[Feature Request] Detect and warn about the TYPE_CHECKING forward reference antipattern in beartype.claw import hooks 🤮 #477
Description
Hello! I decided to try beartype recently (read: today). I'm working on a large codebase with a hand-rolled runtime type checking system, but everything is also type-annotated, so why not use beartype and halve the work?
Unfortunately, I ran into an issue quite quickly (may just be user error!), because of forward references with deferred imports. Here's a quick reproduction:
Module definition
bears/__init__.py
from bears.core import Bearbears/core.py
from typing import TYPE_CHECKING, Optional
import polars as pl
from beartype import beartype
if TYPE_CHECKING:
from bears.persistent import PolarsBear
@beartype
class Bear:
def __init__(self, name: str, bear_type: Optional[str] = None) -> None:
from bears.ephemeral import SpiritBear
from bears.persistent import PolarsBear
self.instance = (
PolarsBear(name, pl.DataFrame())
if bear_type == "polars"
else SpiritBear(name)
)
def manifest(self) -> "PolarsBear":
from bears.persistent import PolarsBear
return PolarsBear(self.instance.name, pl.DataFrame())bears/ephemeral.py
class SpiritBear:
def __init__(self, name: str) -> None:
self.name = name
def __repr__(self):
return f"SpiritBear({self.name})"bears/persistent.py
import polars as pl
class PolarsBear:
def __init__(self, name: str, data: pl.DataFrame) -> None:
self.name = name
self.data = data
def __repr__(self):
return f"PolarsBear({self.name}, {self.data})"Actual error
>>> from bears import Bear
>>> bear = Bear("Berenstain")
>>> bear.manifest()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<@beartype(bears.core.Bear.manifest) at 0x105742340>", line 18, in manifest
File "/Users/deepyaman/github/dagster-io/dagster/.venv/lib/python3.12/site-packages/beartype/_check/forward/reference/fwdrefmeta.py", line 148, in __instancecheck__
return cls.__is_instance_beartype__(obj)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/deepyaman/github/dagster-io/dagster/.venv/lib/python3.12/site-packages/beartype/_check/forward/reference/fwdrefabc.py", line 111, in __is_instance_beartype__
return isinstance(obj, cls.__type_beartype__) # type: ignore[arg-type]
^^^^^^^^^^^^^^^^^^^^^
File "/Users/deepyaman/github/dagster-io/dagster/.venv/lib/python3.12/site-packages/beartype/_check/forward/reference/fwdrefmeta.py", line 304, in __type_beartype__
referee = import_module_attr(
^^^^^^^^^^^^^^^^^^^
File "/Users/deepyaman/github/dagster-io/dagster/.venv/lib/python3.12/site-packages/beartype/_util/module/utilmodimport.py", line 295, in import_module_attr
raise exception_cls(exception_message)
beartype.roar.BeartypeCallHintForwardRefException: Forward reference "PolarsBear" unimportable from module "bears.core".
>>>Expected output
If I comment out the @beartype decorator:
>>> from bears import Bear
>>> bear = Bear("Berenstain")
>>> bear.manifest()
PolarsBear(Berenstain, shape: (0, 0)
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