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

2 files changed, 251 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__)
diff --git a/tests/unit/test_jsonutils.py b/tests/unit/test_jsonutils.py
new file mode 100644
index 0000000..084a172
--- /dev/null
+++ b/tests/unit/test_jsonutils.py
@@ -0,0 +1,118 @@
+# 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 datetime
+import unittest
+
+from openstack.common import jsonutils
+
+
+class JSONUtilsTestCase(unittest.TestCase):
+
+    def test_dumps(self):
+        self.assertEqual(jsonutils.dumps({'a': 'b'}), '{"a": "b"}')
+
+    def test_loads(self):
+        self.assertEqual(jsonutils.loads('{"a": "b"}'), {'a': 'b'})
+
+
+class ToPrimitiveTestCase(unittest.TestCase):
+    def test_list(self):
+        self.assertEquals(jsonutils.to_primitive([1, 2, 3]), [1, 2, 3])
+
+    def test_empty_list(self):
+        self.assertEquals(jsonutils.to_primitive([]), [])
+
+    def test_tuple(self):
+        self.assertEquals(jsonutils.to_primitive((1, 2, 3)), [1, 2, 3])
+
+    def test_dict(self):
+        self.assertEquals(jsonutils.to_primitive(dict(a=1, b=2, c=3)),
+                          dict(a=1, b=2, c=3))
+
+    def test_empty_dict(self):
+        self.assertEquals(jsonutils.to_primitive({}), {})
+
+    def test_datetime(self):
+        x = datetime.datetime(1, 2, 3, 4, 5, 6, 7)
+        self.assertEquals(jsonutils.to_primitive(x),
+                          "0001-02-03 04:05:06.000007")
+
+    def test_iter(self):
+        class IterClass(object):
+            def __init__(self):
+                self.data = [1, 2, 3, 4, 5]
+                self.index = 0
+
+            def __iter__(self):
+                return self
+
+            def next(self):
+                if self.index == len(self.data):
+                    raise StopIteration
+                self.index = self.index + 1
+                return self.data[self.index - 1]
+
+        x = IterClass()
+        self.assertEquals(jsonutils.to_primitive(x), [1, 2, 3, 4, 5])
+
+    def test_iteritems(self):
+        class IterItemsClass(object):
+            def __init__(self):
+                self.data = dict(a=1, b=2, c=3).items()
+                self.index = 0
+
+            def __iter__(self):
+                return self
+
+            def next(self):
+                if self.index == len(self.data):
+                    raise StopIteration
+                self.index = self.index + 1
+                return self.data[self.index - 1]
+
+        x = IterItemsClass()
+        ordered = jsonutils.to_primitive(x)
+        ordered.sort()
+        self.assertEquals(ordered, [['a', 1], ['b', 2], ['c', 3]])
+
+    def test_instance(self):
+        class MysteryClass(object):
+            a = 10
+
+            def __init__(self):
+                self.b = 1
+
+        x = MysteryClass()
+        self.assertEquals(jsonutils.to_primitive(x, convert_instances=True),
+                          dict(b=1))
+
+        self.assertEquals(jsonutils.to_primitive(x), x)
+
+    def test_typeerror(self):
+        x = bytearray  # Class, not instance
+        self.assertEquals(jsonutils.to_primitive(x), u"<type 'bytearray'>")
+
+    def test_nasties(self):
+        def foo():
+            pass
+        x = [datetime, foo, dir]
+        ret = jsonutils.to_primitive(x)
+        self.assertEquals(len(ret), 3)
+        self.assertTrue(ret[0].startswith(u"<module 'datetime' from "))
+        self.assertTrue(ret[1].startswith('<function foo at 0x'))
+        self.assertEquals(ret[2], '<built-in function dir>')