dataclasses_transform_meta.py

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"""
Tests the dataclass_transform mechanism when it is applied to a metaclass.
"""

# Specification: https://typing.readthedocs.io/en/latest/spec/dataclasses.html#the-dataclass-transform-decorator


from typing import Any, dataclass_transform

class ModelField:
    def __init__(self, *, init: bool = True, default: Any | None = None) -> None:
        ...


def model_field(
    *, init: bool = True, default: Any | None = None, alias: str | None = None
) -> Any:
    ...


@dataclass_transform(
    kw_only_default=True,
    field_specifiers=(ModelField, model_field),
)
class ModelMeta(type):
    not_a_field: str

    def __init__(self, not_a_field: str) -> None:
        self.not_a_field = not_a_field


class ModelBase(metaclass=ModelMeta):
    def __init_subclass__(
        cls,
        *,
        frozen: bool = False,
        kw_only: bool = True,
        order: bool = True,
    ) -> None:
        ...


class Customer1(ModelBase, frozen=True):
    id: int = model_field()
    name: str = model_field()
    name2: str = model_field(alias="other_name", default="None")


# This should generate an error because a non-frozen class cannot
# derive from a frozen one.
class Customer1Subclass(Customer1, frozen=False):  # E
Expected a ty diagnostic for this line
    salary: float = model_field()


class Customer2(ModelBase, order=True):
    id: int
    name: str = model_field(default="None")


c1_1 = Customer1(id=3, name="Sue", other_name="Susan")

# This should generate an error because the class is frozen.
c1_1.id = 4  # E
[invalid-assignment] Property `id` defined in `Customer1` is read-only

# This should generate an error because the class is kw_only.
c1_2 = Customer1(3, "Sue")  # E
[missing-argument] No arguments provided for required parameters `id`, `name`
[too-many-positional-arguments] Too many positional arguments: expected 0, got 2

# OK (other_name is optional).
c1_3 = Customer1(id=3, name="John")

# This should generate an error because comparison methods are
# not synthesized.
v1 = c1_1 < c1_2  # E
[unsupported-operator] Operator `<` is not supported between two objects of type `Customer1`

c2_1 = Customer2(id=0, name="John")

c2_2 = Customer2(id=1)

v2 = c2_1 < c2_2

# This should generate an error because Customer2 supports
# keyword-only parameters for its constructor.
c2_3 = Customer2(0, "John")  # E
[missing-argument] No argument provided for required parameter `id`
[too-many-positional-arguments] Too many positional arguments: expected 0, got 2


@dataclass_transform(frozen_default=True)
class ModelMetaFrozen(type):
    pass


class ModelBaseFrozen(metaclass=ModelMetaFrozen):
    ...


class Customer3(ModelBaseFrozen):
    id: int
    name: str


c3_1 = Customer3(id=2, name="hi")

# This should generate an error because Customer3 is frozen.
c3_1.id = 4  # E
[invalid-assignment] Property `id` defined in `Customer3` is read-only