make

fn make(step: *Step, make_options: Step.MakeOptions) !void {
    // This step completes so quickly that no progress reporting is necessary.
    _ = make_options;

    const b = step.owner;
    const options: *Options = @fieldParentPtr("step", step);

    for (options.args.items) |item| {
        options.addOption(
            []const u8,
            item.name,
            item.path.getPath2(b, step),
        );
    }
    if (!step.inputs.populated()) for (options.args.items) |item| {
        try step.addWatchInput(item.path);
    };

    const basename = "options.zig";

    // Hash contents to file name.
    var hash = b.graph.cache.hash;
    // Random bytes to make unique. Refresh this with new random bytes when
    // implementation is modified in a non-backwards-compatible way.
    hash.add(@as(u32, 0xad95e922));
    hash.addBytes(options.contents.items);
    const sub_path = "c" ++ fs.path.sep_str ++ hash.final() ++ fs.path.sep_str ++ basename;

    options.generated_file.path = try b.cache_root.join(b.allocator, &.{sub_path});

    // Optimize for the hot path. Stat the file, and if it already exists,
    // cache hit.
    if (b.cache_root.handle.access(sub_path, .{})) |_| {
        // This is the hot path, success.
        step.result_cached = true;
        return;
    } else |outer_err| switch (outer_err) {
        error.FileNotFound => {
            const sub_dirname = fs.path.dirname(sub_path).?;
            b.cache_root.handle.makePath(sub_dirname) catch |e| {
                return step.fail("unable to make path '{f}{s}': {s}", .{
                    b.cache_root, sub_dirname, @errorName(e),
                });
            };

            const rand_int = std.crypto.random.int(u64);
            const tmp_sub_path = "tmp" ++ fs.path.sep_str ++
                std.fmt.hex(rand_int) ++ fs.path.sep_str ++
                basename;
            const tmp_sub_path_dirname = fs.path.dirname(tmp_sub_path).?;

            b.cache_root.handle.makePath(tmp_sub_path_dirname) catch |err| {
                return step.fail("unable to make temporary directory '{f}{s}': {s}", .{
                    b.cache_root, tmp_sub_path_dirname, @errorName(err),
                });
            };

            b.cache_root.handle.writeFile(.{ .sub_path = tmp_sub_path, .data = options.contents.items }) catch |err| {
                return step.fail("unable to write options to '{f}{s}': {s}", .{
                    b.cache_root, tmp_sub_path, @errorName(err),
                });
            };

            b.cache_root.handle.rename(tmp_sub_path, sub_path) catch |err| switch (err) {
                error.PathAlreadyExists => {
                    // Other process beat us to it. Clean up the temp file.
                    b.cache_root.handle.deleteFile(tmp_sub_path) catch |e| {
                        try step.addError("warning: unable to delete temp file '{f}{s}': {s}", .{
                            b.cache_root, tmp_sub_path, @errorName(e),
                        });
                    };
                    step.result_cached = true;
                    return;
                },
                else => {
                    return step.fail("unable to rename options from '{f}{s}' to '{f}{s}': {s}", .{
                        b.cache_root,    tmp_sub_path,
                        b.cache_root,    sub_path,
                        @errorName(err),
                    });
                },
            };
        },
        else => |e| return step.fail("unable to access options file '{f}{s}': {s}", .{
            b.cache_root, sub_path, @errorName(e),
        }),
    }
}