Avoid future breakage of setup.py invokations

[astrojuanlu]

See #8659.

[astrojuanlu]

I don't understand the test failure, seems unrelated?

[astrojuanlu]

Important to note that I don't think this has any downsides. Folks willing to use newer versions of setuptools for some exotic feature will need to switch to PEP-517 build system specification, which would enable pip build isolation. And even if they refuse to do that for some reason, they can always add another requirements.txt layer to install the setuptools version they want (although this is not where the ecosystem is going at all).

On the other hand, @agjohnson suggested capping the version only when method: setuptools, but I don't think it's worth the extra complexity in the code to add another if.

[astrojuanlu]

Would be cool if we could test it with some real-world projects just be safe though.

[astrojuanlu]

xref pypa/setuptools#2904

[humitos]

I don't understand the test failure, seems unrelated?

The test failing is related. Take a look at this line https://app.circleci.com/pipelines/github/readthedocs/readthedocs.org/3393/workflows/481df7c7-8c03-47a7-a85a-5b1e216b3202/jobs/7260?invite=true#step-106-186

It checks for the command executed and it contains setuptools where it should be "setuptools<58.3.0" 😄

[humitos]

I don't have full contex about this because there is too much things involved and too much reading required 😄 --however, it doesn't seem bad to pin setuptools to a version that works. @astrojuanlu, you are my packaging master, so if you say this is correct it is for me 😉

Would be cool if we could test it with some real-world projects just be safe though.

Did we already notice some projects failing because of this? I can help you test this if you want.

[astrojuanlu]

There are no projects failing yet, because the removal hasn't happened. Hmmm I'll think of how we could test it

[astrojuanlu]

Oh thanks for the pointer, there was a huge traceback and I got lost. Addressing.

[astrojuanlu]

I think the only way of effectively demonstrating the effects of not merging this would be to locally replace the deprecation warnings introduced in setuptools 58.3.0 for setup_requires, easy_install, and setup.py install by actual errors and see what would happen. I suspect many old RTD projects would fail immediately.

pypa/setuptools@v58.2.0...v58.3.0

[astrojuanlu]

Added an unrelated commit, but that involves setuptools too.

[stsewd]

We should update https://docs.readthedocs.io/en/stable/builds.html#external-dependencies

[agjohnson]

but I don't think it's worth the extra complexity in the code to add another if

👍 we can iterate later if we need to buy ourselves more time on this deprecation