Windows #hostPreopen causes all drive paths to be error

[oovm]

This logic is not correct on Windows, as nodejs does not support drive letters starting with // or \\\\

jco/packages/preview2-shim/lib/nodejs/filesystem.js

Lines 532 to 541 in 46e729c

	if (descriptor.#hostPreopen)
	return (
	descriptor.#hostPreopen +
	(descriptor.#hostPreopen.endsWith("/")
	? ""
	: subpath.length > 0
	? "/"
	: "") +
	subpath
	);

here #hostPreopen = '//' in default case on windows, leads all drive path start with //.

---

We can use the following code as a quick test:

// PS C:\> node -v                                                                    
// v22.12.0
import {opendir} from "node:fs/promises";

const dir1 = await opendir("C:\\")
const dir2 = await opendir("\\\\C:\\") // error

const dir3 = await opendir("C:/")
const dir4 = await opendir("//C:/")    // error

node:fs:561
  return binding.open(
                 ^

Error: UNKNOWN: unknown error, open '//C:/'
    at openSync (node:fs:561:18)
    at Descriptor.openAt (file:///@bytecodealliance/preview2-shim/lib/nodejs/filesystem.js:374:18)
    at wasm://wasm/87d42ad6:wasm-function[21]:0x293
    at wasm://wasm/4fc715b2:wasm-function[77]:0x3004
    at wasm://wasm/87d42ad6:wasm-function[5]:0x1c7
    at wasm://wasm/013b0f46:wasm-function[1623]:0x15797e
    at wasm://wasm/013b0f46:wasm-function[166]:0x4de15
    at wasm://wasm/013b0f46:wasm-function[152]:0x4a64b
    at wasm://wasm/013b0f46:wasm-function[1605]:0x154f49 {
  errno: -4094,
  code: 'UNKNOWN',
  syscall: 'open',
  path: '\\\\C:\\'
}

[guybedford]

Currently we recommend forward-slash UNC paths like //?/C:/Path/To/File.txt for Windows paths. Personally I think that's the better cross platform technique, but I know it's not for everyone. Fully supporting non-UNC Windows paths is still a TODO in the WASI implementation.