lintcheck: use multithreading unless --fix or --recursive is used

Author: samueltardieu

lintcheck/src/config.rs

@@ -3,9 +3,14 @@ use std::path::PathBuf;
 
 #[derive(Clone, Debug, Parser)]
 pub(crate) struct LintcheckConfig {
-    /// Number of threads to use, 0 automatic choice
-    #[clap(long = "jobs", short = 'j', value_name = "N", default_value_t = 1)]
-    pub max_jobs: usize,
+    /// Always defined after the config phase
+    #[clap(
+        long = "jobs",
+        short = 'j',
+        value_name = "N",
+        help = "Number of threads to use (default: all unless --fix or --recursive)"
+    )]
+    pub max_jobs: Option<usize>,
     /// Set the path for a crates.toml where lintcheck should read the sources from
     #[clap(
         long = "crates-toml",
@@ -50,9 +55,12 @@ impl LintcheckConfig {
         ));
 
         // look at the --threads arg, if 0 is passed, use the threads count
-        if config.max_jobs == 0 {
-            // automatic choice
-            config.max_jobs = std::thread::available_parallelism().map_or(1, |n| n.get());
+        if config.max_jobs.is_none() {
+            config.max_jobs = Some(if config.fix || config.recursive {
+                1
+            } else {
+                std::thread::available_parallelism().map_or(1, |n| n.get())
+            });
         };
 
         for lint_name in &mut config.lint_filter {

lintcheck/src/main.rs

@@ -317,10 +317,10 @@ impl Crate {
         // advance the atomic index by one
         let index = target_dir_index.fetch_add(1, Ordering::SeqCst);
         // "loop" the index within 0..thread_limit
-        let thread_index = index % config.max_jobs;
+        let thread_index = index % config.max_jobs.unwrap();
         let perc = (index * 100) / total_crates_to_lint;
 
-        if config.max_jobs == 1 {
+        if config.max_jobs.unwrap() == 1 {
             println!(
                 "{index}/{total_crates_to_lint} {perc}% Linting {} {}",
                 &self.name, &self.version
@@ -627,7 +627,7 @@ fn main() {
     // order to achieve some kind of parallelism
 
     rayon::ThreadPoolBuilder::new()
-        .num_threads(config.max_jobs)
+        .num_threads(config.max_jobs.unwrap())
         .build_global()
         .unwrap();