Parameter init/init_var ignored

[kwist-sgr]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

Passing a parameter marked as init=False (or init_var=False) does not raise an exception

Example Code

#!/usr/bin/env python3.11
from dataclasses import dataclass, field

from pydantic.dataclasses import dataclass as pydantic_dataclass, Field


@dataclass
class D1:
    a: int = field(init=False, default=-1)


@pydantic_dataclass
class D2:
    a: int = field(init=False, default=-1)


@pydantic_dataclass
class D3:
    a: int = Field(init_var=False, default=-1)


def demo(cls):
    try:
        res = cls(a=1)
    except Exception as exc:
        print(exc)
    else:
        print(res)


def main():
    demo(D1)
    demo(D2)
    demo(D3)


if __name__ == '__main__':
    main()

Output:

D1.__init__() got an unexpected keyword argument 'a'
D2(a=1)
D3(a=1)

Python, Pydantic & OS Version

pydantic version: 2.5.2
        pydantic-core version: 2.14.5
          pydantic-core build: profile=release pgo=true
                 install path: /home/user/.virtualenvs/demo/lib/python3.11/site-packages/pydantic
               python version: 3.11.7 (main, Dec  8 2023, 18:56:58) [GCC 11.4.0]
                     platform: Linux-6.2.0-39-generic-x86_64-with-glibc2.35
             related packages: mypy-1.7.1 email-validator-2.1.0.post1 pydantic-settings-2.1.0 typing_extensions-4.9.0

[sydney-runkle]

@kwist-sgr,

The above code snippet is behaving as expected for cases with D1 and D3.

For D1, The init var for a stdlib dataclass field specifies whether or not the given field is included as a parameter to the generated __init__ method. See the docs here.

For D3, the init_var specification is used to note that the field is an init-only field. See these docs for more details.

That being said, I do think there's an issue with case 2. I think we could implement a fix similar to that from this PR: #7827.

Feel free to submit a PR with a fix!

[kwist-sgr]

@sydney-runkle

Do I understand correctly that FieldInfo doesn't currently support init?
And if a PR is created, will this support need to be added?