perf(linter/plugins): remove Arcs (#15431)

Remove 2 levels of `Arc`s from `ExternalLinter`.

1. Make wrapped callback functions `Box<dyn Fn>` instead of `Arc<dyn Fn>`.
2. Avoid wrapping `ThreadsafeFunction`s in `Arc`. The closures take ownership of them anyway. In `wrap_load_plugin`, make the inner closure borrow the `ThreadsafeFunction` from the outer closure.

The first of these (and possibly the 2nd too) was prevented previously by `#[derive(Clone)]` on `Linter`. `Linter` doesn't appear to need to be cloned, so remove that derive.

Author: overlookmotel

apps/oxlint/src/js_plugins/external_linter.rs

@@ -1,4 +1,4 @@
-use std::sync::{Arc, atomic::Ordering, mpsc::channel};
+use std::sync::{atomic::Ordering, mpsc::channel};
 
 use napi::{
     Status,
@@ -36,10 +36,9 @@ pub fn create_external_linter(
 ///
 /// The returned function will panic if called outside of a Tokio runtime.
 fn wrap_load_plugin(cb: JsLoadPluginCb) -> ExternalLinterLoadPluginCb {
-    let cb = Arc::new(cb);
-    Arc::new(move |plugin_path, package_name| {
-        let cb = Arc::clone(&cb);
-        tokio::task::block_in_place(move || {
+    Box::new(move |plugin_path, package_name| {
+        let cb = &cb;
+        tokio::task::block_in_place(|| {
             tokio::runtime::Handle::current().block_on(async move {
                 let result = cb
                     .call_async(FnArgs::from((plugin_path, package_name)))
@@ -70,14 +69,11 @@ pub enum LintFileReturnValue {
 /// Use an `mpsc::channel` to wait for the result from JS side, and block current thread until `lintFile`
 /// completes execution.
 fn wrap_lint_file(cb: JsLintFileCb) -> ExternalLinterLintFileCb {
-    let cb = Arc::new(cb);
-    Arc::new(
+    Box::new(
         move |file_path: String,
               rule_ids: Vec<u32>,
               settings_json: String,
               allocator: &Allocator| {
-            let cb = Arc::clone(&cb);
-
             let (tx, rx) = channel();
 
             // SAFETY: This function is only called when an `ExternalLinter` exists.

crates/oxc_linter/src/external_linter.rs

@@ -1,10 +1,10 @@
-use std::{fmt::Debug, sync::Arc};
+use std::fmt::Debug;
 
 use serde::Deserialize;
 
 use oxc_allocator::Allocator;
 
-pub type ExternalLinterLoadPluginCb = Arc<
+pub type ExternalLinterLoadPluginCb = Box<
     dyn Fn(
             String,
             Option<String>,
@@ -13,7 +13,7 @@ pub type ExternalLinterLoadPluginCb = Arc<
         + Sync,
 >;
 
-pub type ExternalLinterLintFileCb = Arc<
+pub type ExternalLinterLintFileCb = Box<
     dyn Fn(String, Vec<u32>, String, &Allocator) -> Result<Vec<LintFileResult>, String>
         + Sync
         + Send,
@@ -47,7 +47,6 @@ pub struct JsFix {
     pub text: String,
 }
 
-#[derive(Clone)]
 pub struct ExternalLinter {
     pub(crate) load_plugin: ExternalLinterLoadPluginCb,
     pub(crate) lint_file: ExternalLinterLintFileCb,

crates/oxc_linter/src/lib.rs

@@ -94,7 +94,7 @@ fn size_asserts() {
     assert_eq!(size_of::<RuleEnum>(), 16);
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug)]
 #[expect(clippy::struct_field_names)]
 pub struct Linter {
     options: LintOptions,