openUnresolved

    pub fn openUnresolved(
        arena: Allocator,
        io: Io,
        cwd: []const u8,
        unresolved_path: []const u8,
        thing: enum { @"zig lib", @"global cache", @"local cache", @"build root" },
    ) Cache.Directory {
        const path = resolvePath(arena, cwd, &.{unresolved_path}) catch |err| {
            fatal("unable to resolve {t} directory: {t}", .{ thing, err });
        };
        const nonempty_path = if (path.len == 0) "." else path;
        const handle_or_err = switch (thing) {
            .@"zig lib", .@"build root" => Dir.cwd().openDir(io, nonempty_path, .{}),
            .@"global cache", .@"local cache" => Dir.cwd().createDirPathOpen(io, nonempty_path, .{}),
        };
        return .{
            .path = if (path.len == 0) null else path,
            .handle = handle_or_err catch |err| {
                const extra_str: []const u8 = e: {
                    if (thing == .@"global cache") switch (err) {
                        error.AccessDenied, error.ReadOnlyFileSystem => break :e "\n" ++
                            "If this location is not writable then consider specifying an alternative with " ++
                            "the ZIG_GLOBAL_CACHE_DIR environment variable or the --global-cache-dir option.",
                        else => {},
                    };
                    break :e "";
                };
                fatal("unable to open {t} directory {q}: {t}{s}", .{ thing, nonempty_path, err, extra_str });
            },
        };
    }