Docs builds failing

[jaraco]

Since #1981, the docs builds are failing due to 'bootstrap' not having been executed.

When builds were passing previously, they were passing because pip_install: false prevented any attempt to install the package.

[jaraco]

I can imagine a few approaches that would correct the situation:

• restore the prior behavior where docs requirements aren't declared as metadata extras.
• duplicately declare the docs requirements in the file, as before (and keep them in sync going forward).
• enable implicit bootstrapping in setup.py.
• find a hook in rtd that enables the bootstrapping step.

Those are in reverse order of my preference.

The latter two options are the only ones that would support building any docs that reference the source code. In other words, the first two options only work because they avoid the setuptools code base.

Option (4) is not readily viable, but might be through a custom builder.

[jaraco]

The custom build process only hooks into the clean and build steps. It doesn't affect the checkout/install aspects.

[jaraco]

In 1b85cac, I'm exploring option 3. I'm actually liking how much cruft that removes. I'm a little uneasy changing the install process at such an early state, but perhaps it's sufficient. If the tests pass and the docs build, I'm inclined to go with it.

[jaraco]

Looks like that approach isn't quite right.

[jaraco]

In this build, relying on jaraco.packaging 8.1, the issue is more apparent:

ValueError: ('Unexpected metadata output', 'Adding minimal entry_points.\nsetuptools\n45.2.0\nhttps://github.com/pypa/setuptools\nPython Packaging Authority\n')

Adding the implicit bootstrap step (with its output), sullies the clean output of setup.py --name.

[jaraco]

After running into some rather complicated issues, I'm ready to abandon the implicit bootstrap technique. In particular, given the variety of supported invocations of setup.py, including pep517 where build_meta._BuildMetaBackend.run_setup invokes setup.py in-process, it proves tricky to ensure that the metadata is present at the proper time (the 'working set' has already been computed not including anything for setuptools, so even though the entry points are generated just in time, they're not necessarily available).