Handle safe_copy failing to hardlink on Windows due to too many existing links

[akrieger]

Windows does support hard links, and os.link() supports Windows as of Python 3.2. There is a specific error that can be thrown on Windows when you try to create too many hardlinks to a file. Handle that case explicitly in its own test. It's more precise than trying to infer an errno for it which may be mapped to by various kinds of errors.

[jsirois]

@akrieger thanks for the effort here. Much more is required however. In short, Pex does not support Windows yet. There is more recent commentary here: #259 (comment) but one very broken thing is file locking which Pex relies on in its cache handling. That is currently Posix-only. There are many other issues though, including handling venv .exe console script wrappers and more.

My basic stance is that I need green CI on a platform to support that platform. We don't have CI setup for Windows yet. I put a fair chunk of effort towards this in https://github.com/jsirois/pex/tree/Windows/wip ~2 years ago. I'm picking that up again, but you'll truly know when Pex supports Windows by looking here in the "Operating System" section: https://pypi.org/project/pex/ (or here:

pex/pyproject.toml

Lines 38 to 40 in 1921ba4

	"Operating System :: Unix",
	"Operating System :: POSIX :: Linux",
	"Operating System :: MacOS :: MacOS X",

)

[akrieger]

Well, I wrote this because it fixed an issue we were having and I wanted to make sure no one else it hit too. When the project is ready to merge this, it'll be available.

[jsirois]

Thanks. I'll make sure to include this in the initial Windows support release.

Well, I wrote this because it fixed an issue we were having and I wanted to make sure no one else it hit too.

The thing is, no one at all should be using Pex on Windows right now. I can't support it sanely without (green) CI or a Windows-using prospective Pex user providing that green CI baseline.