python / python/mypy

Overlapping modules overloads in `pyproject.toml` result in undefined behavior

Open
#19,314 0 comments 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

bug topic-configuration
Dominant language
Python
Stars
20.6k
Forks
3.3k
PR merge metrics
PR metrics pending

Description

Bug Report

It's unclear from the docs and runtime what the expected behavior is if you define multiple [[tool.mypy.overrides]] with overlapping modules.

To Reproduce

[[tool.mypy.overrides]]
module = [
    "openstack._log",
    "openstack.cloud._baremetal",
    "openstack.common",
    "openstack.common.*",
    "openstack.config",
    "openstack.config.*",
    "openstack.connection",
    "openstack.exceptions",
    "openstack.fields",
    "openstack.format",
    "openstack.proxy",
    "openstack.utils",
    "openstack.version",
    "openstack.warnings",
]
warn_return_any = true
disallow_untyped_decorators = true
disallow_any_generics = true
disallow_subclassing_any = true
disallow_untyped_calls = true
disallow_untyped_defs = true
no_implicit_reexport = true

[[tool.mypy.overrides]]
module = [
    "openstack.cloud._baremetal",
]
# unset 'warn_return_any' since we need to type the proxy classes first
warn_return_any = false

Expected Behavior

I would expect the configuration to layer, with later (in the file) configuration overriding earlier configuration.

Actual Behavior

In my instance, later configuration related to unit tests was ignored. I have no investigated what's happening here though.

Your Environment

  • Mypy version used: mypy 1.16.1
  • Mypy command-line flags: none
  • Mypy configuration options from mypy.ini (and other config files): per above
  • Python version used: python 3.13.3

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 issue with the two overlapping [[tool.mypy.overrides]] blocks in pyproject.toml using mypy 1.16.1, then trace how overlapping module patterns are interpreted. Done means the precedence behavior is defined and matches the expected later-configuration override, with coverage for overlapping modules.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
devtools
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.