Allow Private :: Do Not Upload classifier.

[orsinium]

Listing "Private :: Do Not Upload" in the classifiers list is a way to protect a package from accidental uploading on PyPI. This is a special case because it is not listed in the trove classifier.

References:

• Origin: https://twitter.com/di_codes/status/1097220464445931525
• It is implemented on PyPI side: disallow creation of any Classifier with Private at top level pypi/warehouse#5440
• It's not documented yet: Document the "Do not upload" classifier trick packaging.python.org#643
• It is supported by twine: Metadata for upload rejection twine#557

P.S. Sorry for PR without making an issue upfront. I think this is the case that isn't hard to implement, so it's better to show than explain :)

[takluyver]

Thanks, this is an interesting one. The same would work with any invalid classifier, there's nothing particularly special about the name Private :: Do Not Upload. But of course, Flit is deliberately checking if classifiers are valid.

I see from your link that PyPI is essentially promising not to create any Private :: classifier. Maybe Flit should allow any classifiers in that namespace, on the grounds that if you've done that, it's probably deliberate rather than a mistake. Do you know if any other components of the ecosystem have made changes around this idea?

[orsinium]

Maybe Flit should allow any classifiers in that namespace

That would work but I'm for keeping things more strict, there is no reason to have anything different like Private :: Some Explanation Why, additional context can be provided in a comment next to the classifier.

Do you know if any other components of the ecosystem have made changes around this idea?

I don't know any other that checks the classifier on the client-side, TBH. AFAIK, setuptools, poetry, twine, and wheel don't. In dephell, I had only a limited classifier validation as well.

What about usage, GitHub search pops a bit of results:
https://github.com/search?q=%22Private+%3A%3A+Do+Not+Upload%22&type=code
Of course, there won't be much because, well, it's strange to see "private" libraries in public repos :)

[orsinium]

Is there anything I can do to have it merged into the upstream?

[takluyver]

No, I think that's OK, thanks.