Preserve order in json_util.dumps, PYTHON-602.

bson/json_util.py

@@ -83,7 +83,7 @@ except ImportError:
         json_lib = False
 
 import bson
-from bson import EPOCH_AWARE, RE_TYPE
+from bson import EPOCH_AWARE, RE_TYPE, SON
 from bson.binary import Binary
 from bson.code import Code
 from bson.dbref import DBRef
@@ -111,6 +111,10 @@ def dumps(obj, *args, **kwargs):
 
     Recursive function that handles all BSON types including
     :class:`~bson.binary.Binary` and :class:`~bson.code.Code`.
+
+    .. versionchanged:: 2.7
+       Preserves order when rendering SON, Timestamp, Code, Binary, and DBRef
+       instances.
     """
     if not json_lib:
         raise Exception("No json library available")
@@ -143,7 +147,7 @@ def _json_convert(obj):
     converted into json.
     """
     if hasattr(obj, 'iteritems') or hasattr(obj, 'items'):  # PY3 support
-        return dict(((k, _json_convert(v)) for k, v in obj.iteritems()))
+        return SON(((k, _json_convert(v)) for k, v in obj.iteritems()))
     elif hasattr(obj, '__iter__') and not isinstance(obj, string_types):
         return list((_json_convert(v) for v in obj))
     try:
@@ -214,22 +218,23 @@ def default(obj):
             flags += "u"
         if obj.flags & re.VERBOSE:
             flags += "x"
-        return {"$regex": obj.pattern,
-                "$options": flags}
+        return SON([("$regex", obj.pattern), ("$options", flags)])
     if isinstance(obj, MinKey):
         return {"$minKey": 1}
     if isinstance(obj, MaxKey):
         return {"$maxKey": 1}
     if isinstance(obj, Timestamp):
-        return {"t": obj.time, "i": obj.inc}
+        return SON([("t", obj.time), ("i", obj.inc)])
     if isinstance(obj, Code):
-        return {'$code': "%s" % obj, '$scope': obj.scope}
+        return SON([('$code', "%s" % obj), ('$scope', obj.scope)])
     if isinstance(obj, Binary):
-        return {'$binary': base64.b64encode(obj).decode(),
-                '$type': "%02x" % obj.subtype}
+        return SON([
+            ('$binary', base64.b64encode(obj).decode()),
+            ('$type', "%02x" % obj.subtype)])
     if PY3 and isinstance(obj, binary_type):
-        return {'$binary': base64.b64encode(obj).decode(),
-                '$type': "00"}
+        return SON([
+            ('$binary', base64.b64encode(obj).decode()),
+            ('$type', "00")])
     if bson.has_uuid() and isinstance(obj, bson.uuid.UUID):
         return {"$uuid": obj.hex}
     raise TypeError("%r is not JSON serializable" % obj)

test/test_json_util.py

@@ -69,7 +69,11 @@ class TestJsonUtil(unittest.TestCase):
         self.round_trip({"ref": DBRef("foo", 5)})
         self.round_trip({"ref": DBRef("foo", 5, "db")})
         self.round_trip({"ref": DBRef("foo", ObjectId())})
-        self.round_trip({"ref": DBRef("foo", ObjectId(), "db")})
+
+        # Check order.
+        self.assertEqual(
+            '{"$ref": "collection", "$id": 1, "$db": "db"}',
+            json_util.dumps(DBRef('collection', 1, 'db')))
 
     def test_datetime(self):
         # only millis, not micros
@@ -126,6 +130,15 @@ class TestJsonUtil(unittest.TestCase):
                 '{"r": {"$regex": ".*", "$options": "ilm"}}',
                 compile_re=False)['r'])
 
+        # Check order.
+        self.assertEqual(
+            '{"$regex": ".*", "$options": "mx"}',
+            json_util.dumps(Regex('.*', re.M | re.X)))
+
+        self.assertEqual(
+            '{"$regex": ".*", "$options": "mx"}',
+            json_util.dumps(re.compile('.*', re.M | re.X)))
+
     def test_minkey(self):
         self.round_trip({"m": MinKey()})
 
@@ -135,6 +148,7 @@ class TestJsonUtil(unittest.TestCase):
     def test_timestamp(self):
         res = json_util.json.dumps({"ts": Timestamp(4, 13)},
                                      default=json_util.default)
+        self.assertEqual('{"ts": {"t": 4, "i": 13}}', res)
         dct = json_util.json.loads(res)
         self.assertEqual(dct['ts']['t'], 4)
         self.assertEqual(dct['ts']['i'], 13)
@@ -164,7 +178,10 @@ class TestJsonUtil(unittest.TestCase):
             json_util.loads('{"bin": {"$type": 0, "$binary": "AAECAwQ="}}'))
 
         json_bin_dump = json_util.dumps(md5_type_dict)
-        self.assertTrue('"$type": "05"' in json_bin_dump)
+        self.assertEqual(
+            '{"md5": {"$binary": "IG43GK8JL9HRL4DK53HMrA==", "$type": "05"}}',
+            json_bin_dump)
+
         self.assertEqual(md5_type_dict,
             json_util.loads('{"md5": {"$type": 5, "$binary":'
                             ' "IG43GK8JL9HRL4DK53HMrA=="}}'))
@@ -186,7 +203,13 @@ class TestJsonUtil(unittest.TestCase):
 
     def test_code(self):
         self.round_trip({"code": Code("function x() { return 1; }")})
-        self.round_trip({"code": Code("function y() { return z; }", z=2)})
+
+        code = Code("return z", z=2)
+        res = json_util.dumps(code)
+        self.assertEqual(code, json_util.loads(res))
+
+        # Check order.
+        self.assertEqual('{"$code": "return z", "$scope": {"z": 2}}', res)
 
     def test_cursor(self):
         db = self.db