dirOpenFileWasi

fn dirOpenFileWasi(
    userdata: ?*anyopaque,
    dir: Dir,
    sub_path: []const u8,
    flags: Dir.OpenFileOptions,
) File.OpenError!File {
    if (builtin.link_libc) return dirOpenFilePosix(userdata, dir, sub_path, flags);
    const t: *Threaded = @ptrCast(@alignCast(userdata));
    const wasi = std.os.wasi;
    var base: std.os.wasi.rights_t = .{};
    // POLL_FD_READWRITE only grants extra rights if the corresponding FD_READ and/or FD_WRITE
    // is also set.
    if (flags.isRead()) {
        base.FD_READ = true;
        base.FD_TELL = true;
        base.FD_SEEK = true;
        base.FD_FILESTAT_GET = true;
        base.POLL_FD_READWRITE = true;
    }
    if (flags.isWrite()) {
        base.FD_WRITE = true;
        base.FD_TELL = true;
        base.FD_SEEK = true;
        base.FD_DATASYNC = true;
        base.FD_FDSTAT_SET_FLAGS = true;
        base.FD_SYNC = true;
        base.FD_ALLOCATE = true;
        base.FD_ADVISE = true;
        base.FD_FILESTAT_SET_TIMES = true;
        base.FD_FILESTAT_SET_SIZE = true;
        base.POLL_FD_READWRITE = true;
    }
    const lookup_flags: wasi.lookupflags_t = .{};
    const oflags: wasi.oflags_t = .{};
    const inheriting: wasi.rights_t = .{};
    const fdflags: wasi.fdflags_t = .{};
    var fd: posix.fd_t = undefined;
    const syscall: Syscall = try .start();
    while (true) {
        switch (wasi.path_open(dir.handle, lookup_flags, sub_path.ptr, sub_path.len, oflags, base, inheriting, fdflags, &fd)) {
            .SUCCESS => {
                syscall.finish();
                break;
            },
            .INTR => {
                try syscall.checkCancel();
                continue;
            },
            else => |e| {
                syscall.finish();
                switch (e) {
                    .FAULT => |err| return errnoBug(err),
                    .BADF => |err| return errnoBug(err), // File descriptor used after closed.
                    .ACCES => return error.AccessDenied,
                    .FBIG => return error.FileTooBig,
                    .OVERFLOW => return error.FileTooBig,
                    .ISDIR => return error.IsDir,
                    .LOOP => return error.SymLinkLoop,
                    .MFILE => return error.ProcessFdQuotaExceeded,
                    .NFILE => return error.SystemFdQuotaExceeded,
                    .NODEV => return error.NoDevice,
                    .NOENT => return error.FileNotFound,
                    .NOMEM => return error.SystemResources,
                    .NOTDIR => return error.NotDir,
                    .PERM => return error.PermissionDenied,
                    .BUSY => return error.DeviceBusy,
                    .NOTCAPABLE => return error.AccessDenied,
                    .NAMETOOLONG => return error.NameTooLong,
                    .INVAL => return error.BadPathName,
                    .ILSEQ => return error.BadPathName,
                    else => |err| return posix.unexpectedErrno(err),
                }
            },
        }
    }
    errdefer closeFd(fd);

    if (!flags.allow_directory) {
        const is_dir = is_dir: {
            const stat = fileStat(t, .{ .handle = fd, .flags = .{ .nonblocking = false } }) catch |err| switch (err) {
                // The directory-ness is either unknown or unknowable
                error.Streaming => break :is_dir false,
                else => |e| return e,
            };
            break :is_dir stat.kind == .directory;
        };
        if (is_dir) return error.IsDir;
    }

    return .{
        .handle = fd,
        .flags = .{ .nonblocking = false },
    };
}