Fix processing of dataclasses types

The workaround for

python/cpython#137891

is more complicated than just accessing the __annotations__ of the
dataclass instead of field.type. Indeed one has to also process all the
base classes. Add a test for derived classes as well.

Author: Zahari Kassabov

validobj/tests/test_delayed_dataclasses.py

@@ -1,16 +1,41 @@
 from typing import Any
 import dataclasses
 
-from validobj import parse_input
+import pytest
+
+from validobj import parse_input, ValidationError
 
 @dataclasses.dataclass
 class Linked:
     value: Any
     parents: Linked | list[Linked] | None = None
 
+@dataclasses.dataclass
+class Parent:
+    parent_field: int = 1
+    override_field: str = 'parent'
+
+@dataclasses.dataclass
+class Child(Parent):
+    child_field: int = 2
+    override_field: int = 3
+
 
 def test_delayed_annotations():
     inp = {'value': 1, 'parents': {'value': 2, 'parents': [{'value': 3}, {'value': 4, 'parents': {'value': 5}}]}}
     assert parse_input(inp, Linked).parents.value == 2
 
+def test_derived_dataclasses():
+    inp = {'child_field': 3, 'parent_field': 4, 'override_field': 5}
+    res = parse_input(inp, Child)
+    assert res.child_field == 3
+    assert res.parent_field == 4
+    assert res.override_field == 5
+
+    with pytest.raises(ValidationError):
+        parse_input({'override_field': 'x'}, Child)
+
+
+
+
 

validobj/validation.py

@@ -181,6 +181,21 @@ def _dataclasses_fields(class_or_instance):
         or f._field_type is dataclasses._FIELD_INITVAR
     )
 
+def _dataclass_types(cls):
+    """ Workaround for https://github.com/python/cpython/issues/137891
+
+    Note that, contrary to dataclasses.fields, the annotations for the base fields are
+    not propagated automatically, so they need to be extracted from the base classes.
+    """
+    res = {}
+
+    # Base classes, including current one, from parent to child, excluding object
+    for base in cls.__mro__[1::-1]:
+        if dataclasses.is_dataclass(base):
+            res.update(base.__annotations__)
+
+    return res
+
 
 def _dataclass_required_allowed(fields):
     allowed = set()
@@ -210,7 +225,7 @@ def _parse_dataclass(value, spec):
         f"fields do not match.",
     )
     # Note: We don't use field.type because of https://github.com/python/cpython/issues/137891
-    types = spec.__annotations__
+    types = _dataclass_types(spec)
 
     res = {}
     field_dict = {