Introduce generic logger type in loggeradapter

[hoefling]

The reason for this PR:

import logging logger = logging.getLogger() adapter = logging.LoggerAdapter(logger, dict()) reveal_type(adapter.logger) adapter.logger.getChild("fizz")

has no issues with mypy, but pyright reports

 /tmp/main.py:5:13 - info: Type of "adapter.logger" is "Logger | LoggerAdapter" /tmp/main.py:6:16 - error: Cannot access member "getChild" for type "LoggerAdapter"   Member "getChild" is unknown (reportGeneralTypeIssues) 

With the proposed changes, pyright is able to infer the correct type of wrapped logger instance.

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

sphinx (https://github.com/sphinx-doc/sphinx.git) - sphinx/util/logging.py: note: In member "handle" of class "SphinxLoggerAdapter": - sphinx/util/logging.py:140:9: error: Item "LoggerAdapter" of "Union[Logger, LoggerAdapter]" has no attribute "handle" porcupine (https://github.com/Akuli/porcupine.git) + porcupine/plugins/langserver.py:129: error: Missing type parameters for generic type "LoggerAdapter" [type-arg] + porcupine/plugins/langserver.py:143: error: Missing type parameters for generic type "LoggerAdapter" [type-arg] + porcupine/plugins/langserver.py:323: error: Missing type parameters for generic type "LoggerAdapter" [type-arg] + porcupine/plugins/langserver.py:724: error: Missing type parameters for generic type "LoggerAdapter" [type-arg] 

[srittau]

Cc @Akuli as someone affected by this change.

[Akuli]

I have some functions that take an argument of type logging.LoggerAdapter, and I just have to change those to logging.LoggerAdapter[logging.Logger].

[hoefling]

@Akuli @srittau is it an issue that one has to distinct between type checking and runtime now? I mean, LoggerAdapter is not subscriptable, so the type has to be either quoted

x: "logging.LoggerAdapter[logging.Logger]" = ...

or aliased via e.g.

if TYPE_CHECKING: import logging LoggerAdapter = logging.LoggerAdapter[logging.Logger] else: from logging import LoggerAdapter x: LoggerAdapter = ...

[srittau]

That's a general issue, but temporary. I would recommend to use from __future__ import annotations if possible or quoting of not possible.

[onursatici]

@srittau @hoefling What would be the recommendation for inheritance? From what I understand importing annotations or quoting would not be as useful here

import logging class Adapter(logging.LoggerAdapter[logging.Logger]): pass

As LoggerAdapter is not subscriptable, this class will fail to initialise

[Akuli]

This is a common problem, and unfortunately it's annoying to deal with. This works, but it's messy and feels like a hack:

import logging from typing import TYPE_CHECKING if TYPE_CHECKING: _LoggerAdapter = logging.LoggerAdapter[logging.Logger] else: _LoggerAdapter = logging.LoggerAdapter class MyAdapter(_LoggerAdapter): pass

Things that would help, but don't exist yet:

• Default values for generics (Defaults for Generics? mypy#4236)
• Pull request to CPython that makes logging.LoggerAdapter generic at runtime (similar PRs have been accepted in the past)

[hauntsaninja]

Linking the relevant section of mypy docs, in case it helps people: https://mypy.readthedocs.io/en/stable/runtime_troubles.html#using-classes-that-are-generic-in-stubs-but-not-at-runtime

[AlexWaygood]

I've opened python/cpython#92129 to add __class_getitem__ to the class in 3.11+.

(Update: merged!)