Initial Checks

• I have searched GitHub for a duplicate issue and I'm sure this is something new
• I have searched Google & StackOverflow for a solution and couldn't find anything
• I have read and followed the docs and still think this is a bug
• I am confident that the issue is with pydantic (not my code, or another library in the ecosystem like FastAPI or mypy)

Description

post_init and validator are not triggered in the following code. However, uncommenting any of the lines: py_dataclass(D_C_Base) or b: str = "string" solves the issue.
Versions 1.9.x could trigger both post_init and validators without these lines.

Example Code

from dataclasses import dataclass
from pydantic.dataclasses import dataclass as py_dataclass
from pydantic import validator


@dataclass
class D_C_Base:
    a: float = 1.0

# py_dataclass(D_C_Base)

@py_dataclass
class D_C_Child(D_C_Base):
    # b: str = "string"
    
    def __post_init__(self):
        print('POST_INIT')
        
    @validator('a')
    def validate_a(cls, value):
        print(f'Validating "a" is {value}')

d_c_class = D_C_Child()

Python, Pydantic & OS Version

pydantic version: 1.10.1
pydantic compiled: True
install path: C:\Users\TestUser\.conda\envs\py38\Lib\site-packages\pydantic
               python version: 3.8.13 (default, Mar 28 2022, 06:59:08) [MSC v.1916 64 bit (AMD64)]
platform: Windows-10-10.0.22000-SP0
optional deps. installed: ['typing-extensions']

Also,

pydantic version: 1.10.1
pydantic compiled: True
install path: /local/envs/py39_test/lib/python3.9/site-packages/pydantic
               python version: 3.9.1 (default, Dec 11 2020, 14:32:07)  [GCC 7.3.0]
platform: Linux-3.10.0-1160.66.1.el7.x86_64-x86_64-with-glibc2.17
optional deps. installed: ['typing-extensions']

Affected Components

• Compatibility between releases
• Data validation/parsing
• Data serialization - .dict() and .json()
• JSON Schema
• Dataclasses
• Model Config
• Field Types - adding or changing a particular data type
• Function validation decorator
• Generic Models
• Other Model behaviour - construct(), pickling, private attributes, ORM mode
• Settings Management
• Plugins and integration with other tools - mypy, FastAPI, python-devtools, Hypothesis, VS Code, PyCharm, etc.