Change behavior in utils.import_object().

Fix bug 972859.

Prior to this patch, utils.import_object(foo) and
utils.import_class(foo) would return the same thing if foo was the path
to a class.  This patch changes utils.import_object() to return an
instance of the class, instead, also allowing you to pass in arguments
to the constructor.

This patch also removes the odd behavior of import_object() to be able
to also import a module.  Instead, a new function import_module() has
been added.

Finally, the three import helpers have been moved to a new module,
importutils.

Change-Id: Ia2ea64c965692f8c3a29adec332dd93a83980070

3 files changed, 48 insertions, 23 deletions

diff --git a/openstack/common/importutils.py b/openstack/common/importutils.py
new file mode 100644
index 0000000..b23d6d4
--- /dev/null
+++ b/openstack/common/importutils.py
@@ -0,0 +1,45 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2011 OpenStack LLC.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+"""
+Import related utilities and helper functions.
+"""
+
+import sys
+
+from openstack.common import exception
+
+
+def import_class(import_str):
+    """Returns a class from a string including module and class"""
+    mod_str, _sep, class_str = import_str.rpartition('.')
+    try:
+        __import__(mod_str)
+        return getattr(sys.modules[mod_str], class_str)
+    except (ImportError, ValueError, AttributeError):
+        raise exception.NotFound('Class %s cannot be found' % class_str)
+
+
+def import_object(import_str, *args, **kwargs):
+    """Import a class and return an instance of it."""
+    return import_class(import_str)(*args, **kwargs)
+
+
+def import_module(import_str):
+    """Import a module."""
+    __import__(import_str)
+    return sys.modules[import_str]
diff --git a/openstack/common/middleware/context.py b/openstack/common/middleware/context.py
index be7dafe..b89ca91 100644
--- a/openstack/common/middleware/context.py
+++ b/openstack/common/middleware/context.py
@@ -19,9 +19,9 @@
 Middleware that attaches a context to the WSGI request
 """
 
-from openstack.common import utils
-from openstack.common import wsgi
 from openstack.common import context
+from openstack.common import importutils
+from openstack.common import wsgi
 
 
 class ContextMiddleware(wsgi.Middleware):
@@ -37,7 +37,7 @@ class ContextMiddleware(wsgi.Middleware):
         # Determine the context class to use
         ctxcls = context.RequestContext
         if 'context_class' in self.options:
-            ctxcls = utils.import_class(self.options['context_class'])
+            ctxcls = importutils.import_class(self.options['context_class'])
 
         return ctxcls(*args, **kwargs)
 
diff --git a/openstack/common/utils.py b/openstack/common/utils.py
index f9dfe73..dee09ac 100644
--- a/openstack/common/utils.py
+++ b/openstack/common/utils.py
@@ -23,7 +23,6 @@ import logging
 import os
 import random
 import shlex
-import sys
 
 from eventlet import greenthread
 from eventlet.green import subprocess
@@ -139,22 +138,3 @@ def execute(*cmd, **kwargs):
             #               call clean something up in between calls, without
             #               it two execute calls in a row hangs the second one
             greenthread.sleep(0)
-
-
-def import_class(import_str):
-    """Returns a class from a string including module and class"""
-    mod_str, _sep, class_str = import_str.rpartition('.')
-    try:
-        __import__(mod_str)
-        return getattr(sys.modules[mod_str], class_str)
-    except (ImportError, ValueError, AttributeError):
-        raise exception.NotFound('Class %s cannot be found' % class_str)
-
-
-def import_object(import_str):
-    """Returns an object including a module or module and class"""
-    try:
-        __import__(import_str)
-        return sys.modules[import_str]
-    except ImportError:
-        return import_class(import_str)