feature request: Implement both path_remove_directory and path_unlink_file

[HarikrishnanBalagopal]

Feature Request

We are implementing 2 of the syscalls that deal with removing files and empty directories.

browser_wasi_shim/src/fd.ts

Lines 99 to 101 in 7349f7d

	path_remove_directory(path): number {
	return -1;
	}

browser_wasi_shim/src/fd.ts

Lines 108 to 110 in 7349f7d

	path_unlink_file(path): number {
	return -1;
	}

https://wasix.org/docs/api-reference/wasi/path_unlink_file
https://wasix.org/docs/api-reference/wasi/path_remove_directory

Status

We have implemented both and it seems to work for empty file and empty directory.
The code is based on https://github.com/bjorn3/browser_wasi_shim/pull/42/files#diff-177a21b9f40c72ea679cf8658d14ed0d9702afcea694e92e0936f11ab182d2a3R331-R333
with some additional checks.

Challenges

• Fails on a directory that is not empty. In Golang with https://pkg.go.dev/os#RemoveAll it uses a recursive algorithm with unlinkat to unlink the files and remove the empty directories. This goes into an infinite loop.
• The WASI spec requires that we check file and directory permissions/rights before removing/unlinking but the rights base isn't stored anywhere? We couldn't find many examples of checking rights

  browser_wasi_shim/src/wasi_defs.ts

  Line 116 in 7349f7d

  export const RIGHTS_PATH_UNLINK_FILE = 1 << 26;

  
  other than

  browser_wasi_shim/src/fs_fd.ts

  Lines 290 to 291 in 7349f7d

  	(fs_rights_base & BigInt(wasi.RIGHTS_FD_WRITE)) ==
  	BigInt(wasi.RIGHTS_FD_WRITE)

[bjorn3]

The WASI spec requires that we check file and directory permissions/rights before removing/unlinking but the rights base isn't stored anywhere?

Correct. Currently we entirely ignore permissions except at the location you mentioned. #42 has an implementation of this, but I need to look further into how exactly wasi's rights system works to check if the implementation is correct.

Fails on a directory that is not empty. In Golang with https://pkg.go.dev/os#RemoveAll it uses a recursive algorithm with unlinkat to unlink the files and remove the empty directories. This goes into an infinite loop.

Weird.

[HarikrishnanBalagopal]

https://github.com/bjorn3/browser_wasi_shim/pull/50/files#diff-177a21b9f40c72ea679cf8658d14ed0d9702afcea694e92e0936f11ab182d2a3R381
This is the code we have so far

[bjorn3]

I will take a look tomorrow.