`type: ignore` comments on imports of external package lead to `[unused-ignore]` error codes every other run

Bug Report

When running mypy with --warn-unused-ignore --no-namespace-packages --warn-unused-ignores --ignore-missing-imports, putting a type: ignore[attr-defined] on an import will have mypy report an Unused "type: ignore" comment [unused-ignore] every other run, unless the cache is being cleared between runs.

To Reproduce

from opentelemetry.instrumentation.asgi import (  # type: ignore[attr-defined]
    OpenTelemetryMiddleware,
)

(Since this only seems to work with external packages, some setup is required)

1. Run pip install opentelemetry-instrumentation-asgi opentelemetry-distro
2. Add the code snippet below to file.py
3. Run mypy --warn-unused-ignore --no-namespace-packages --warn-unused-ignores --ignore-missing-imports file.py: Observer no error
4. Run mypy --warn-unused-ignore --no-namespace-packages --warn-unused-ignores --ignore-missing-imports file.py: Observe an [unused-ignore] error
5. Run mypy --warn-unused-ignore --no-namespace-packages --warn-unused-ignores --ignore-missing-imports file.py: Observer no error
6. Repeat the cycle as many times as you like :)

When removing the cache between runs, all works well, so I suspect it has something to do with caching.

Your Environment

• Mypy version used: 1.18.2, main
• Mypy command-line flags: --warn-unused-ignore --no-namespace-packages --warn-unused-ignores --ignore-missing-imports
• Mypy configuration options from mypy.ini (and other config files): -
• Python version used: 3.13.7

Reproduisez le résultat alterné avec file.py en utilisant la commande mypy indiquée et l’importation de opentelemetry, puis suivez le traitement lié au cache de l’état de unused-ignore. Ajoutez un test de régression pour les exécutions répétées depuis le cache ; le travail est terminé lorsque la commande ne signale systématiquement aucune erreur [unused-ignore] parasite.