``consider-using-f-string`` and ``logging-fstring-interpolation`` are mutually exclusive

[angiarao]

Bug description

Enabling both C0209 (consider-using-f-string) and W1203(logging-fstring-interpolation) causes conflict issues.
If logging is using % formatting, then C0209 error message is throwing on the logging string. Is there a way to avoid this conflict?

Configuration

# Maximum number of nested blocks for function / method body
max-nested-blocks=5

# Disable the message, report, category or checker with the given id(s). You
# can either give multiple identifiers separated by comma (,) or put this
# option multiple times (only on the command line, not in the configuration
# file where it should appear only once).You can also use "--disable=all" to
# disable everything first and then reenable specific checks. For example, if
# you want to run only the similarities checker, you can use "--disable=all
# --enable=similarities". If you want to run only the classes checker, but have
# no Warning level messages displayed, use"--disable=all --enable=classes
# --disable=W"
# Example:
# disable=E1608,W1627,E1601
# we are disabling all warnings as it would create a lot of noise
# we will enable only selected warnings when needed.
disable=all

# Enable the message, report, category or checker with the given id(s). You can
# either give multiple identifier separated by comma (,) or put this option
# multiple time. See also the "--disable" option for examples.
# List of all codes can be found here -
# https://pylint.pycqa.org/en/latest/technical_reference/features.html
# or http://pylint-messages.wikidot.com/all-codes


enable=C0114,C0206,C0209
    ,E0102,E1111,E1120,E1121,E1123,E1305,E1606,E1601
    ,E9004,E9005,E9006,E9007,E9008,E9009,E9010,E9011
    ,E9013,E9014,E9015,E9016
    ,R0912,R1702,R1734
    ,W0101,W0123,W0311,W0612,W0613,W0614,W1620
    ,W9001,W9002,W9003,W9017

Command used

python3 -m pylint --rcfile=.py3lintrc --reports=no --msg-template="{line}|{column}|{msg_id}|{symbol}|{msg}" <filename>

Pylint output

Advice  (C0209) pylint - Consider Using F String
Formatting a regular string which could be a f-string
>>>       62     log.debug('resource %s was discovered' % name)

Warning  (W1203) pylint - Logging Fstring Interpolation
Use lazy % or .format() or % formatting in logging functions
>>>       62     log.debug(f'resource {name} was discovered')

Expected behavior

i think C0209 should be suppressed if the W1203 is enabled.

Pylint version

pylint 2.11.1
astroid 2.8.4
Python 3.6.9 (default, Jan 26 2021, 15:33:00)
[GCC 8.4.0]

OS / Environment

Ubuntu 18.04

Additional dependencies

No response

[Pierre-Sassoulas]

Could probably be a configuration warning so users need to take a decision themselves.

[angiarao]

the problem is for newbie developers and large diffs, it creates a lot of noise. It would be great to disable fstring check for logging statements if W1203 is enabled.

[Pierre-Sassoulas]

I like this, if one of them is explicitly enabled then we disable the other one, if both of them are enabled then we raise a warning.

[fmigneault]

C0209 seems to be a bad side effect here. It should simply be W1203.

Both of these definitions are incorrect according to best practices for logging package:

Advice  (C0209) pylint - Consider Using F String
Formatting a regular string which could be a f-string
>>>       62     log.debug('resource %s was discovered' % name)

Warning  (W1203) pylint - Logging Fstring Interpolation
Use lazy % or .format() or % formatting in logging functions
>>>       62     log.debug(f'resource {name} was discovered')

The correct fix is to use:

log.debug('resource %s was discovered', name)

This is the optimal way because, contrary to the other 2 approaches, passing the parameter allows logging to skip any string formatting if the logger is not level <= DEBUG. The 2 erroneous approaches waste time performing string formatting before logging, even if the message does not even get logged when level > DEBUG.

[Pierre-Sassoulas]

Not wanting to enable W1203 is a user choice, f-strings are efficient and looks better, and the performance increase is low. There was much vitriol in the discussion about this in another issue, so we're going to keep allowing both possibilities. Beside if we want to follow KISS, pylint should not emit message conditionally depending on other message being activated or not.

For someone wanting to implement this it would be nice to have a data structure with mutually exclusive msgid and raise mutually-exclusive-option-value when we encounter two of them activated at once.