Unlock _CFGetCurrentDirectory

[sidepelican]

Motivation

The URL generated using relative path in URL(initWithFilePath:) will have a baseURL of nil.

print(URL(fileURLWithPath: ".").baseURL) // nil
print(URL(fileURLWithPath: ".").absoluteURL) // .

On platforms such as macOS and Linux, CWD is set to baseURL if relativeTo is empty .
It can be seen from the test that baseURL should be exist.
https://github.com/apple/swift-corelibs-foundation/blob/9bcec0584a704e7be374bd5a1efc94adc3ebde7c/Tests/Foundation/Tests/TestURL.swift#L158

I would like to fix this behavior so that baseURL does not become nil.

Cause

I think this is a historically reason. wasi-libc did not support getcwd first era. so the functions that using getcwd are disabled.
because of this, the partial feature of URL(fileURLWithPath: ".") is also disabled.

swift-corelibs-foundation/CoreFoundation/Base.subproj/CFPlatform.c

Lines 63 to 67 in 6c0904e

	#if !TARGET_OS_WASI
	CF_PRIVATE Boolean _CFGetCurrentDirectory(char *path, int maxlen) {
	return getcwd(path, maxlen) != NULL;
	}
	#endif

Solve

Current wasi-libc has getcwd.
WebAssembly/wasi-libc#214

simply, unlock some #if and it works well.

print(URL(fileURLWithPath: ".").baseURL) // Optional(file:///)
print(URL(fileURLWithPath: ".").absoluteURL) // file:///

[kateinoigakukun]

Seems legit to me 👍

[kateinoigakukun]

I think other filesystem related APIs can be also unblocked on WASI 😉