Improve typehint

[heckad]

No description provided.

[lovasoa]

Is this annotation correct though ? The object returned by this function is a class that inherits from T_SchemaType, not T_SchemaType itself...

[heckad]

This function should return the same type that sanded throw base_schema. If base_schema is None then return default type.

[lovasoa]

Yes, I understand the problem with the two different overloads for this function. However, I don't think the type annotation you added is correct. The type of base_schema and the output type of the function are not the same.

[lovasoa]

Can you give context about why this is needed ?

[heckad]

import typing
from dataclasses import dataclass
from typing import Union

import marshmallow_dataclass
from marshmallow import Schema as BaseSchema
from marshmallow import SchemaOpts as BaseSchemaOpts
from marshmallow import types


class SchemaOpts(BaseSchemaOpts):
    def __init__(self, meta, **kwargs):
        super().__init__(meta, **kwargs)
        self.required_fields = getattr(meta, "required_fields", set())


class MySchema(BaseSchema):
    OPTIONS_CLASS = SchemaOpts

    def __init__(self, *, required_fields=set(), **kwargs):
        self.required_fields = required_fields or self.opts.required_fields
        super().__init__(**kwargs)

    def on_bind_field(self, field_name, field_obj):
        super().on_bind_field(field_name, field_obj)
        if field_name in self.required_fields:
            field_obj.required = True

    def make_data_class(self, data, **_):
        super().make_data_class(data, **_)

    def loads(
        self,
        json_data: Union[str, bytes, bytearray],
        *,
        many: bool = None,
        partial: typing.Union[bool, types.StrSequenceOrSet] = None,
        unknown: str = None,
        **kwargs
    ):
        return super().loads(
            json_data,  # type: ignore
            many=many, partial=partial, unknown=unknown, **kwargs)


@dataclass
class A:
    a: int


schema = marshmallow_dataclass.class_schema(A, base_schema=MySchema)
schema().loads(b'')

Mypy output

test.py:52: error: Argument 1 to "loads" of "Schema" has incompatible type "bytes"; expected "str"
Found 1 error in 1 file (checked 1 source file)

Thats because mypy thing that schema have type Schema instead of MySchema

[lovasoa]

Also, can you fix the tests ? You can run pre-commit to check your work before pushing it.

[heckad]

Done

[heckad]

Thanks a lot!

[lovasoa]

@heckad : I'm trying to write tests for this and it doesn't seem to be supported by mypy, though...

error: Unsupported type Type[T_Schema?]

python/mypy#4300

[lovasoa]

This makes me think we should probably wait for python/mypy#4300 (opened in 2017) to be fixed before merging this PR. The Unsupported type Type[T_Schema?] cannot be silenced, so I fear merging this may cause a lot of trouble to users...

[lovasoa]

type hints should have been fixed