command-not-found: rewrite in Rust

nixos/modules/programs/command-not-found/command-not-found.nix

@@ -9,17 +9,9 @@ with lib;
 
 let
   cfg = config.programs.command-not-found;
-  commandNotFound = pkgs.substituteAll {
-    name = "command-not-found";
-    dir = "bin";
-    src = ./command-not-found.pl;
-    isExecutable = true;
-    inherit (pkgs) perl;
+  commandNotFound = pkgs.callPackage ./. {
     inherit (cfg) dbPath;
-    perlFlags = concatStrings (map (path: "-I ${path}/${pkgs.perl.libPrefix} ")
-      [ pkgs.perlPackages.DBI pkgs.perlPackages.DBDSQLite pkgs.perlPackages.StringShellQuote ]);
   };
-
 in
 
 {
@@ -91,5 +83,4 @@ in
 
     environment.systemPackages = [ commandNotFound ];
   };
-
 }

nixos/modules/programs/command-not-found/default.nix

@@ -0,0 +1,18 @@
+{ stdenv, rustPlatform, pkg-config, sqlite
+, dbPath ? "/nix/var/nix/profiles/per-user/root/channels/nixos/programs.sqlite" }:
+
+rustPlatform.buildRustPackage {
+  name = "command-not-found";
+  src = ./rust;
+
+  DB_PATH = dbPath;
+  NIX_SYSTEM = stdenv.system;
+
+  postInstall = ''
+    strip $out/bin/command-not-found
+  '';
+
+  buildInputs = [ sqlite ];
+  nativeBuildInputs = [ pkg-config ];
+  cargoSha256 = "13q61bb4b1q40g424pbssyp3ln79q1a33vmyz9s9wlqnac34cibd";
+}

nixos/modules/programs/command-not-found/rust/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "command-not-found"
+version = "0.1.0"
+edition = "2018"
+
+[dependencies]
+rusqlite = "0.*.*"
+
+[profile.release]
+lto = true

nixos/modules/programs/command-not-found/rust/src/main.rs

@@ -0,0 +1,52 @@
+use rusqlite::{params, Connection, Result};
+use std::env;
+use std::process::exit;
+
+const NIX_SYSTEM: &str = env!("NIX_SYSTEM");
+const DB_PATH: &str = env!("DB_PATH");
+
+fn query_packages(system: &str, program: &str) -> Result<Vec<String>> {
+    Connection::open(DB_PATH)?
+        .prepare("select package from Programs where system = ? and name = ?;")?
+        .query_map(params![system, program], |row| row.get("package"))?
+        .collect::<Result<Vec<String>>>()
+}
+
+fn run_app() -> i32 {
+    let args: Vec<_> = env::args().collect();
+    if args.len() < 2 {
+        eprintln!("USAGE: {} PROGRAMNAME", args[0]);
+        return 1;
+    }
+    let program = &args[1];
+    let system = env::var("NIX_SYSTEM").unwrap_or_else(|_| NIX_SYSTEM.to_string());
+    let packages = match query_packages(&system, program) {
+        Ok(packages) => packages,
+        Err(err) => {
+            eprintln!("Failed to query package database: {}", err);
+            return 1;
+        }
+    };
+    if packages.is_empty() {
+        eprintln!("{}: command not found", program);
+    } else {
+        let advice = if packages.len() > 1 {
+            "It is provided by several packages. You can install it by typing one of the following commands:"
+        } else {
+            "You can install it by typing:"
+        };
+        eprintln!(
+            "The program '{}' is currently not installed. {}",
+            program, advice
+        );
+        for pkg in packages {
+            eprintln!("  nix-env -iA nixos.{}", pkg);
+        }
+    }
+
+    127
+}
+
+fn main() {
+    exit(run_app());
+}