testing annotated attributes (tests/samples/annotated_attribute.py) with mypy_zope 0.1.3

interface_attribute_annotated.py

"""zope.interface provides an attribute with a type annotation for classes
(requres: python 3.6)
"""
import typing
import zope.interface


class IFoo(zope.interface.Interface):
    f_str: typing.Text = zope.interface.Attribute('String Attr')
    f_str_opt: typing.Optional[typing.Text] = zope.interface.Attribute('Optional String Attr')
    f_int: int = zope.interface.Attribute('Integer Attr')
    f_bar: "IBar" = zope.interface.Attribute('Interface Attr')


class IBar(zope.interface.Interface):
    field = zope.interface.Attribute('Unannotated Attr')


@zope.interface.implementer(IFoo)
class Foo(object):
    pass


@zope.interface.implementer(IBar)
class Bar(object):
    pass


def main() -> None:
    foo = Foo()
    bar = Bar()

    # We can assign anything to abstract attributes
    foo.f_str = "Sample"
    foo.f_str = 10
    foo.f_str_opt = "Sample"
    foo.f_str_opt = None
    foo.f_int = 10
    foo.f_int = None
    foo.f_bar = bar

if __name__ == '__main__':
    main()

"""
<output>
interface_attribute_annotated.py:35: error: Incompatible types in assignment (expression has type "int", variable has type "str")
interface_attribute_annotated.py:39: error: Incompatible types in assignment (expression has type "None", variable has type "int")
</output>
"""