feat(step): nix-helper

Cargo.toml

@@ -54,6 +54,7 @@ notify-rust = "~4.11"
 wildmatch = "2.3.0"
 rust-i18n = "3.0.1"
 sys-locale = "0.3.1"
+whoami = "1.5.2"
 
 [package.metadata.generate-rpm]
 assets = [{ source = "target/release/topgrade", dest = "/usr/bin/topgrade" }]

locales/app.yml

@@ -793,3 +793,21 @@ _version: 2
   es: "No se pueden actualizar las aplicaciones de Microsoft Store, se requiere intervención manual"
   fr: "Impossible de mettre à jour les applications du Microsoft Store, une intervention manuelle est nécessaire"
   zh_TW: "無法更新 Microsoft Store 應用，需手動幹預"
+
+"No flake configurations found for nh":
+  en: "No flake configurations found for nh"
+  es: "No se encontraron configuraciones de flake para nh."
+  fr: "Aucune configuration de flake trouvée pour nh."
+  zh_TW: "没有为 nh 找到 flake 配置"
+
+"No username found":
+  en: "No username found"
+  es: "No se encontró ningún nombre de usuario."
+  fr: "Aucun nom d'utilisateur trouvé."
+  zh_TW: "未找到用户名"
+
+"No hostname found":
+  en: "No hostname found"
+  es: "No se encontró ningún nombre de host."
+  fr: "Aucun nom d'hôte trouvé."
+  zh_TW: "未找到主机名"

src/config.rs

@@ -115,6 +115,7 @@ pub enum Step {
     Mise,
     Myrepos,
     Nix,
+    NixHelper,
     Node,
     Opam,
     Pacdef,

src/main.rs

@@ -311,6 +311,7 @@ fn run() -> Result<()> {
         runner.execute(Step::Yadm, "yadm", || unix::run_yadm(&ctx))?;
         runner.execute(Step::Nix, "nix", || unix::run_nix(&ctx))?;
         runner.execute(Step::Nix, "nix upgrade-nix", || unix::run_nix_self_upgrade(&ctx))?;
+        runner.execute(Step::NixHelper, "nh", || unix::run_nix_helper(&ctx))?;
         runner.execute(Step::Guix, "guix", || unix::run_guix(&ctx))?;
         runner.execute(Step::HomeManager, "home-manager", || unix::run_home_manager(&ctx))?;
         runner.execute(Step::Asdf, "asdf", || unix::run_asdf(&ctx))?;

src/steps/os/unix.rs

@@ -20,6 +20,8 @@ use regex::Regex;
 use rust_i18n::t;
 use semver::Version;
 use tracing::debug;
+use whoami::fallible::hostname;
+use whoami::fallible::username;
 
 #[cfg(target_os = "linux")]
 use super::linux::Distribution;
@@ -620,8 +622,82 @@ fn nix_profile_dir(nix: &Path) -> Result<Option<PathBuf>> {
     )
 }
 
+/// Update NixOS and home-manager through a flake using `nh`
+///
+/// See: https://github.com/viperML/nh
+pub fn run_nix_helper(ctx: &ExecutionContext) -> Result<()> {
+    let nix = require("nix")?;
+    let nix_helper = require("nh")?;
+    let flake_path: PathBuf = std::env::var_os("FLAKE")
+        .ok_or_else(|| SkipStep("$FLAKE not set".into()))?
+        .require()?
+        .into();
+
+    flake_path.join("flake.nix").require()?;
+
+    let run_type = ctx.run_type();
+
+    // we never dry run this because it doesn't perform any changes and because it ensures that the
+    // behaviour between dry and wet runs is the same i.e. the checks performed are the same
+    // between dry and wet runs
+    let run_nix_eval = |attr| -> Result<String> {
+        Ok(String::from_utf8(
+            std::process::Command::new(&nix)
+                .args(nix_args())
+                .arg("eval")
+                .arg(format!("{}#{attr}", flake_path.display()))
+                .arg("--apply")
+                .arg("builtins.attrNames")
+                .output_checked()?
+                .stdout,
+        )?)
+    };
+
+    let nixos_cfg = run_nix_eval("nixosConfigurations");
+    let home_cfg = run_nix_eval("homeConfigurations");
+
+    if nixos_cfg.as_ref().or(home_cfg.as_ref()).is_err() && !run_type.dry() {
+        return Err(SkipStep(t!("No flake configurations found for nh").to_string()).into());
+    }
+
+    print_separator("nh flake");
+    run_type
+        .execute(&nix)
+        .args(nix_args())
+        .arg("flake")
+        .arg("update")
+        .arg("--flake")
+        .arg(&flake_path)
+        .status_checked()?;
+
+    let username = username().wrap_err_with(|| t!("No username found").to_string())?;
+    let hostname = hostname().wrap_err_with(|| t!("No hostname found").to_string())?;
+
+    // Let's not do any JSON parsing and just Keep It Simple
+    if nixos_cfg.is_ok_and(|x| x.contains(&format!(r#""{hostname}""#))) {
+        print_separator("nh os");
+
+        run_type.execute(&nix_helper).arg("os").arg("switch").status_checked()?;
+    }
+
+    if let Ok(home_cfg) = home_cfg {
+        let username_at_hostname = format!(r#""{username}@{hostname}""#);
+        if home_cfg.contains(&format!(r#""{username}""#)) || home_cfg.contains(&username_at_hostname) {
+            print_separator("nh home");
+
+            run_type
+                .execute(&nix_helper)
+                .arg("home")
+                .arg("switch")
+                .status_checked()?;
+        }
+    }
+
+    Ok(())
+}
+
 fn nix_args() -> [&'static str; 2] {
-    ["--extra-experimental-features", "nix-command"]
+    ["--extra-experimental-features", "nix-command flakes"]
 }
 
 pub fn run_yadm(ctx: &ExecutionContext) -> Result<()> {