Support multiple target versions

[JonathanPlasse]

• To implement RFE: infer target-version from project metadata #2039 we need to support multiple target versions.
• We should use the minimum target version for pyupgrade.
• For isort known standard library, we should check that the module is present for all target version
• …

[charliermarsh]

What's the difference in practice between supporting a minimum version, and a range of versions?

[JonathanPlasse]

For isort known standard library, you could have some modules that are removed for later versions.
If you use the minimum version, you would have a false negative for the later versions if you use a dropped module.

[charliermarsh]

I guess I'm not sure what should happen if you specify that your minimum version is 3.7, and you import tomllib.

[JonathanPlasse]

It should report this as an error as it is not available in the Python 3.7 standard library.

[stinodego]

I know that black is actually trying to get rid of target ranges and wants to switch to a single minimum target version.

I don't think supporting target ranges is worthwhile.

• To implement RFE: infer target-version from project metadata #2039 we need to support multiple target versions.

This is not true - you can infer a minimum target version from the requires-python specifier. That's how I initially implemented it for black, before I learned more about how their target versions work.

[charliermarsh]

Yeah I'd like to only support a minimum target version until convinced otherwise (i.e., until that's proven insufficient).

[charliermarsh]

Closing for now as I'm okay with current behavior (only supporting minimums).