From 6439e899ba438e9b16ee99d754b02ef720bdae96 Mon Sep 17 00:00:00 2001
From: Denis Cornehl <denis@cornehl.org>
Date: Sun, 5 Mar 2023 17:55:12 +0100
Subject: [PATCH] make parallelisation optional

---
 src/justfile.rs | 18 +++++++++---------
 src/parallel.rs | 13 ++++++++++---
 2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/src/justfile.rs b/src/justfile.rs
index c698f4704d..501134821e 100644
--- a/src/justfile.rs
+++ b/src/justfile.rs
@@ -255,13 +255,13 @@ impl<'src> Justfile<'src> {
     };
 
     // let mut ran = BTreeSet::new();
-    parallel::task_scope(|scope| {
+    parallel::task_scope(config.parallel, |scope| {
       for (recipe, arguments) in grouped {
-        scope.spawn(|| {
+        scope.run(|| {
           Self::run_recipe(
             &context, recipe, arguments, &dotenv, search, /*&mut ran*/
           )
-        });
+        })?;
       }
       Ok(())
     })?;
@@ -313,14 +313,14 @@ impl<'src> Justfile<'src> {
     let mut evaluator =
       Evaluator::recipe_evaluator(context.config, dotenv, &scope, context.settings, search);
 
-    parallel::task_scope(|scope| {
+    parallel::task_scope(context.config.parallel, |scope| {
       for Dependency { recipe, arguments } in recipe.dependencies.iter().take(recipe.priors) {
         let arguments = arguments
           .iter()
           .map(|argument| evaluator.evaluate_expression(argument))
           .collect::<RunResult<Vec<String>>>()?;
 
-        scope.spawn(move || {
+        scope.run(move || {
           Self::run_recipe(
             context,
             recipe,
@@ -329,7 +329,7 @@ impl<'src> Justfile<'src> {
             search,
             // ran,
           )
-        });
+        })?;
       }
       Ok(())
     })?;
@@ -339,7 +339,7 @@ impl<'src> Justfile<'src> {
     {
       // let mut ran = BTreeSet::new();
 
-      parallel::task_scope(|scope| {
+      parallel::task_scope(context.config.parallel, |scope| {
         for Dependency { recipe, arguments } in recipe.dependencies.iter().skip(recipe.priors) {
           let mut evaluated = Vec::new();
 
@@ -351,7 +351,7 @@ impl<'src> Justfile<'src> {
             );
           }
 
-          scope.spawn(move || {
+          scope.run(move || {
             Self::run_recipe(
               context,
               recipe,
@@ -360,7 +360,7 @@ impl<'src> Justfile<'src> {
               search,
               // &mut ran,
             )
-          });
+          })?;
         }
         Ok(())
       })?;
diff --git a/src/parallel.rs b/src/parallel.rs
index fffd612849..d38990e8c7 100644
--- a/src/parallel.rs
+++ b/src/parallel.rs
@@ -6,16 +6,22 @@ type ScopeResult<'src> = RunResult<'src, ()>;
 pub(crate) struct TaskScope<'env, 'src, 'inner_scope> {
   inner: &'inner_scope thread::Scope<'env>,
   join_handles: Vec<thread::ScopedJoinHandle<'inner_scope, ScopeResult<'src>>>,
+  parallel: bool,
 }
 
 impl<'env, 'src, 'inner_scope> TaskScope<'env, 'src, 'inner_scope> {
-  pub(crate) fn spawn<'scope, F>(&'scope mut self, f: F)
+  pub(crate) fn run<'scope, F>(&'scope mut self, f: F) -> ScopeResult<'src>
   where
     'src: 'env,
     F: FnOnce() -> ScopeResult<'src>,
     F: Send + 'env,
   {
-    self.join_handles.push(self.inner.spawn(|_scope| f()));
+    if self.parallel {
+      self.join_handles.push(self.inner.spawn(|_scope| f()));
+      Ok(())
+    } else {
+      f()
+    }
   }
 }
 
@@ -25,12 +31,13 @@ impl<'env, 'src, 'inner_scope> TaskScope<'env, 'src, 'inner_scope> {
 /// run. The first error will be returned as result of this `task_scope`.
 ///
 /// Only works for tasks with an `RunResult<'src, ()>` result type.
-pub(crate) fn task_scope<'env, 'src, F>(f: F) -> ScopeResult<'src>
+pub(crate) fn task_scope<'env, 'src, F>(parallel: bool, f: F) -> ScopeResult<'src>
 where
   F: for<'inner_scope> FnOnce(&mut TaskScope<'env, 'src, 'inner_scope>) -> ScopeResult<'src>,
 {
   thread::scope(|scope| {
     let mut task_scope = TaskScope {
+      parallel,
       inner: scope,
       join_handles: Vec::new(),
     };