correct openapi_schema_pydantic schemas breaking changes

  - anyOf, allOf, oneOf now default to `None` instead
    of `[]`

Author: Nementon

openapi_python_client/parser/properties/__init__.py

@@ -9,7 +9,6 @@
     "property_from_data",
 ]
 
-from itertools import chain
 from typing import Any, ClassVar, Dict, Generic, Iterable, Iterator, List, Optional, Set, Tuple, TypeVar, Union
 
 import attr
@@ -352,7 +351,14 @@ def build_union_property(
     *, data: oai.Schema, name: str, required: bool, schemas: Schemas, parent_name: str, config: Config
 ) -> Tuple[Union[UnionProperty, PropertyError], Schemas]:
     sub_properties: List[Property] = []
-    for i, sub_prop_data in enumerate(chain(data.anyOf, data.oneOf)):
+
+    for i, sub_prop_data in enumerate(
+        [
+            data
+            for sublists in filter(lambda x: isinstance(x, Iterable), [[], data.anyOf, data.oneOf])
+            for data in sublists
+        ]
+    ):
         sub_prop, schemas = property_from_data(
             name=f"{name}_type{i}",
             required=required,
@@ -440,7 +446,11 @@ def _property_from_data(
         return _property_from_ref(name=name, required=required, parent=None, data=data, schemas=schemas)
 
     # A union of a single reference should just be passed through to that reference (don't create copy class)
-    sub_data = (data.allOf or []) + data.anyOf + data.oneOf
+    sub_data = [
+        data
+        for sublists in filter(lambda x: isinstance(x, Iterable), [[], data.allOf, data.anyOf, data.oneOf])
+        for data in sublists
+    ]
     if len(sub_data) == 1 and isinstance(sub_data[0], oai.Reference):
         return _property_from_ref(name=name, required=required, parent=data, data=sub_data[0], schemas=schemas)