From cc4299b11a7bab262d3e1f87aad582659f4e183c Mon Sep 17 00:00:00 2001
From: Yaroslav Bolyukin <iam@lach.pw>
Date: Thu, 18 Sep 2025 20:10:53 +0000
Subject: [PATCH] refactor: nix-eval is now fully sync, parallelism should be explicit at the callsite


---
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2070,8 +2070,6 @@
  "serde_json",
  "test-log",
  "thiserror 2.0.16",
- "tokio",
- "tokio-util",
  "tracing",
  "tracing-indicatif",
  "vte 0.15.0",
--- a/cmds/fleet/src/cmds/build_systems.rs
+++ b/cmds/fleet/src/cmds/build_systems.rs
@@ -8,7 +8,7 @@
 	opts::FleetOpts,
 };
 use nix_eval::nix_go;
-use tokio::task::LocalSet;
+use tokio::task::{LocalSet, spawn_blocking};
 use tracing::{Instrument, error, field, info, info_span, warn};
 
 #[derive(Parser)]
@@ -34,7 +34,9 @@
 	// let action = Action::from(self.subcommand.clone());
 	let nixos = host.nixos_config().await?;
 	let drv = nix_go!(nixos.system.build[{ build_attr }]);
-	let out_output = drv.build("out").await?;
+	let out_output = spawn_blocking(move || drv.build("out"))
+		.await
+		.expect("system derivation build should not panic")?;
 
 	// We already have system profiles for backups.
 	if !host.local {
--- a/cmds/fleet/src/cmds/secrets/mod.rs
+++ b/cmds/fleet/src/cmds/secrets/mod.rs
@@ -19,7 +19,7 @@
 use owo_colors::OwoColorize;
 use serde::Deserialize;
 use tabled::{Table, Tabled};
-use tokio::fs::read;
+use tokio::{fs::read, task::spawn_blocking};
 use tracing::{Instrument, error, info, info_span, warn};
 
 #[derive(Parser)]
@@ -288,7 +288,9 @@
 
 	let generator = nix_go!(call_package(generator)(Obj {}));
 
-	let generator = generator.build("out").await?;
+	let generator = spawn_blocking(move || generator.build("out"))
+		.await
+		.expect("nix build shouldn't fail")?;
 	let generator = host.remote_derivation(&generator).await?;
 
 	let out_parent = host.mktemp_dir().await?;
--- a/cmds/fleet/src/cmds/tf.rs
+++ b/cmds/fleet/src/cmds/tf.rs
@@ -10,6 +10,7 @@
 use tokio::{
 	fs::{self, create_dir_all},
 	process::Command,
+	task::spawn_blocking,
 };
 use tracing::debug;
 
@@ -38,7 +39,10 @@
 			debug!("generating terraform configs");
 			let system = &config.local_system;
 			let config = &config.config_field;
-			let data: PathBuf = nix_go!(config.tf({ system })).build("out").await?;
+			let data = nix_go!(config.tf({ system }));
+			let data: PathBuf = spawn_blocking(move || data.build("out"))
+				.await
+				.expect("tf.json derivation should not fail")?;
 			let data = fs::read(&data).await?;
 
 			create_dir_all(&dir).await?;
--- a/crates/nix-eval/Cargo.toml
+++ b/crates/nix-eval/Cargo.toml
@@ -11,8 +11,6 @@
 serde = { workspace = true, features = ["derive"] }
 serde_json.workspace = true
 thiserror.workspace = true
-tokio = { workspace = true }
-tokio-util.workspace = true
 tracing.workspace = true
 
 cxx = "1.0.168"
--- a/crates/nix-eval/src/lib.rs
+++ b/crates/nix-eval/src/lib.rs
@@ -750,7 +750,7 @@
 		})?;
 		Ok(out)
 	}
-	pub async fn build(&self, output: &str) -> Result<PathBuf> {
+	pub fn build(&self, output: &str) -> Result<PathBuf> {
 		if !self.is_derivation() {
 			bail!("expected derivation to build")
 		}

-- 
gitstuff