consider-using-f-string should not be issued with py-version < 3.6

[scop]

Bug description

f-strings were introduced in Python 3.6, they should not be recommended with earlier py-versions.

Configuration

No response

Command used

echo '"{}".format("foo")' | pylint --py-version=3.5 --from-stdin mymodule | grep f-string

Pylint output

mymodule:1:0: C0209: Formatting a regular string which could be a f-string (consider-using-f-string)

Expected behavior

No consider-using-f-string message when py-version is set to earlier than 3.6.

Pylint version

pylint 2.11.0
astroid 2.8.0
Python 3.9.3 (default, Apr  3 2021, 00:13:19) 
[GCC 9.3.0]

OS / Environment

No response

Additional dependencies

No response

[Pierre-Sassoulas]

Hmm, I don't think pylint is supposed to be able to analyze version < 3.6. The py-version is kinda misleading because it feels like it should work but there was clearly an assumption that python interpreter used == py-version, originally. What do you think @cdce8p ?

[scop]

Hm, not sure what you mean by that assumption. But FWIW the way it's put in the release notes:

Added py-version config key (if [MASTER] section). Used for version dependant checks. Will default to whatever Python version pylint is executed with.

...gives a very strong impression that it actually does work. In my opinion it definitely should :)

BTW the features entry for this option at https://docs.pylint.org/en/latest/technical_reference/features.html?highlight=py-version#general-options is quite confusing:

Min Python version to use for version dependend checks. Will default to the version used to run pylint.
Default: 3.8

It first says default is the version used to run pylint, then it says default is 3.8.
(While at it, I'd suggest rephrasing Min -> Minimum, and fixing dependend -> dependent. Would submit a PR for this but perhaps there will be bigger changes to the doc if I'm not right about what the option is for.)

[cdce8p]

Hmm, I don't think pylint is supposed to be able to analyze version < 3.6. The py-version is kinda misleading because it feels like it should work but there was clearly an assumption that python interpreter used == py-version, originally.

That was my initial though as well. However, it does make sense to extend it to other checks. If I remember correctly we discussed that shortly that users might want this setting to work for other checks as well. I haven't though about consider-using-f-string as I've disabled it for me personally, but that would indeed be a good fit. It shouldn't be too difficult either. Just the question which other checks need to support it as well. I guess new issues is one way to find out, even if unplanned.

FYI: At the moment, py-version is only used in the Typing and CodeStyle extensions.

But FWIW the way it's put in the release notes: ... ...gives a very strong impression that it actually does work. In my opinion it definitely should :)

I agree. That should have been put better into context.

It first says default is the version used to run pylint, then it says default is 3.8.

The docs are autogenerated with Python 3.8. A bit unfortunate if I'm being honest
https://github.com/PyCQA/pylint/blob/da36529a6ae1fb83417e600528692530a27aac1f/pylint/lint/pylinter.py#L475-L484

(While at it, I'd suggest rephrasing Min -> Minimum, and fixing dependend -> dependent. Would submit a PR for this but perhaps there will be bigger changes to the doc if I'm not right about what the option is for.)

Thanks for the suggestion! A PR would be welcome.

[cdce8p]

Opened #5024 that should address the main concern with the consider-using-f-string checker.