JSON endpoint for project is 404 if only yanked releases are available

[di]

From #3709 (comment), it appears that the JSON API for a project is 404 if the only releases available are yanked releases.

E.g. https://pypi.org/pypi/django-twilio2/json should probably look like https://pypi.org/pypi/django-twilio2/0.9.0/json instead of being 404.

[AustinTSchaffer]

@di Do you know if anyone is working on this? I'm interested in taking a crack at it. I'm working through the getting-started and submitting-patches guides, just didn't want to duplicate any efforts.

[di]

It does not appear that anyone is working on this at the moment!

[AustinTSchaffer]

Sweet! I have a hopefully quick followup question about this. In the case where all non-prerelease versions of a package are yanked, but there are prerelease versions available that are not yanked, should this endpoint default to a yanked version or a prerelease version?

I'm currently thinking that this can be fixed by moving the yanked check from the "where" to the "order by" in the json_project method from warehouse/legacy/api/json.py.

https://github.com/AustinTSchaffer/warehouse/commit/2ac42a1a8953b9de3fcfd4418df45336aaa2180f

[di]

Sweet! I have a hopefully quick followup question about this. In the case where all non-prerelease versions of a package are yanked, but there are prerelease versions available that are not yanked, should this endpoint default to a yanked version or a prerelease version?

I think we should return a yanked release only if there are no other non-yanked releases available.

[AustinTSchaffer]

Thanks for all of the swift responses, I believe this is all finalized and ready for review.