#21963 Explicitly importing `types_...` modules leads to non-obvious errors Issue created by huonw Describe the bug Importing from a package with name like

types_...

seems to not work, as dependency inference cannot find it automatically. Importing from a type-stub is peculiar, but seems to be necessary when interacting with the AWS ecosystem, and particularly the async

aioboto3

. For instance, as far as I know, this is the best way to annotate this function: from typing import TYPE_CHECKING import aioboto3 if TYPE_CHECKING: from types_aiobotocore_s3.client import S3Client # importing from a type stub! async def make_client(session: aioboto3.Session) -> Iterator[S3Client]: async with aioboto3.client("s3") as client: yield client It looks like a work around is to set

modules

(potentially via

python_requiremnts(module_mapping=...)

) for the type stub target, to make it behave more like a non-stub. There's no evidence of this workaround from the diagnostics. Reproducer: cd $(mktemp -d) cat > pants.toml <<EOF [GLOBAL] pants_version = "2.24.2" backend_packages = [ "pants.backend.python", "pants.backend.python.typecheck.mypy", ] [python] interpreter_constraints = ["CPython==3.10.*"] EOF # start pantsd pants version cat > x.py <<EOF from types_aiobotocore_s3 import S3Client EOF echo "***** Just dependency inference" cat > BUILD <<EOF python_requirement(name="types-aiobotocore-s3", requirements=["types-aiobotocore-s3"]) python_source(name="x", source="./x.py") EOF echo "BUG: no dependency on types_aiobotocore_s3" pants dependencies x.py echo "BUG: fails with 'cannot find ... types_aiobotocore_s3'" pants check x.py echo "***** Workaround: set modules" cat > BUILD <<EOF python_requirement(name="types-aiobotocore-s3", requirements=["types-aiobotocore-s3"], modules=["types_aiobotocore_s3"]) python_source(name="x", source="./x.py") EOF echo "OKAY: dependency listed types_aiobotocore_s3" pants dependencies x.py echo "OKAY: checking passes" pants check x.py Output:

***** Just dependency inference
BUG: no dependency on types_aiobotocore_s3
18:01:22.32 [WARN] Pants cannot infer owners for the following imports in the target //:x:

  * types_aiobotocore_s3.S3Client (line: 1)

If you do not expect an import to be inferrable, add `# pants: no-infer-dep` to the import line. Otherwise, see <https://www.pantsbuild.org/2.24/docs/using-pants/troubleshooting-common-issues#import-errors-and-missing-dependencies> for common problems.


BUG: fails with 'cannot find ... types_aiobotocore_s3'
18:01:23.54 [INFO] Starting: Building requirements_venv.pex
18:01:24.61 [INFO] Completed: Building requirements_venv.pex
18:01:25.73 [ERROR] Completed: Typecheck using MyPy - mypy - mypy failed (exit code 1).
x.py:1: error: Cannot find implementation or library stub for module named "types_aiobotocore_s3"  [import-not-found]
x.py:1: note: See <https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports>
Found 1 error in 1 file (checked 1 source file)


✕ mypy failed.

***** Workaround: set modules
OKAY: dependency listed types_aiobotocore_s3
//:types-aiobotocore-s3
OKAY: checking passes
18:07:53.33 [INFO] Completed: Typecheck using MyPy - mypy - mypy succeeded.
Success: no issues found in 1 source file


✓ mypy succeeded.

Pants version 2.24.2 OS macOS Additional info N/A pantsbuild/pants