Importing from non-py.typed module -> "Module has no attribute" with --strict; mypy still suggests the names it doesn't accept

[sliedes]

To me, this issue has a vague resemblance to #10360. I do not know if it is really related.

With --strict, referring to variables imported from a non-py.typed module in another module causes mypy to output two error messages of the form Module has no attribute A; maybe B? and Module has no attribute B; maybe A?, for the same module. This obviously does not make a whole lot of sense.

I do not know if this applies generally to non-py.typed packages or if there's something special about the diffusers package I used.

How to reproduce

$ pip install diffusers==0.5.1

(see the Environment section for the precise packages installed by this)

# bug.py
from diffusers import StableDiffusionImg2ImgPipeline, StableDiffusionPipeline

# bug2.py
import bug

print(bug.StableDiffusionImg2ImgPipeline)
print(bug.StableDiffusionPipeline)

Actual Behavior

$ mypy --strict bug2.py 
bug.py:1: error: Skipping analyzing "diffusers": module is installed, but missing library stubs or py.typed marker  [import]
bug.py:1: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
bug2.py:3: error: Module has no attribute "StableDiffusionImg2ImgPipeline"; maybe "StableDiffusionPipeline"?  [attr-defined]
bug2.py:4: error: Module has no attribute "StableDiffusionPipeline"; maybe "StableDiffusionImg2ImgPipeline"?  [attr-defined]
Found 3 errors in 2 files (checked 1 source file)

Without --strict, the "Skipping analyzing" error is the only one produced. With --ignore-missing-imports or # type: ignore[import] for the import in bug.py, only the "Module has no attribute" errors are produced.

Expected Behavior

Mypy should

1. Understand that the two attributes exist in the bug module;
2. Even failing (1), not suggest options it thinks don't exist.

So I would expect the "Skipping analyzing" to be the only error message mypy outputs.

Your Environment

• Mypy version used: mypy 0.982 (compiled: yes)
• Mypy command-line flags: --config-file= --strict
• Mypy configuration options from mypy.ini (and other config files): None (--config-file=)
• Python version used: 3.10.8

$ pip freeze
certifi==2022.9.24
charset-normalizer==2.1.1
diffusers==0.5.1
filelock==3.8.0
huggingface-hub==0.10.1
idna==3.4
importlib-metadata==5.0.0
mypy==0.982
mypy-extensions==0.4.3
numpy==1.23.4
packaging==21.3
Pillow==9.2.0
pyparsing==3.0.9
PyYAML==6.0
regex==2022.9.13
requests==2.28.1
tomli==2.0.1
tqdm==4.64.1
typing_extensions==4.4.0
urllib3==1.26.12
zipp==3.9.0

[hauntsaninja]

This is because --strict implies --no-implicit-reexport. Do from diffusers import StableDiffusionImg2ImgPipeline as StableDiffusionImg2ImgPipeline

That said, the error message should clearly be better. #9084 / #9237 improved the error message, but looks like due to various issues with the implementation it doesn't actually trigger on your example. Easy enough to fix though