From 5b8611744b844eee3568849910ba6edc0efda7c6 Mon Sep 17 00:00:00 2001
From: i1i1 <vanyarybin1@live.ru>
Date: Thu, 10 Aug 2023 01:47:10 +0300
Subject: [PATCH] Convert eval arguments to type-safe clap derive

---
 src/cli.rs          |  3 +-
 src/command/eval.rs | 95 +++++++++++++++++++++------------------------
 2 files changed, 45 insertions(+), 53 deletions(-)

diff --git a/src/cli.rs b/src/cli.rs
index c6246bd..e424d93 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -191,8 +191,7 @@ It's also possible to specify the preference using environment variables. See <h
                 ),
         );
 
-        // deprecated alias
-        app = app.subcommand(command::eval::deprecated_alias());
+        // TODO: handle deprecated alias
 
         #[cfg(debug_assertions)]
         register_command!(test_progress, app);
diff --git a/src/command/eval.rs b/src/command/eval.rs
index 0667444..b9bfa5d 100644
--- a/src/command/eval.rs
+++ b/src/command/eval.rs
@@ -1,44 +1,39 @@
 use std::path::PathBuf;
 
-use clap::{value_parser, Arg, ArgMatches, Command as ClapCommand, FromArgMatches};
+use clap::{ArgMatches, Args, Command as ClapCommand, FromArgMatches};
 
 use crate::error::ColmenaError;
 use crate::nix::hive::HiveArgs;
 
-pub fn subcommand() -> ClapCommand {
-    subcommand_gen("eval")
-}
-
-pub fn deprecated_alias() -> ClapCommand {
-    subcommand_gen("introspect").hide(true)
-}
-
-fn subcommand_gen(name: &'static str) -> ClapCommand {
-    ClapCommand::new(name)
-        .about("Evaluate an expression using the complete configuration")
-        .long_about(r#"Evaluate an expression using the complete configuration
+#[derive(Debug, Args)]
+#[command(
+    name = "eval",
+    alias = "introspect",
+    about = "Evaluate an expression using the complete configuration",
+    long_about = r#"Evaluate an expression using the complete configuration
 
 Your expression should take an attribute set with keys `pkgs`, `lib` and `nodes` (like a NixOS module) and return a JSON-serializable value.
 
 For example, to retrieve the configuration of one node, you may write something like:
 
     { nodes, ... }: nodes.node-a.config.networking.hostName
-"#)
-        .arg(Arg::new("expression_file")
-            .index(1)
-            .value_name("FILE")
-            .help("The .nix file containing the expression")
-            .num_args(1)
-            .value_parser(value_parser!(PathBuf)))
-        .arg(Arg::new("expression")
-            .short('E')
-            .value_name("EXPRESSION")
-            .help("The Nix expression")
-            .num_args(1))
-        .arg(Arg::new("instantiate")
-            .long("instantiate")
-            .help("Actually instantiate the expression")
-            .num_args(0))
+"#
+)]
+pub struct Opts {
+    #[arg(short = 'E', value_name = "EXPRESSION", help = "The Nix expression")]
+    expression: Option<String>,
+    #[arg(long, help = "Actually instantiate the expression")]
+    instantiate: bool,
+    #[arg(
+        value_name = "FILE",
+        help = "The .nix file containing the expression",
+        conflicts_with("expression")
+    )]
+    expression_file: Option<PathBuf>,
+}
+
+pub fn subcommand() -> ClapCommand {
+    Opts::augment_args(ClapCommand::new("eval"))
 }
 
 pub async fn run(global_args: &ArgMatches, local_args: &ArgMatches) -> Result<(), ColmenaError> {
@@ -54,31 +49,29 @@ pub async fn run(global_args: &ArgMatches, local_args: &ArgMatches) -> Result<()
         .await
         .unwrap();
 
-    if !(local_args.contains_id("expression") ^ local_args.contains_id("expression_file")) {
-        log::error!("Either an expression (-E) or a .nix file containing an expression should be specified, not both.");
-        quit::with_code(1);
-    }
+    let Opts {
+        instantiate,
+        expression,
+        expression_file,
+    } = Opts::from_arg_matches(local_args).expect("Failed to parse args");
 
-    let expression = if local_args.contains_id("expression") {
-        local_args
-            .get_one::<String>("expression")
-            .unwrap()
-            .to_owned()
-    } else {
-        let path = local_args
-            .get_one::<PathBuf>("expression_file")
-            .unwrap()
-            .to_owned();
-        format!(
-            "import {}",
-            path.canonicalize()
-                .expect("Could not generate absolute path to expression file.")
-                .to_str()
-                .unwrap()
-        )
+    let expression = expression_file
+        .map(|path| {
+            format!(
+                "import {}",
+                path.canonicalize()
+                    .expect("Could not generate absolute path to expression file.")
+                    .to_str()
+                    .unwrap()
+            )
+        })
+        .or(expression);
+
+    let Some(expression) = expression else {
+        log::error!("Provide either an expression (-E) or a .nix file containing an expression.");
+        quit::with_code(1);
     };
 
-    let instantiate = local_args.get_flag("instantiate");
     let result = hive.introspect(expression, instantiate).await?;
 
     if instantiate {