nix-darwin flake中homeDirectory未定义错误排查求助

在Mac M1上配置nix-darwin与home-manager时，使用以下最小flake配置：

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
    nix-darwin.url = "github:nix-darwin/nix-darwin/master";
    nix-darwin.inputs.nixpkgs.follows = "nixpkgs";
    home-manager.url = "github:nix-community/home-manager";

    # Optional: align inputs to avoid mismatched versions
    home-manager.inputs.nixpkgs.follows = "nixpkgs";
  };

  outputs = inputs@{ self, nix-darwin, nixpkgs, home-manager }:
  let
    configuration = { pkgs, ... }: {
      # List packages installed in system profile. To search by name, run:
      # $ nix-env -qaP | grep wget
      environment.systemPackages =
        [
          pkgs.neovim
          pkgs.git
          pkgs.fzf
          pkgs.tig
          pkgs.zsh
          pkgs.zsh-autosuggestions
          pkgs.zsh-syntax-highlighting
          pkgs.oh-my-zsh
        ];

      # Necessary for using flakes on this system.
      nix.settings.experimental-features = "nix-command flakes";

      # Enable alternative shell support in nix-darwin.
      # programs.fish.enable = true;

      # Set Git commit hash for darwin-version.
      system.configurationRevision = self.rev or self.dirtyRev or null;

      # Used for backwards compatibility, please read the changelog before changing.
      # $ darwin-rebuild changelog
      system.stateVersion = 6;

      # The platform the configuration will be used on.
      nixpkgs.hostPlatform = "aarch64-darwin";
    };
  in
  {
    darwinConfigurations."fes300s-MacBook-Pro" = nix-darwin.lib.darwinSystem {
      modules = [
        configuration
        home-manager.darwinModules.home-manager
        {
                home-manager = {
                        useGlobalPkgs = true;
                        useUserPackages = true;
                        users.fes300 = {
                                home.username = "fes300";
                                home.homeDirectory = "/Users/fes300";
                                home.packages = with nixpkgs.legacyPackages.aarch64-darwin; [
                                        htop
                                ];
                                home.stateVersion = "23.11";
                        };
                };
        }
      ];
    };
  };

执行sudo darwin-rebuild switch时出现错误：

error:
       … while evaluating the attribute 'optionalValue.value'
         at /nix/store/xrr233zsz756b4srmma8z6y0ff606qd4-source/lib/modules.nix:1148:5:
         1147|
         1148|     optionalValue = if isDefined then { value = mergedValue; } else { };
             |     ^
         1149|   };
        … while evaluating a branch condition
         at /nix/store/xrr233zsz756b4srmma8z6y0ff606qd4-source/lib/modules.nix:1148:21:
         1147|
         1148|     optionalValue = if isDefined then { value = mergedValue; } else { };
             |                     ^
         1149|   };
        … while evaluating definitions from `/nix/store/y4570srvp978bdplsk93xsva5x19cf8r-source/modules/system':
        … while evaluating the option `home-manager.users.fes300.home.homeDirectory':
        (stack trace truncated; use '--show-trace' to show the full, detailed trace)
        error: A definition for option `home-manager.users.fes300.home.homeDirectory' is not of type `absolute path'. Definition values:
       - In `/nix/store/6lk47wqmxqg5fs5prvi2i1pazwlkgncj-source/nixos/common.nix': null

问题原因 #

错误根源在于home-manager用户配置的层级结构错误：你把username、homeDirectory等属性嵌套在了home子节点下，但这些属性应该直接定义在用户节点的顶层。这种错误结构导致home-manager无法正确读取homeDirectory的值，最终解析为null，触发类型校验错误。

解决方法 #

修正flake配置中home-manager用户部分的结构，将home.username、home.homeDirectory移到用户节点顶层，同时简化home.packages的写法（因为启用了useGlobalPkgs，可以直接使用全局的pkgs）。

修正后的完整配置：

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
    nix-darwin.url = "github:nix-darwin/nix-darwin/master";
    nix-darwin.inputs.nixpkgs.follows = "nixpkgs";
    home-manager.url = "github:nix-community/home-manager";

    # Optional: align inputs to avoid mismatched versions
    home-manager.inputs.nixpkgs.follows = "nixpkgs";
  };

  outputs = inputs@{ self, nix-darwin, nixpkgs, home-manager }:
  let
    configuration = { pkgs, ... }: {
      environment.systemPackages =
        [
          pkgs.neovim
          pkgs.git
          pkgs.fzf
          pkgs.tig
          pkgs.zsh
          pkgs.zsh-autosuggestions
          pkgs.zsh-syntax-highlighting
          pkgs.oh-my-zsh
        ];

      nix.settings.experimental-features = "nix-command flakes";

      system.configurationRevision = self.rev or self.dirtyRev or null;
      system.stateVersion = 6;
      nixpkgs.hostPlatform = "aarch64-darwin";
    };
  in
  {
    darwinConfigurations."fes300s-MacBook-Pro" = nix-darwin.lib.darwinSystem {
      modules = [
        configuration
        home-manager.darwinModules.home-manager
        {
          home-manager = {
            useGlobalPkgs = true;
            useUserPackages = true;
            users.fes300 = {
              # 将属性移到用户节点顶层
              username = "fes300";
              homeDirectory = "/Users/fes300";
              # 直接使用全局pkgs，无需指定legacyPackages
              packages = with pkgs; [ htop ];
              stateVersion = "23.11";
            };
          };
        }
      ];
    };
  };

重新执行sudo darwin-rebuild switch即可完成配置。

内容的提问来源于stack exchange，提问作者federico sordillo