Fix PEP 0673 before 3.11 (#487)

dataclasses_json/core.py

@@ -1,5 +1,6 @@
 import copy
 import json
+import sys
 import warnings
 from collections import defaultdict, namedtuple
 from dataclasses import (MISSING,
@@ -10,7 +11,7 @@
 from decimal import Decimal
 from enum import Enum
 from typing import (Any, Collection, Mapping, Union, get_type_hints,
-                    Tuple, TypeVar)
+                    Tuple, TypeVar, Type)
 from uuid import UUID
 
 from typing_inspect import is_union_type  # type: ignore
@@ -373,6 +374,20 @@ def _decode_item(type_arg, x):
             return _decode_generic(type_arg, x, infer_missing)
         return x
 
+    def handle_pep0673(pre_0673_hint: str) -> Union[Type, str]:
+        for module in sys.modules:
+            maybe_resolved = getattr(sys.modules[module], type_args, None)
+            if maybe_resolved:
+                return maybe_resolved
+
+        warnings.warn(f"Could not resolve self-reference for type {pre_0673_hint}, "
+                      f"decoded type might be incorrect or decode might fail altogether.")
+        return pre_0673_hint
+
+    # Before https://peps.python.org/pep-0673 (3.11+) self-type hints are simply strings
+    if sys.version_info.minor < 11 and type_args is not type and type(type_args) is str:
+        type_args = handle_pep0673(type_args)
+
     if _isinstance_safe(type_args, Collection) and not _issubclass_safe(type_args, Enum):
         return list(_decode_item(type_arg, x) for type_arg, x in zip(type_args, xs))
     return list(_decode_item(type_args, x) for x in xs)

tests/entities.py

@@ -381,3 +381,10 @@ class DataClassWithNestedDictWithTupleKeys:
 @dataclass
 class DataClassWithCounter:
     c: Counter[str]
+
+
+@dataclass_json
+@dataclass
+class DataClassWithSelf(DataClassJsonMixin):
+    id: str
+    ref: Optional['DataClassWithSelf']

tests/test_self.py

@@ -0,0 +1,39 @@
+"""
+ PEP 0673 that allows self-references has only been added in 3.11
+ This suite verifies that we are somewhat able to serde self-referencing classes before 3.11.
+"""
+import json
+from typing import Dict
+
+import pytest
+
+from tests.entities import DataClassWithSelf
+
+
+class TestSelf:
+    @pytest.mark.parametrize("entity, expected", [
+        (DataClassWithSelf(id="1", ref=None), {
+            "id": "1",
+            "ref": None
+        }),
+        (DataClassWithSelf(id="1", ref=DataClassWithSelf(id="2", ref=None)), {
+            "id": "1",
+            "ref": { "id": "2", "ref": None }
+        })
+    ])
+    def test_self_serde(self, entity: DataClassWithSelf, expected: Dict):
+        assert entity.to_dict() == expected and DataClassWithSelf.from_dict(expected).to_json() == entity.to_json()
+
+    @pytest.mark.parametrize("entity", [
+        ({
+            "id": "1",
+            "ref": {"id": "2", "ref": None}
+        }),
+        ({
+            "id": "1",
+            "ref": None
+        })
+    ])
+    def test_self_type(self, entity: Dict):
+        obj = DataClassWithSelf.from_json(json.dumps(entity))
+        assert isinstance(obj, DataClassWithSelf) and (isinstance(obj.ref, DataClassWithSelf) or isinstance(obj.ref, type(None)))