createChild

fn createChild(
    parent: *Build,
    dep_name: []const u8,
    root: Cache.Path,
    pkg_hash: []const u8,
    pkg_deps: AvailableDeps,
    user_input_options: PackageOptions.Map,
) error{OutOfMemory}!*Build {
    const arena = parent.graph.arena;
    const child = try arena.create(Build);
    child.* = .{
        .graph = parent.graph,
        .root = root,
        .allocator = arena,
        .install_tls = .{
            .step = .init(.{
                .tag = .top_level,
                .name = "install",
                .owner = child,
            }),
            .description = "Copy build artifacts to prefix path",
        },
        .uninstall_tls = .{
            .step = .init(.{
                .tag = .top_level,
                .name = "uninstall",
                .owner = child,
            }),
            .description = "Remove build artifacts from prefix path",
        },
        .user_input_options = user_input_options,
        .invalid_user_input = false,
        .default_step = undefined,
        .top_level_steps = .{},
        .debug_log_scopes = parent.debug_log_scopes,
        .dep_prefix = parent.fmt("{s}{s}.", .{ parent.dep_prefix, dep_name }),
        .modules = .empty,
        .named_writefiles = .empty,
        .named_lazy_paths = .empty,
        .pkg_hash = pkg_hash,
        .available_deps = pkg_deps,
    };
    try child.top_level_steps.put(arena, child.install_tls.step.name, &child.install_tls);
    try child.top_level_steps.put(arena, child.uninstall_tls.step.name, &child.uninstall_tls);
    child.default_step = &child.install_tls.step;
    return child;
}