From b100e90119f3a648cb0f5fb08fa9291bd4ccb3c9 Mon Sep 17 00:00:00 2001
From: Eric Jolibois <em.jolibois@gmail.com>
Date: Mon, 5 Sep 2022 15:09:31 +0200
Subject: [PATCH] fix: always call `__post_init__` when set in dataclasses

---
 changes/4477-PrettyWood.md |  1 +
 pydantic/dataclasses.py    |  4 +-
 tests/test_dataclasses.py  | 77 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+), 1 deletion(-)
 create mode 100644 changes/4477-PrettyWood.md

diff --git a/changes/4477-PrettyWood.md b/changes/4477-PrettyWood.md
new file mode 100644
index 00000000000..b74b32380a2
--- /dev/null
+++ b/changes/4477-PrettyWood.md
@@ -0,0 +1 @@
+fix: dataclass wrapper was not always called
diff --git a/pydantic/dataclasses.py b/pydantic/dataclasses.py
index 856c96d18a0..99567182072 100644
--- a/pydantic/dataclasses.py
+++ b/pydantic/dataclasses.py
@@ -184,7 +184,9 @@ def dataclass(
     def wrap(cls: Type[Any]) -> 'DataclassClassOrWrapper':
         import dataclasses
 
-        if is_builtin_dataclass(cls):
+        if is_builtin_dataclass(cls) and not (
+            is_builtin_dataclass(cls.__bases__[0]) and not hasattr(cls.__bases__[0], '__post_init__')
+        ):
             dc_cls_doc = ''
             dc_cls = DataclassProxy(cls)
             default_validate_on_init = False
diff --git a/tests/test_dataclasses.py b/tests/test_dataclasses.py
index f29bdfc3c80..e2027476bc0 100644
--- a/tests/test_dataclasses.py
+++ b/tests/test_dataclasses.py
@@ -1395,3 +1395,80 @@ class Bar:
         @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