Create new type LazyJobserverClient

and use it to replace `jobserver::Client`.

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

src/binstall/install.rs

@@ -12,7 +12,7 @@ pub async fn install(
     resolution: Resolution,
     opts: Arc<Options>,
     desired_targets: DesiredTargets,
-    jobserver_client: jobserver::Client,
+    jobserver_client: LazyJobserverClient,
 ) -> Result<()> {
     match resolution {
         Resolution::Fetch {
@@ -140,8 +140,10 @@ async fn install_from_package(
 async fn install_from_source(
     package: Package<Meta>,
     target: &str,
-    jobserver_client: jobserver::Client,
+    lazy_jobserver_client: LazyJobserverClient,
 ) -> Result<()> {
+    let jobserver_client = lazy_jobserver_client.get().await?;
+
     debug!(
         "Running `cargo install {} --version {} --target {target}`",
         package.name, package.version

src/helpers/jobserver_client.rs

@@ -1,20 +1,35 @@
 use std::num::NonZeroUsize;
+use std::sync::Arc;
 use std::thread::available_parallelism;
 
+use jobserver::Client;
+use tokio::sync::OnceCell;
+
 use crate::BinstallError;
 
-pub fn create_jobserver_client() -> Result<jobserver::Client, BinstallError> {
-    use jobserver::Client;
+#[derive(Clone)]
+pub struct LazyJobserverClient(Arc<OnceCell<Client>>);
 
-    // Safety:
-    //
-    // Client::from_env is unsafe because from_raw_fd is unsafe.
-    // It doesn't do anything that is actually unsafe, like
-    // dereferencing pointer.
-    if let Some(client) = unsafe { Client::from_env() } {
-        Ok(client)
-    } else {
-        let ncore = available_parallelism().map(NonZeroUsize::get).unwrap_or(1);
-        Ok(Client::new(ncore)?)
+impl LazyJobserverClient {
+    /// This must be called at the start of the program since
+    /// `Client::from_env` requires that.
+    #[allow(clippy::new_without_default)]
+    pub fn new() -> Self {
+        // Safety:
+        //
+        // Client::from_env is unsafe because from_raw_fd is unsafe.
+        // It doesn't do anything that is actually unsafe, like
+        // dereferencing pointer.
+        let opt = unsafe { Client::from_env() };
+        Self(Arc::new(OnceCell::new_with(opt)))
+    }
+
+    pub async fn get(&self) -> Result<&Client, BinstallError> {
+        self.0
+            .get_or_try_init(|| async {
+                let ncore = available_parallelism().map(NonZeroUsize::get).unwrap_or(1);
+                Ok(Client::new(ncore)?)
+            })
+            .await
     }
 }

src/main.rs

@@ -160,10 +160,7 @@ impl Termination for MainExit {
 
 fn main() -> MainExit {
     // Create jobserver client
-    let jobserver_client = match create_jobserver_client() {
-        Ok(jobserver_client) => jobserver_client,
-        Err(binstall_err) => return MainExit::Error(binstall_err),
-    };
+    let jobserver_client = LazyJobserverClient::new();
 
     let start = Instant::now();
 
@@ -184,7 +181,7 @@ fn main() -> MainExit {
     })
 }
 
-async fn entry(jobserver_client: jobserver::Client) -> Result<()> {
+async fn entry(jobserver_client: LazyJobserverClient) -> Result<()> {
     // Filter extraneous arg when invoked by cargo
     // `cargo run -- --help` gives ["target/debug/cargo-binstall", "--help"]
     // `cargo binstall --help` gives ["/home/ryan/.cargo/bin/cargo-binstall", "binstall", "--help"]