fix: __check-config runs quietly without a home directory

nix/checks.ulu.nix

@@ -67,6 +67,11 @@
           pkgs.runCommand "valw-home-module" { } ''
             grep -qx 'timeout_secs = 3' ${set.xdg.configFile."valw/config.toml".source}
             grep -qx 'volume = 0.4' ${set.xdg.configFile."valw/config.toml".source}
+            # Quiet, and no home directory needed.
+            HOME=/nonexistent ${valw}/bin/valw __check-config ${
+              set.xdg.configFile."valw/config.toml".source
+            } 2> err
+            test ! -s err
             touch $out
           '';
 

src/main.rs

@@ -160,6 +160,16 @@ enum Mode {
 
 fn main() -> ExitCode {
     let cli = Cli::parse();
+    // home-manager runs this in the build sandbox: no home, no logs, quiet.
+    if let Command::CheckConfig { file } = &cli.command {
+        return match config::check(file) {
+            Ok(()) => ExitCode::SUCCESS,
+            Err(e) => {
+                eprint!("{}", error::render(&e, None));
+                ExitCode::FAILURE
+            }
+        };
+    }
     let log = log::init(&log::default_dir(), Local::now());
     log::install_panic_hook(log.clone());
     tracing::info!(
@@ -191,6 +201,7 @@ fn run(cli: Cli) -> Result<()> {
         Command::Window { common } => capture(Mode::Window, common),
         Command::Zoom { common } => capture(Mode::Zoom, common),
         Command::Edit { file } => editor::run(&file),
+        // Handled in main, before logging starts.
         Command::CheckConfig { file } => config::check(&file),
         Command::ComboDemo => sound::demo(&config::load(&config::default_path())?.sound),
         Command::Toolbar => {