Unexpected `[mypy].config_discovery` behavior

[zach-overflow]

Problem Description

The docs for [mypy].config_discovery state:

If true, Pants will include any relevant config files during runs (mypy.ini, .mypy.ini, and setup.cfg).
Use [mypy].config instead if your config is in a non-standard location.

However, the mypy subsystem will only discover mypy configs in the build root, while ignoring any/all mypy configs elsewhere. This contradicts the "pants will include any relevant config files" statement from the quote above.

Additionally, the current behavior of [mypy].config_discovery does not comport with mypy's definition of "config discovery":

By default, mypy will discover configuration files by walking up the file system (up until the root of a repository or the root of the filesystem).

Relevant source code

• Mypy's ConfigFilesRequest construction using discovery patterns only matching the build root.
• The config discovery behavior in the pants.core.util_rules.config_files:find_config_files rule

Pants Version

2.32.0

Additional Info

Some related issues touching on how mypy's config_discovery probably should behave:

• We can/should partition more tools by config (black, flake8, etc...) #17739
• Ability to run different mypy partitions-by-config in different resolves #17749
• I'd like a way to run mypy in multiple configurations via pants check #22403