fix: dataclass wrapper was not always called (#4484)

changes/4477-PrettyWood.md

@@ -0,0 +1 @@
+fix: dataclass wrapper was not always called

pydantic/dataclasses.py

@@ -34,7 +34,20 @@ validation without altering default `M` behaviour.
 import sys
 from contextlib import contextmanager
 from functools import wraps
-from typing import TYPE_CHECKING, Any, Callable, ClassVar, Dict, Generator, Optional, Type, TypeVar, Union, overload
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    Callable,
+    ClassVar,
+    Dict,
+    Generator,
+    Optional,
+    Set,
+    Type,
+    TypeVar,
+    Union,
+    overload,
+)
 
 from typing_extensions import dataclass_transform
 
@@ -184,7 +197,7 @@ def dataclass(
     def wrap(cls: Type[Any]) -> 'DataclassClassOrWrapper':
         import dataclasses
 
-        if is_builtin_dataclass(cls):
+        if is_builtin_dataclass(cls) and _extra_dc_args(_cls) == _extra_dc_args(_cls.__bases__[0]):  # type: ignore
             dc_cls_doc = ''
             dc_cls = DataclassProxy(cls)
             default_validate_on_init = False
@@ -418,6 +431,14 @@ def _dataclass_validate_assignment_setattr(self: 'Dataclass', name: str, value:
     object.__setattr__(self, name, value)
 
 
+def _extra_dc_args(cls: Type[Any]) -> Set[str]:
+    return {
+        x
+        for x in dir(cls)
+        if x not in getattr(cls, '__dataclass_fields__', {}) and not (x.startswith('__') and x.endswith('__'))
+    }
+
+
 def is_builtin_dataclass(_cls: Type[Any]) -> bool:
     """
     Whether a class is a stdlib dataclass

tests/test_dataclasses.py

@@ -1395,3 +1395,80 @@ def test_extra_forbid_list_error():
         @pydantic.dataclasses.dataclass
         class Foo:
             a: List[Bar(a=1)]
+
+
+def test_parent_post_init():
+    @dataclasses.dataclass
+    class A:
+        a: float = 1
+
+        def __post_init__(self):
+            self.a *= 2
+
+    @pydantic.dataclasses.dataclass
+    class B(A):
+        @validator('a')
+        def validate_a(cls, value):
+            value += 3
+            return value
+
+    assert B().a == 5  # 1 * 2 + 3
+
+
+def test_subclass_post_init_post_parse():
+    @dataclasses.dataclass
+    class A:
+        a: float = 1
+
+    @pydantic.dataclasses.dataclass
+    class B(A):
+        def __post_init_post_parse__(self):
+            self.a *= 2
+
+        @validator('a')
+        def validate_a(cls, value):
+            value += 3
+            return value
+
+    assert B().a == 8  # (1 + 3) * 2
+
+
+def test_subclass_post_init():
+    @dataclasses.dataclass
+    class A:
+        a: int = 1
+
+    @pydantic.dataclasses.dataclass
+    class B(A):
+        def __post_init__(self):
+            self.a *= 2
+
+        @validator('a')
+        def validate_a(cls, value):
+            value += 3
+            return value
+
+    assert B().a == 5  # 1 * 2 + 3
+
+
+def test_subclass_post_init_inheritance():
+    @dataclasses.dataclass
+    class A:
+        a: int = 1
+
+    @pydantic.dataclasses.dataclass
+    class B(A):
+        def __post_init__(self):
+            self.a *= 2
+
+        @validator('a')
+        def validate_a(cls, value):
+            value += 3
+            return value
+
+    @pydantic.dataclasses.dataclass
+    class C(B):
+        def __post_init__(self):
+            self.a *= 3
+
+    assert C().a == 6  # 1 * 3 + 3