Convenience script for switching specialisations Since Home Manager's specialisation feature is experimental and UX is nearly non-existent, this kind of helper program is essential.

Changes

5 changed files (+138/-0)

• README.md
  • @@ -40,6 +40,20 @@
    - [`sway`](https://archlinux.org/packages/extra/x86_64/sway/) ... The one installed using Nix does not launch. - [`pantheon-polkit-agent`](https://archlinux.org/packages/extra/x86_64/pantheon-polkit-agent/) ... The one installed installed using Nix cannot lookup `polkit-agent-helper-1`. + ## Programs + + ### `specialisation` + + `specialisation` activates the given Home Manager specialisation. + + ```sh + # Switch to dark mode + specialisation dark + + # Switch to light mode + specialisation light + ``` + ## License [Apache-2.0](./LICENSE)
• flake.nix
  • @@ -49,6 +49,12 @@ themes.catppuccin.flavor = "latte";
    }; }; + home.packages = [ + (import ./programs/specialise { + inherit pkgs; + }) + ]; + features = nixpkgs.lib.mkDefault { identity = { name = "Shota FUJI";
• programs/specialise/default.nix (new)
  • @@ -0,0 +1,12 @@
    + { pkgs }: + pkgs.buildGoModule { + name = "specialise"; + + src = ./.; + + vendorHash = null; + + ldflags = [ + "-X main.homeManagerPath=${pkgs.home-manager}/bin/home-manager" + ]; + }
• programs/specialise/go.mod (new)
  • @@ -0,0 +1,3 @@
    + module github.com/pocka/system/programs/specialise + + go 1.21.5
• programs/specialise/specialise.go (new)
  • @@ -0,0 +1,103 @@
    + package main + + import ( + "flag" + "fmt" + "log" + "os" + "os/exec" + "strings" + ) + + var homeManagerPath = "home-manager" + + func main() { + flag.Parse() + + args := flag.Args() + + switch len(args) { + case 0: + log.Fatal("Argument not set: which specialisation to switch to?") + case 1: + break + default: + log.Fatalf("specialisation takes exactly 1 argument: You set %d arguments", len(args)) + } + + target := args[0] + + if strings.Contains(target, "/") { + log.Fatalf("specialisation cannot have slash (\"/\"): %s", target) + } + + cmd := exec.Command(homeManagerPath, "generations") + + var out strings.Builder + cmd.Stdout = &out + + if err := cmd.Run(); err != nil { + log.Fatal(err) + } + + paths := parseGenerationsOutput(out.String()) + + for _, path := range paths { + dir := os.DirFS(path) + + exe, err := dir.Open(fmt.Sprintf("specialisation/%s/activate", target)) + if err != nil { + continue + } + defer exe.Close() + + // Whether `fs.FS.Open` performs actual FS open operation is undocumented. + // Make sure the file exists by getting file stats. + if _, err := exe.Stat(); err != nil { + // Home Manager's specialisation feature has fundamental design failure: + // there is no way to go back to "unspecialised" generation or switch to another + // specialisations once activated a specialisation. Because of this, I have to + // brute-force each Home Manager generation directories. + // https://github.com/nix-community/home-manager/issues/4073 + continue + } + + bin := fmt.Sprintf("%s/specialisation/%s/activate", path, target) + + log.Printf("> %s", bin) + cmd := exec.Command(bin) + + if err := cmd.Run(); err != nil { + log.Fatal(err) + } + + log.Printf("Activated %s", target) + os.Exit(0) + } + + log.Fatalf("No specialisation named \"%s\" found", target) + } + + // parseGenerationsOutput parses stdout of `home-manager generations` and + // returns the list of paths to generation directories. + func parseGenerationsOutput(stdout string) []string { + lines := strings.Split(stdout, "\n") + + paths := make([]string, 0, len(lines)) + + for _, line := range strings.Split(stdout, "\n") { + tokens := strings.Split(line, " ") + if len(tokens) == 0 { + continue + } + + last := tokens[len(tokens)-1] + if !strings.HasPrefix(last, "/") { + continue + } + + paths = append(paths, last) + } + + return paths + }