Mypy with in-project virtualenv misses type errors on full path to file

[Doekeb]

Prerequisites

• Poetry version: 1.2.2

• Python version: 3.10.7

• OS version and name: Manjaro Linux (rolling release)

• pyproject.toml: https://gist.github.com/Doekeb/587f55d167c48654b279fde4e7334efb

• Full MWE: Here

• I am on the latest stable Poetry version, installed using a recommended method.

• I have searched the issues of this repo and believe that this is not a duplicate.

• I have consulted the FAQ and blog for any relevant entries or release notes.

• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option) and have included the output below.

Issue

Under specific, but not-so-rare conditions, mypy mistakenly reports that there are no issues in the source file.

Steps to reproduce:

From Scratch:

1. Create a new poetry project with poetry new.
2. poetry config virtualenvs.in-project true --local.
3. Create a simple main.py file inside the package with type annotations and an obvious violation.
4. poetry install.
5. Verify that poetry run mypy poetry_mypy_demo/main.py correctly produces a type error.
6. Either poetry run mypy /full/path/to/package/main.py or poetry shell then mypy /full/path/to/package/main.py.

From MWE:

1. Clone the MWE https://github.com/Doekeb/poetry-mypy-demo.
2. Note, crucially, the setting virtualenvs.in-project = true as defined in poetry.toml.
3. Note, also crucially, that poetry_mypy_demo/main.py has an obvious type violation.
4. poetry install.
5. Verify that poetry run mypy poetry_mypy_demo/main.py correctly produces a type error.
6. Either poetry run mypy /full/path/to/directory/poetry_mypy_demo/main.py or poetry shell then mypy /full/path/to/directory/poetry_mypy_demo/main.py.

Expected Behavior:

Mypy produces the same type error as in step 5.

Actual Behavior:

Mypy finishes successfully without producing any type errors with the message Success: no issues found in 1 source file.

Notes

• There is no bug if step 2 is omitted. In this case, mypy correctly produces a type error when using either the relative or absolute path.
• There is no bug if mypy is installed into an old-school virtual environment (pyenv + virtualenv + pip). This is the main reason that I suspect this is an issue with poetry and not with mypy.
• While the conditions to reproduce this bug are very specific, this situation arises in a very typical workflow: when using VSCode, it is convenient to have virtual environments in-project since they are more easily discovered by the editor. From there, when using mypy as a linter, VSCode calls mypy in the virtual environment on the full path to the file rather than the relative path, and therefore all the conditions to reproduce the bug are present so no linting occurs even with obvious type errors.

Output of mypy -vvv ...

After poetry shell...

• After rm -r .mypy_cache: output of mypy -vvv /full/path/to/directory/poetry_mypy_demo/main.py: https://gist.github.com/Doekeb/9063526e8dce99e5e089ef8f06655a5c
• After rm -r .mypy_cache: output of mypy -vvv poetry_mypy_demo/main.py: https://gist.github.com/Doekeb/b3e8d112e531cdf3d82237e568d1c30b

[neersighted]

Duplicate of a mypy issue: python/mypy#14042

This reproduces without Poetry in the loop; simply poetry install then source .venv/bin/activate; the same symptoms will be exhibited. The same is also the case if you poetry export and install into a virtual environment created with venv and pip.

[github-actions]

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