Don't show deprecation warning without OS

[pjsier]

Closes #2837. Don't show a deprecation warning when an OS isn't present in the PartialTargetTriple. This way running rustup install stable-x86_64 won't throw a warning.

Let me know if there's anything I should change here, thanks!

[kinnison]

I think instead it'd make more sense to fully expand the inputs with the default host setting instead. That way we're actually going to test the compatibility as intended

[pjsier]

Thanks for the review! I'm not sure I'm understanding, do you mean setting the defaults the way it's done here?

rustup/src/dist/dist.rs

Lines 399 to 407 in a9e1989

	// If OS was specified, don't default to host environment, even if the OS matches
	// the host OS, otherwise cannot specify no environment.
	let env = if self.target.os.is_some() {
	self.target.env
	} else {
	self.target.env.or(host_env)
	};
	let arch = self.target.arch.unwrap_or(host_arch);
	let os = self.target.os.unwrap_or(host_os);

[pjsier]

I'm not sure why the macOS build is failing, but I tried to make some updates here. Let me know if this is what you had in mind!

[kinnison]

I think we'd do better to simply ensure we fully resolve the specifiers before calling the function, rather than trying to make more heuristics in the function itself.

[pjsier]

Thanks for taking a look! I think I misunderstood initially, and I missed the resolve method on PartialToolchainDesc before. I think this is more what you had in mind but let me know if it isn't

[kinnison]

That does indeed look closer to what I imagined; I'd like to know for sure that this solves the issue reported in #2837 and #2672 - I'm not currently near a Windows box though, are you? If not we should definitely add a test case into the test suite for this.

[pjsier]

Makes sense, I have a Windows machine but a test case makes sense either way so I added on here. Let me know if the condition is too specific to the error message, but otherwise it seems to work across architectures

[kinnison]

While this is tightly coupled to the error message, that's fine because we can fix the test if we reword the message, thank you for your effort.