Add support for NixOS

[malaow3]

When trying to invoke sourcekit-lsp on Nix, I get an error:

2024-05-03 14:47:53.510 sourcekit-lsp[25781:4ffff6c0] Could not determine host OS. Falling back to using '.so' as dynamic library extension

Is adding NixOS support a possibility / planned for the future?

[ahoppen]

Looks like we are not detecting NixOS as a Linux OS here:

swift-package-manager/Sources/PackageLoading/Platform.swift

Lines 43 to 53 in 32442c6

	switch try? Process.checkNonZeroExit(args: "uname")
	.trimmingCharacters(in: .whitespacesAndNewlines)
	.lowercased()
	{
	case "darwin"?:
	return .darwin
	case "linux"?:
	return Platform.findCurrentPlatformLinux(localFileSystem)
	default:
	return nil
	}

.

What does uname output on NixOS?

[malaow3]

Here are the results:

uname
Linux

uname -a
Linux nixos 5.15.146.1-microsoft-standard-WSL2 apple/sourcekit-lsp#1 SMP Thu Jan 11 04:09:03 UTC 2024 x86_64 GNU/Linux

[ahoppen]

Synced to Apple’s issue tracker as rdar://127491941

[ahoppen]

Interesting, that definitely is what we are expecting uname to return. In practice, the log message probably shouldn’t cause any issues because we’re falling back to using .so, which is correct for Linux.

Which version of SourceKit-LSP are you using? Ie. which Swift toolchain do you have installed? If it’s some Swift 5 version, could you try if the issue still reproduces with a Swift 6 development snapshot from https://www.swift.org/download/#swift-60-development? I’ve made a lot of improvements to SourceKit-LSP during the Swift 6 development cycle and I vaguely remember seeing that log message before but can’t remember when or if I fixed it.

[malaow3]

I can definitely give that a try, might take me a little bit to figure out how to get everything all set up though

[ahoppen]

Ah, I remember now: I was seeing a similar issue at some point because for some reasons (I can’t remember the details) uname was not in PATH. But that must have been a few years ago and fixed now, even though I don’t remember the fix.

The problem here is that we only detect debian and fedora as Linux distributions here

swift-package-manager/Sources/PackageLoading/Platform.swift

Lines 57 to 77 in 32442c6

	private static func findCurrentPlatformLinux(_ fileSystem: FileSystem) -> Platform? {
	do {
	if try fileSystem.isFile(AbsolutePath(validating: "/etc/debian_version")) {
	return .linux(.debian)
	}
	if try fileSystem.isFile(AbsolutePath(validating: "/system/bin/toolbox")) ||
	fileSystem.isFile(AbsolutePath(validating: "/system/bin/toybox"))
	{
	return .android
	}
	if try fileSystem.isFile(AbsolutePath(validating: "/etc/redhat-release")) ||
	fileSystem.isFile(AbsolutePath(validating: "/etc/centos-release")) ||
	fileSystem.isFile(AbsolutePath(validating: "/etc/fedora-release")) ||
	Platform.isAmazonLinux2(fileSystem)
	{
	return .linux(.fedora)
	}
	} catch {}
	return nil
	}

With that information, it’s not necessary for you to test the Swift 6 snapshot since it also won’t have support for NixOS. I’ll move the issue over to SwiftPM because that’s where the platform detection logic lives.