Mypy: "Unsupported converter" for completely unanotated function

[dimaqq]

A slightly different case with same error message just popped up with mypy==0.650:

import attr


def foo(value):
    return value.split()


@attr.s
class Bar:
    field = attr.ib(default=None, converter=foo)

> mypy test_mypy.py
test_mypy.py:10: error: Unsupported converter, only named functions and types are currently supported

[ilevkivskyi]

Note that adding at least a single annotation to foo fixed this. It looks like this should be easy to fix.

cc @euresti

[GabrielC101]

Having the same issue with lambdas.

[skhalymon]

How is possible to skip this warning? It appears even in typed functions and it annoys me.

[gvanrossum]

Someone (you?) will have to update the plugin.

[officialcryptomaster]

@ilevkivskyi can you demonstrate how I Can add an annotation to suppress this error?

[officialcryptomaster]

Ah @ilevkivskyi I see you mean this:

import attr

def foo(value) -> str:
    return value.split()

@attr.s
class Bar:
    field = attr.ib(default=None, converter=foo)

[ilevkivskyi]

@officialcryptomaster Yes.

[officialcryptomaster]

Seems like similar issue exists with flake8 which does not go away with type annotations... Any idea how I can work around that one other than suppress it?

[JelleZijlstra]

@officialcryptomaster this sounds like you should report the issue to flake8, unless I'm misunderstanding what you say.

[webknjaz]

This is also happening with annotated functions that use functools.singledispatch().

[madig]

Maybe the warning should read "Unsupported converter, only types and named functions with an annotated return type are currently supported" 🙂

[JarnoRFB]

This somehow seems to be broken for attrs 20.3. For

import attr

def foo(value) -> str:
    return value.split()

@attr.s
class Bar:
    field = attr.ib(default=None, converter=foo)

mypy gives me error: Need type annotation for 'field', while it works with attrs 19.3. Not sure if this issue needs to be addressed in mypy or attrs.

[euresti]

I'm pretty sure this last one is because attrs changed the stubs.