openff-units 0.2.1 breaks mypy for openff-models

[dwhswenson]

Not sure if this belongs here or on openff-models, but here's a MCVE:

# file named example.py
from openff.models.types import FloatQuantity
import openff.units  # type: ignore

print(f"{openff.units.__version__=}")
models_quantity: FloatQuantity["kelvin"]

Then, with openff-units 0.2.0 (and openff-models at current release, 0.0.5):

$ python example.py && mypy example.py
openff.units.__version__='0.2.0'
Success: no issues found in 1 source file

With openff-units 0.2.1:

$ python example.py && mypy example.py
openff.units.__version__='0.2.1'
example.py:5: error: Variable "openff.models.types.FloatQuantity" is not valid as a type  [valid-type]
example.py:5: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases
example.py:5: error: Name "kelvin" is not defined  [name-defined]
Found 2 errors in 1 file (checked 1 source file)

see also https://github.com/OpenFreeEnergy/openfe/issues/461

[mattwthompson]

0.2.1 breaks lots of stuff for reasons that have caused me physiological aging (blood pressure, hair loss, etc.). For now the recommendation is to stick to 0.2.0, since I think that works, and we'll have fixes out as soon as we can (one attempt at https://github.com/openforcefield/openff-units/pull/68).

[mattwthompson]

I'm also not sure if this affects both Pint 0.21 and 0.22, but I'm pretty sure one of them works with 0.2.0

[mattwthompson]

With #84 I have it passing on Pint 0.21, 0.22, 0.23

With https://github.com/openforcefield/openff-models/pull/42 it's also passing with Pydantic models. The SomeQuantity['preferred_unit'] paradigm is likely going away, I unfortunately don't think that pattern is future-compatible with how tooling interprets string literals brackets inside of things that look like types.

77 would be my preferred solution but that's around three years out of being compatible with OpenFF's Python support

[mattwthompson]

This still sticks around on the v1 API, it should be gone with v2

$ cat example.py && python example.py && mypy example.py                                                                           14:00:02  ☁  0.2.2 ☂
# file named example.py
import openff.units
import openff.models

from openff.models.types import FloatQuantity
from pydantic.v1 import BaseModel
from openff.units import Quantity

print(f"{openff.units.__version__=}")
print(f"{openff.models.__version__=}")

class Model(BaseModel):
    temperature: FloatQuantity["kelvin"]

print(f"{Model(temperature=Quantity("419.0 kelvin")).temperature=}")
openff.units.__version__='0.2.2'
openff.models.__version__='0.1.2'
Model(temperature=Quantity("419.0 kelvin")).temperature=<Quantity(419.0, 'kelvin')>
example.py:15: error: Variable "openff.models.types.FloatQuantity" is not valid as a type  [valid-type]
example.py:15: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases
example.py:15: error: Name "kelvin" is not defined  [name-defined]
Found 2 errors in 1 file (checked 1 source file)