Keep dict key order for Python 3.7

src/drf_yasg/openapi.py

@@ -10,7 +10,7 @@
 from django.utils.functional import Promise
 from inflection import camelize
 
-from .utils import filter_none, force_real_str
+from .utils import dict_has_ordered_keys, filter_none, force_real_str
 
 try:
     from collections import abc as collections_abc
@@ -145,7 +145,7 @@ def _as_odict(obj, memo):
             result = OrderedDict()
             memo[id(obj)] = result
             items = obj.items()
-            if not isinstance(obj, OrderedDict):
+            if not dict_has_ordered_keys(obj):
                 items = sorted(items)
             for attr, val in items:
                 result[attr] = SwaggerDict._as_odict(val, memo)

src/drf_yasg/utils.py

@@ -1,5 +1,6 @@
 import inspect
 import logging
+import sys
 from collections import OrderedDict
 
 from django.db import models
@@ -389,8 +390,7 @@ def get_produces(renderer_classes):
 
 
 def decimal_as_float(field):
-    """
-    Returns true if ``field`` is a django-rest-framework DecimalField and its ``coerce_to_string`` attribute or the
+    """Returns true if ``field`` is a django-rest-framework DecimalField and its ``coerce_to_string`` attribute or the
     ``COERCE_DECIMAL_TO_STRING`` setting is set to ``False``.
 
     :rtype: bool
@@ -401,8 +401,7 @@ def decimal_as_float(field):
 
 
 def get_serializer_ref_name(serializer):
-    """
-    Get serializer's ref_name (or None for ModelSerializer if it is named 'NestedSerializer')
+    """Get serializer's ref_name (or None for ModelSerializer if it is named 'NestedSerializer')
 
     :param serializer: Serializer instance
     :return: Serializer's ``ref_name`` or ``None`` for inline serializer
@@ -469,3 +468,16 @@ def get_field_default(field):
                 default = serializers.empty
 
     return default
+
+
+def dict_has_ordered_keys(obj):
+    """Check if a given object is a dict that maintains insertion order.
+
+    :param obj: the dict object to check
+    :rtype: bool
+    """
+    if sys.version_info >= (3, 7):
+        # the Python 3.7 language spec says that dict must maintain insertion order.
+        return isinstance(obj, dict)
+
+    return isinstance(obj, OrderedDict)