an option to use the currently executing python version to determine what the rewrite target is

[asottile]

discussed a bit with @hynek on twitter -- mostly need to bikeshed a name

basically an alternative to the --py36-plus options but instead uses the currently running python

[hynek]

For posterity: my main motivation here is that I use pyupgrade 100% via pre-commit and currently have to change both the default Python version to run all tools and the target version for pyupgrade whenever I upgrade an app to a newer Python version.

[lev-blit]

maybe have a fallback of detected version if no --py36-plus option is specified?
seems like changing the min_version argument to have a default of sys.version_info[0:2] would do the trick

[asottile]

no, unexplainable implicit behaviours are bad -- this will be an explicit setting

[lev-blit]

perhaps a mutually exclusive option named --detect-version?

[DjLegolas]

I think that we can use a parameter --currpy-plus which will set min_version = sys.version_info[:2].
The name is still not final 🤣
Something like:

    parser.add_argument(
        '--currpy-plus',
        action='store_const', dest='min_version', const=sys.version_info[:2],
    )

[hynek]

OK I think I would like to modify my feature request!

pyupgrade --requires-python-plus that looks at my packaging metadata and uses the requires-python field – for all I care just by parsing pyproject.toml and setup.cfg. That's what Black is doing now and kinda is what one would expect? I would go as far as saying that should be the default.

[hugovk]

Using requires-python from pyproject.toml would be nice but it's been rejected before (#688 (comment)):

no thanks -- that would involve reading configuration files of which I don't want anything to do with that complexity

Also:

• Use pyproject.toml as alternative to command line args #511
• Support setting default options via pyproject.toml #550
• Use pyproject.toml requires-python field to guess Python target #795