Invalid Dataclass

What it does

Checks for invalid applications of the @dataclass decorator.

Why is this bad?

Applying @dataclass with incompatible arguments raises an exception while creating the class:

• order=True with eq=False
• weakref_slot=True with slots=False
• slots=True when the class already defines __slots__

Applying @dataclass to a class that inherits from NamedTuple, TypedDict, Enum, or Protocol is also invalid:

• NamedTuple and TypedDict classes will raise an exception at runtime when instantiating the class.
• Enum classes with @dataclass are explicitly not supported.
• Protocol classes define interfaces and cannot be instantiated.

Examples

from dataclasses import dataclass
from typing import NamedTuple


@dataclass(order=True, eq=False)  # error: [invalid-dataclass]
class Ordered: ...


@dataclass
class Foo(NamedTuple):  # error: [invalid-dataclass]
    x: int

See: https://docs.python.org/3/library/dataclasses.html#dataclasses.dataclass