Module '<namespace package>' has no attribute '<module/pkg in namespace>'

[jaraco]

Bug Report

Attempting to run mypy on jaraco.ui, I'm getting an error:

_________________________________________________ jaraco/ui/cmdline.py _________________________________________________
5: error: Module 'jaraco' has no attribute 'text'

Here is the pertinent code, namely:

from jaraco import text

The module text is supplied by a separate package jaraco.text. The jaraco namespace uses the pkgutil style namespaces (mostly for historical reasons as the code is Python 3-only now, but could still interact with older builds).

This issue is related to #9393, although that issue indicates a different failure mode. Also possibly relevant #6385, #7029.

To Reproduce

git clone https://github.com/jaraco/jaraco.ui
cd jaraco.ui
git checkout eacca37
tox -- -k cmdline

Expected Behavior

mypy should recognize working implementations of extant modules and not fail.

Actual Behavior

Error reported above is emitted.

Your Environment

• Mypy version used: 0.790
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files):
  ignore_missing_imports = True
• Python version used: 3.9.0
• Operating system and version: macOS 10.15

[jaraco]

Interestingly, even though I've started running mypy on all of the projects I maintain, including many importing the jaraco.* namespace, only this one line has given me grief, so the issue may be isolated to the from <namespace> import <module> syntax.

[vbarbaresi]

The tox command didn't work for me, I ran pip install . mypy and
python -m mypy . --ignore-missing-imports
Then I was able to reproduce the issue with mypy v0.790

I tried using mypy from the latest master branch: there's a different error pointing to the source of the problem:

python -m mypy . --ignore-missing-imports
venv/lib/python3.8/site-packages/jaraco/__init__.py: error: Duplicate module named 'jaraco' (also at './jaraco/__init__.py')
venv/lib/python3.8/site-packages/jaraco/__init__.py: error: Are you missing an __init__.py?

I traced it back to #9614 (which is related to the issue #6385 you mentioned)

It doesn't really solve the original issue though, it reappears when running:
mypy jaraco/ui/cmdline.py or mypy -p jaraco
Adding --namespace-packages doesn't change anything
I don't know how to fix that, it seems tricky

[hauntsaninja]

This is a duplicate of #9393

[jaraco]

Since my original post, the jaraco namespace has migrated away from pkgutil-style namespaces (to native PEP 420 namespaces).