Mypy complains about PyObject

[slafs]

Question

Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":

             pydantic version: 1.4
            pydantic compiled: False
                 install path: /Users/slafs/.pyenv/versions/3.8.1/envs/tapper-core-py38/lib/python3.8/site-packages/pydantic
               python version: 3.8.1 (default, Feb 11 2020, 12:59:26)  [Clang 10.0.1 (clang-1001.0.46.4)]
                     platform: macOS-10.15.4-x86_64-i386-64bit
     optional deps. installed: ['typing-extensions']

I was wondering how can I get mypy to validate the following snippet and at the same time get the fantastic feature of PyObject in my BaseSettings class.

from datetime import date

from pydantic import BaseSettings, PyObject


class MyConf(BaseSettings):
    str_pyobject: PyObject = 'datetime.date'
    callable_pyobject: PyObject = date


conf = MyConf()

var1: date = conf.str_pyobject(2020, 12, 20)
var2: date = conf.callable_pyobject(2111, 1, 1)

print(var1, var2)

I've configured the pydantic mypy pluging the way described in https://pydantic-docs.helpmanual.io/mypy_plugin/.

But mypy complains with:

pyobject_fiddle.py:6: error: Incompatible types in assignment (expression has type "str", variable has type "PyObject")
pyobject_fiddle.py:7: error: Incompatible types in assignment (expression has type "Type[date]", variable has type "PyObject")
pyobject_fiddle.py:12: error: "PyObject" not callable
pyobject_fiddle.py:13: error: "PyObject" not callable
Found 4 errors in 1 file (checked 1 source file)

I tried to fix the errors by subclassing PyObject and creating my own custom type like this:

class MyPyObj(PyObject):

    def __call__(self, *args: Any, **kwargs: Any) -> Any:
        pass

MyPyObjType = Union[MyPyObj, str, Callable[..., Any]]

which almost works, but then I get errors about the var1 and var2 assignements:

pyobject_fiddle.py:21: error: "str" not callable
pyobject_fiddle.py:22: error: "str" not callable

So, I'm not sure what would be the best approach/fix here? BTW is this a pydantic "bug" in any way?

[samuelcolvin]

Thanks for reporting, and sorry for the slow reply.

I'd welcome a PR to "fix" this by adding the above __call__ method and making sure it doesn't break again by adding this example to mypy tests.

[simkimsia]

Is this an easy fix for a first time contributor? If so I like to volunteer 👋