[issue36077] Inheritance dataclasses fields and default init statement

[Martijn Pieters]

Martijn Pieters <mj at python.org> added the comment:

I've supported people hitting this issue before (see https://stackoverflow.com/a/53085935/100297, where I used a series of mixin classes to make use of the changing MRO when the mixins share base classes, to enforce a field order from inherited classes.

I'd be very much in favour of dataclasses using the attrs approach to field order: any field named in a base class *moves to the end*, so you can 'insert' your own fields by repeating parent fields that need to come later:

@attr.s(auto_attribs=True)
class Parent:
    foo: str
    bar: int
    baz: bool = False


@attr.s(auto_attribs=True)
class Child(Parent):
    spam: str
    baz: bool = False


The above gives you a `Child(foo: str, bar: int, spam: str, baz: bool = False)` object, note that `baz` moved to the end of the arguments.

`dataclasses` currently doesn't do this, so it'd be a breaking change.

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nosy: +mjpieters

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