Merge pull request #666 from dhermes/lazy-loading-attempt-3

Moving set_default_dataset_id into _implicit_environ.

gcloud/datastore/__init__.py

@@ -46,12 +46,11 @@
   when race conditions may occur.
 """
 
-import os
-
 from gcloud import credentials
 from gcloud.datastore import _implicit_environ
 from gcloud.datastore._implicit_environ import get_default_connection
 from gcloud.datastore._implicit_environ import get_default_dataset_id
+from gcloud.datastore._implicit_environ import set_default_dataset_id
 from gcloud.datastore.api import allocate_ids
 from gcloud.datastore.api import delete
 from gcloud.datastore.api import get
@@ -68,41 +67,6 @@
          'https://www.googleapis.com/auth/userinfo.email')
 """The scopes required for authenticating as a Cloud Datastore consumer."""
 
-_DATASET_ENV_VAR_NAME = 'GCLOUD_DATASET_ID'
-_GCD_DATASET_ENV_VAR_NAME = 'DATASTORE_DATASET'
-
-
-def set_default_dataset_id(dataset_id=None):
-    """Set default dataset ID either explicitly or implicitly as fall-back.
-
-    In implicit case, supports three cases. In order of precedence, the
-    implicit cases are:
-    - GCLOUD_DATASET_ID environment variable
-    - Google App Engine application ID
-    - Google Compute Engine project ID (from metadata server)
-
-    :type dataset_id: string
-    :param dataset_id: Optional. The dataset ID to use as default.
-
-    :raises: :class:`EnvironmentError` if no dataset ID was implied.
-    """
-    if dataset_id is None:
-        dataset_id = os.getenv(_DATASET_ENV_VAR_NAME)
-
-    if dataset_id is None:
-        dataset_id = os.getenv(_GCD_DATASET_ENV_VAR_NAME)
-
-    if dataset_id is None:
-        dataset_id = _implicit_environ.app_engine_id()
-
-    if dataset_id is None:
-        dataset_id = _implicit_environ.compute_engine_id()
-
-    if dataset_id is not None:
-        _implicit_environ._DEFAULTS.dataset_id = dataset_id
-    else:
-        raise EnvironmentError('No dataset ID could be inferred.')
-
 
 def set_default_connection(connection=None):
     """Set default connection either explicitly or implicitly as fall-back.

gcloud/datastore/_implicit_environ.py

@@ -18,6 +18,7 @@
 imply the current dataset ID and connection from the enviroment.
 """
 
+import os
 import socket
 
 from six.moves.http_client import HTTPConnection  # pylint: disable=F0401
@@ -28,6 +29,10 @@
     app_identity = None
 
 
+_DATASET_ENV_VAR_NAME = 'GCLOUD_DATASET_ID'
+_GCD_DATASET_ENV_VAR_NAME = 'DATASTORE_DATASET'
+
+
 class _DefaultsContainer(object):
     """Container for defaults.
 
@@ -90,6 +95,61 @@ def compute_engine_id():
         connection.close()
 
 
+def _determine_default_dataset_id(dataset_id=None):
+    """Determine default dataset ID explicitly or implicitly as fall-back.
+
+    In implicit case, supports four environments. In order of precedence, the
+    implicit environments are:
+
+    * GCLOUD_DATASET_ID environment variable
+    * DATASTORE_DATASET environment variable (for ``gcd`` testing)
+    * Google App Engine application ID
+    * Google Compute Engine project ID (from metadata server)
+
+    :type dataset_id: string
+    :param dataset_id: Optional. The dataset ID to use as default.
+
+    :rtype: string or ``NoneType``
+    :returns: Default dataset ID if it can be determined.
+    """
+    if dataset_id is None:
+        dataset_id = os.getenv(_DATASET_ENV_VAR_NAME)
+
+    if dataset_id is None:
+        dataset_id = os.getenv(_GCD_DATASET_ENV_VAR_NAME)
+
+    if dataset_id is None:
+        dataset_id = app_engine_id()
+
+    if dataset_id is None:
+        dataset_id = compute_engine_id()
+
+    return dataset_id
+
+
+def set_default_dataset_id(dataset_id=None):
+    """Set default dataset ID either explicitly or implicitly as fall-back.
+
+    In implicit case, supports four environments. In order of precedence, the
+    implicit environments are:
+
+    * GCLOUD_DATASET_ID environment variable
+    * DATASTORE_DATASET environment variable (for ``gcd`` testing)
+    * Google App Engine application ID
+    * Google Compute Engine project ID (from metadata server)
+
+    :type dataset_id: string
+    :param dataset_id: Optional. The dataset ID to use as default.
+
+    :raises: :class:`EnvironmentError` if no dataset ID was implied.
+    """
+    dataset_id = _determine_default_dataset_id(dataset_id=dataset_id)
+    if dataset_id is not None:
+        _DEFAULTS.dataset_id = dataset_id
+    else:
+        raise EnvironmentError('No dataset ID could be inferred.')
+
+
 def get_default_connection():
     """Get default connection.