud/pubsub/test_topic.py

@@ -25,11 +25,17 @@ def _makeOne(self, *args, **kw):
         return self._getTargetClass()(*args, **kw)
 
     def test_ctor_wo_inferred_project_or_connection(self):
+        from gcloud._testing import _monkey_defaults as _monkey_base_defaults
+        from gcloud.pubsub._testing import _monkey_defaults
         TOPIC_NAME = 'topic_name'
-        topic = self._makeOne(TOPIC_NAME)
+        PROJECT = 'PROJECT'
+        conn = _Connection()
+        with _monkey_base_defaults(project=PROJECT):
+            with _monkey_defaults(connection=conn):
+                topic = self._makeOne(TOPIC_NAME)
         self.assertEqual(topic.name, TOPIC_NAME)
-        self.assertEqual(topic.project, None)
-        self.assertEqual(topic.connection, None)
+        self.assertEqual(topic.project, PROJECT)
+        self.assertTrue(topic.connection is conn)
 
     def test_ctor_w_explicit_project_and_connection(self):
         TOPIC_NAME = 'topic_name'

gcloud/pubsub/topic.py

@@ -16,7 +16,9 @@
 
 import base64
 
+from gcloud._helpers import get_default_project
 from gcloud.exceptions import NotFound
+from gcloud.pubsub._implicit_environ import get_default_connection
 
 
 class Topic(object):
@@ -40,6 +42,10 @@ class Topic(object):
                         environment.
     """
     def __init__(self, name, project=None, connection=None):
+        if project is None:
+            project = get_default_project()
+        if connection is None:
+            connection = get_default_connection()
         self.name = name
         self.project = project
         self.connection = connection