Create openstack.common.jsonutils.

This patch creates a new module, jsonutils.  It is based on some code
from nova.utils that is used by nova.rpc.  It is being added to
openstack-common as another step toward being able to eventually move
nova.rpc to openstack-common.

This module provides a few things:

1) A handy function for getting an object down to something that can
be JSON serialized.  See to_primitive().

2) Wrappers around loads() and dumps().  The dumps() wrapper will
automatically use to_primitive() for you if needed.

3) This sets up anyjson to use the loads() and dumps() wrappers if
anyjson is available.

Change-Id: I41e5759360d515ed53defe69f3e8247aafbcc83a

1 files changed, 133 insertions, 0 deletions

diff --git a/openstack/common/jsonutils.py b/openstack/common/jsonutils.py
new file mode 100644
index 0000000..fa8b8f9
--- /dev/null
+++ b/openstack/common/jsonutils.py
@@ -0,0 +1,133 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2010 United States Government as represented by the
+# Administrator of the National Aeronautics and Space Administration.
+# Copyright 2011 Justin Santa Barbara
+# 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.
+
+'''
+JSON related utilities.
+
+This module provides a few things:
+
+    1) A handy function for getting an object down to something that can be
+    JSON serialized.  See to_primitive().
+
+    2) Wrappers around loads() and dumps().  The dumps() wrapper will
+    automatically use to_primitive() for you if needed.
+
+    3) This sets up anyjson to use the loads() and dumps() wrappers if anyjson
+    is available.
+'''
+
+
+import datetime
+import inspect
+import itertools
+import json
+
+
+def to_primitive(value, convert_instances=False, level=0):
+    """Convert a complex object into primitives.
+
+    Handy for JSON serialization. We can optionally handle instances,
+    but since this is a recursive function, we could have cyclical
+    data structures.
+
+    To handle cyclical data structures we could track the actual objects
+    visited in a set, but not all objects are hashable. Instead we just
+    track the depth of the object inspections and don't go too deep.
+
+    Therefore, convert_instances=True is lossy ... be aware.
+
+    """
+    nasty = [inspect.ismodule, inspect.isclass, inspect.ismethod,
+             inspect.isfunction, inspect.isgeneratorfunction,
+             inspect.isgenerator, inspect.istraceback, inspect.isframe,
+             inspect.iscode, inspect.isbuiltin, inspect.isroutine,
+             inspect.isabstract]
+    for test in nasty:
+        if test(value):
+            return unicode(value)
+
+    # value of itertools.count doesn't get caught by inspects
+    # above and results in infinite loop when list(value) is called.
+    if type(value) == itertools.count:
+        return unicode(value)
+
+    # FIXME(vish): Workaround for LP bug 852095. Without this workaround,
+    #              tests that raise an exception in a mocked method that
+    #              has a @wrap_exception with a notifier will fail. If
+    #              we up the dependency to 0.5.4 (when it is released) we
+    #              can remove this workaround.
+    if getattr(value, '__module__', None) == 'mox':
+        return 'mock'
+
+    if level > 3:
+        return '?'
+
+    # The try block may not be necessary after the class check above,
+    # but just in case ...
+    try:
+        if isinstance(value, (list, tuple)):
+            o = []
+            for v in value:
+                o.append(to_primitive(v, convert_instances=convert_instances,
+                                      level=level))
+            return o
+        elif isinstance(value, dict):
+            o = {}
+            for k, v in value.iteritems():
+                o[k] = to_primitive(v, convert_instances=convert_instances,
+                                    level=level)
+            return o
+        elif isinstance(value, datetime.datetime):
+            return str(value)
+        elif hasattr(value, 'iteritems'):
+            return to_primitive(dict(value.iteritems()),
+                                convert_instances=convert_instances,
+                                level=level)
+        elif hasattr(value, '__iter__'):
+            return to_primitive(list(value), level)
+        elif convert_instances and hasattr(value, '__dict__'):
+            # Likely an instance of something. Watch for cycles.
+            # Ignore class member vars.
+            return to_primitive(value.__dict__,
+                                convert_instances=convert_instances,
+                                level=level + 1)
+        else:
+            return value
+    except TypeError, e:
+        # Class objects are tricky since they may define something like
+        # __iter__ defined but it isn't callable as list().
+        return unicode(value)
+
+
+def dumps(value):
+    return json.dumps(value, default=to_primitive)
+
+
+def loads(s):
+    return json.loads(s)
+
+
+try:
+    import anyjson
+except ImportError:
+    pass
+else:
+    anyjson._modules.append((__name__, 'dumps', TypeError,
+                                       'loads', ValueError))
+    anyjson.force_implementation(__name__)