Add LTS to SPEC 0

[jarrodmillman]

See scikit-learn/scikit-learn#30888 (comment).

Todo:

• Get feedback from SPEC committee
• Get scikit-learn feedback
• Get approval from all core projects that currently endorse SPEC 0
• update spec-0000/SPEC0_versions.py

[bsipocz]

I really like phrasing this as LTS, it feels to be a nice extension and compromise!

I haven't looked in into the test failures, obviously the approval is not for any potentially relevant failures.

[virchan]

I think what's outlined in LTS is consistent with what scikit-learn is doing in scikit-learn/scikit-learn#30888.

So I would like to ping @lesteve and @lucascolley to see if they have any thoughts or input.

[mdhaber]

The first sentence is that all projects should adopt a common policy. This goes against that, so I think we should acknowledge the discrepancy in some way. If we do not recommend one over the other, the first sentence might change to be "adopt one of two time-based poicies...". If we have a preference for the first but recognize the need for the other, we might say something to that effect here.

[mdhaber]

Suggestions about the new text are inline.

If we were modifying other text:

• I don't understand the connection between the timeframe over which new releases support old dependency versions and the timeframe over which a given (feature) release will get bug fix releases. I think the SPEC would be more focused if it only mentions the former.
• The "Ecosystem Adoption" and "Implementation" sections are empty. Is that desirable?
• The background and motivation appears at the end, after the policy itself. Was that intentional?
• The SPEC only mentions limiting support duration as a motivation. Does it also recommend providing at least a certain amount of time - just not much more?

But if the intent is to address only LTS here, feel free to hide this comment as "off topic".

[lucascolley]

I agree with Matt's comments, but otherwise this looks like a useful change!

[stefanv]

Observations from discussions here at EuroSciPy:

• The "after the next release" phrasing is confusing.
• With the "after the next" change, doesn't this immediately grow the window, so that the LTS version is now two years longer?
• As a maintainer, it's useful to think in terms of "oldest supported version": i.e., "minimum version of Python should be a bit older than 3 yrs", then look up release dates and find that version of Python. Or, to phrase differently: at the point in time where you need the information, you need to look back, so the forward-looking formulation is confusing.
• May be worth formulating this both in terms of support windows and "today - 3 years, what was released" to match different intuitive approaches. Some people like the graphic approach as-is.
• Can we also visualize LTS on existing plot by shifting the red line?
• Stretch goal: would be nice to have a JS version that fetches release information from PyPi and generates the plot dynamically.

[lucascolley]

Can we also visualize LTS on existing plot by shifting the red line?

A toggle or tab for this would be nice!