mypy does not catch string formatting errors in `logging.log` that are listed - not interpolated

[jvanasco]

I could not find the same issue previously reported here, but these concepts are so generic I would not be surprised user-error is the cause of my failed earch.

Bug Report

In the following script, mypy correctly identifies a string formatting error in case B, which uses print

Cases E and F will both raise exceptions and are not caught.

To Reproduce

import logging
log = logging.getLogger(__name__)

a = "1"
b = "2"

print("print.passes A (%s) %s" % (a, b))
try:
    print("print.fail B [mypy catches] (%s) %s" % (a, ))
except TypeError:
    pass

log.critical("log.passes C (%s) %s" % (a, b))
log.critical("log.passes D (%s) %s" , a, b)
log.critical("log.fail E (%s) %s" , (a, b))
log.critical("log.fail F (%s) %s" , a)

Expected Behavior

I expected mypy to catch the string formatting error here.

I understand logging.log works differently and delays the interpolation. it would be nice if mypy could catch the number of arguments passed to logging to hint at a possible error or pass

Actual Behavior

mypy does not catch this

Your Environment

mypy-1.15.0

[sterliakov]

Pylint does this, Ruff does this (PLE1205 and PLE1206, example).

Are you sure it's a reasonable mypy feature? Sounds like a job for linter to me, not for a type checker. Since it's likely a rare usecase to do log.info("Format", *args) with unpacking (I've probably never seen or did that myself), a simple string munging by linter should be good enough...

[jvanasco]

Are you sure it's a reasonable mypy feature?

No, but not for the reasons you shared.

logging._log( works differently than print( - so this Is a different use case. This seems like something might not be typed correctly though. Some debugging print calls got converted into log on a PR, passed mypy and tests, and this doesn't "look" wrong to tired eyes -- so I merged them. Then this broke on CI.