feat: Add option to convert frozen dataclasses to frozendicts

dataclasses_json/api.py

@@ -69,8 +69,21 @@ def from_dict(cls: Type[A],
                   infer_missing=False) -> A:
         return _decode_dataclass(cls, kvs, infer_missing)
 
-    def to_dict(self, encode_json=False) -> Dict[str, Json]:
-        return _asdict(self, encode_json=encode_json)
+    def to_dict(self,
+                encode_json=False,
+                use_frozendict=False
+                ) -> Dict[str, Json]:
+        """
+        Converts a dataclass object into a dictionary.
+
+        :param use_frozendict: If set to True, frozen dataclasses will be
+        converted to frozendicts instead of normal dicts.
+
+        :returns: A dictionary representation of the dataclass object.
+        """
+        return _asdict(self,
+                       encode_json=encode_json,
+                       use_frozendict=use_frozendict)
 
     @classmethod
     def schema(cls: Type[A],

dataclasses_json/core.py

@@ -14,6 +14,7 @@
 from typing import (Any, Collection, Mapping, Union, get_type_hints,
                     Tuple, TypeVar)
 from uuid import UUID
+from frozendict import frozendict
 
 from typing_inspect import is_union_type  # type: ignore
 
@@ -340,7 +341,7 @@ def _decode_items(type_arg, xs, infer_missing):
     return items
 
 
-def _asdict(obj, encode_json=False):
+def _asdict(obj, encode_json=False, use_frozendict=False):
     """
     A re-implementation of `asdict` (based on the original in the `dataclasses`
     source) to support arbitrary Collection and Mapping types.
@@ -360,8 +361,13 @@ def _asdict(obj, encode_json=False):
 
         result = _handle_undefined_parameters_safe(cls=obj, kvs=dict(result),
                                                    usage="to")
-        return _encode_overrides(dict(result), _user_overrides_or_exts(obj),
-                                 encode_json=encode_json)
+        result = _encode_overrides(dict(result), _user_overrides_or_exts(obj),
+                                   encode_json=encode_json)
+
+        if use_frozendict and obj.__dataclass_params__.frozen:
+            result = frozendict(result)
+
+        return result
     elif isinstance(obj, Mapping):
         return dict((_asdict(k, encode_json=encode_json),
                      _asdict(v, encode_json=encode_json)) for k, v in

setup.py

@@ -20,7 +20,8 @@
         'dataclasses;python_version=="3.6"',
         'marshmallow>=3.3.0,<4.0.0',
         'marshmallow-enum>=1.5.1,<2.0.0',
-        'typing-inspect>=0.4.0'
+        'typing-inspect>=0.4.0',
+        'frozendict>=2.3.8'
     ],
     python_requires='>=3.6',
     extras_require={