deprecation attr

[nstarman]

Adds the __deprecated__ attribute.
Also cleans up deprecated so that we don't re-define the helper functions every time deprecated is called.
deprecated still redefines all functions on every call.

[github-actions]

Thank you for your contribution to Astropy! 🌌 This checklist is meant to remind the package maintainers who will review this pull request of some common things to look for.

• Do the proposed changes actually accomplish desired goals?
• Do the proposed changes follow the Astropy coding guidelines?
• Are tests added/updated as required? If so, do they follow the Astropy testing guidelines?
• Are docs added/updated as required? If so, do they follow the Astropy documentation guidelines?
• Is rebase and/or squash necessary? If so, please provide the author with appropriate instructions. Also see instructions for rebase and squash.
• Did the CI pass? If no, are the failures related? If you need to run daily and weekly cron jobs as part of the PR, please apply the "Extra CI" label. Codestyle issues can be fixed by the bot.
• Is a change log needed? If yes, did the change log check pass? If no, add the "no-changelog-entry-needed" label. If this is a manual backport, use the "skip-changelog-checks" label unless special changelog handling is necessary.
• Is this a big PR that makes a "What's new?" entry worthwhile and if so, is (1) a "what's new" entry included in this PR and (2) the "whatsnew-needed" label applied?
• Is a milestone set? Milestone must be set but we cannot check for it on Actions; do not let the green checkmark fool you.
• At the time of adding the milestone, if the milestone set requires a backport to release branch(es), apply the appropriate "backport-X.Y.x" label(s) before merge.

[github-actions]

👋 Thank you for your draft pull request! Do you know that you can use [ci skip] or [skip ci] in your commit messages to skip running continuous integration tests until you are ready?

[pllim]

I didn't expect to see so much diff. I thought it would be a few lines to add a new attribute.

[nstarman]

If you look at 12b5d46, then it's only a few lines.
I just took the opportunity to also clean up the code. Basically I just moved a pile of functions defined inside deprecated out. They were unnecessarily being re-defined every time deprecated was called.

[pllim]

Can we separate the two into different PRs? 🙏

Also I don't think refactoring is necessary given that you already want to replace with yet another implementation down the road.

[nstarman]

Can we separate the two into different PRs? 🙏

Sure.

Also I don't think refactoring is necessary given that you already want to replace with yet another implementation down the road.

This code cleanup / improvement is cherry picked from #15301, which then just changes some more internals to use typing.deprecated.

[pllim]

Much cleaner, thanks! I'll let mhvk review since he requested it.

[mhvk]

Yes, this looks good! Should there be some test, though? E.g., I think it works on attributes indirectly, maybe worthwhile to test? I guess more generally: does it in fact work in your IDE?

[nstarman]

Unfortunately since VSCode's code help is generally powered by static analysis our decorator is not recognized.

Screenshots

Note that VSCode has crossed-out the function as I type it

At least _deprecated__ is attached correctly (see the tests)

[pllim]

I think you need to rebase to pick up RTD fix.

[mhvk]

It might be worth suggesting to VSCode to assume that anything marked by *deprecated* is actually deprecated... Doesn't seem like there would be many false positives!

[mhvk]

Looks good!

[pllim]

Thanks!