python / python/mypy

Using the pre-commit mypy plugin throws internal library errors

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Description

Using the pre-commit implementation of mypy throws an INTERNAL ERROR on a project that was previously working. Note that running the same version of mypy from the command line against the same files (in a devcontainer) works as expected.

Pre-commit project can be found at: https://github.com/pre-commit/pre-commit Version 4.3.0

From the pre-commit configuration: running mypy v1.18.2

To Reproduce

Create python project, configure git and install the pre-commit hook

Expected Behavior

Expected to run mypy testing on changed files as usual.

Actual Behavior

vscode ➜ /workspace/internalapi (internalapi_apm_and_logs) $ pre-commit run mypy
mypy.....................................................................Failed
- hook id: mypy
- exit code: 2

/home/vscode/.cache/pre-commit/repo3uyifmwv/py_env-python3.12/lib/python3.12/site-packages/django-stubs/http/request.pyi:56: error: INTERNAL ERROR -- Please try using mypy master on GitHub:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 1.18.2
Traceback (most recent call last):
  File "mypy/semanal.py", line 7350, in accept
  File "mypy/nodes.py", line 1624, in accept
  File "mypy/semanal.py", line 3272, in visit_assignment_stmt
  File "mypy/semanal.py", line 3806, in process_type_annotation
  File "mypy/semanal.py", line 6996, in defer
AssertionError: Must not defer during final iteration
/home/vscode/.cache/pre-commit/repo3uyifmwv/py_env-python3.12/lib/python3.12/site-packages/django-stubs/http/request.pyi:56: : note: use --pdb to drop into pdb

Your Environment

  • Mypy version used: 1.18.2
  • Mypy command-line flags: --show-traceback, --check-untyped-defs, --ignore-missing-imports, --config-file=pyproject.toml
  • Mypy configuration options from mypy.ini (and other config files):
  • Python version used: 3.12

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the failure with pre-commit run mypy using Python 3.12, mypy 1.18.2, and the listed flags, then compare it with the command-line invocation. Start at the semantic analyzer traceback in mypy/semanal.py and the django-stubs/http/request.pyi:56 annotation. Done means the pre-commit hook completes without the INTERNAL ERROR while checking the same files.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
tooling
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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