make dir watcher use std::thread instead of async (FuelLabs#4658)

## Description
This PR changes how we are watching for directory changes in the
language server. Previously we were using tokio, this has now been
changed to use a regular thread and `std::mpsc::channel`. We are about
to move away from an `async` framework in the language server so this is
a small effort towards removing reliance on tokio.

sway-lsp/src/core/session.rs

@@ -20,7 +20,13 @@ use dashmap::DashMap;
 use forc_pkg as pkg;
 use parking_lot::RwLock;
 use pkg::{manifest::ManifestFile, Programs};
-use std::{fs::File, io::Write, path::PathBuf, sync::Arc, vec};
+use std::{
+    fs::File,
+    io::Write,
+    path::PathBuf,
+    sync::{atomic::Ordering, Arc},
+    vec,
+};
 use sway_core::{
     decl_engine::DeclEngine,
     language::{
@@ -99,10 +105,13 @@ impl Session {
     }
 
     pub fn shutdown(&self) {
-        // shutdown the thread watching the manifest file
-        let handle = self.sync.notify_join_handle.read();
-        if let Some(join_handle) = &*handle {
-            join_handle.abort();
+        // Set the should_end flag to true
+        self.sync.should_end.store(true, Ordering::Relaxed);
+
+        // Wait for the thread to finish
+        let mut join_handle_option = self.sync.notify_join_handle.write();
+        if let Some(join_handle) = std::mem::take(&mut *join_handle_option) {
+            let _ = join_handle.join();
         }
 
         // Delete the temporary directory.

sway-lsp/src/core/sync.rs

@@ -12,7 +12,9 @@ use std::{
     fs::{self, File},
     io::{Read, Write},
     path::{Path, PathBuf},
-    sync::Arc,
+    sync::{atomic::AtomicBool, mpsc, Arc},
+    thread::JoinHandle,
+    time::Duration,
 };
 use sway_types::{SourceEngine, Span};
 use tempfile::Builder;
@@ -27,7 +29,9 @@ pub enum Directory {
 #[derive(Debug)]
 pub struct SyncWorkspace {
     pub directories: DashMap<Directory, PathBuf>,
-    pub notify_join_handle: RwLock<Option<tokio::task::JoinHandle<()>>>,
+    pub notify_join_handle: RwLock<Option<JoinHandle<()>>>,
+    // if we should shutdown the thread watching the manifest file
+    pub should_end: Arc<AtomicBool>,
 }
 
 impl SyncWorkspace {
@@ -37,6 +41,7 @@ impl SyncWorkspace {
         Self {
             directories: DashMap::new(),
             notify_join_handle: RwLock::new(None),
+            should_end: Arc::new(AtomicBool::new(false)),
         }
     }
 
@@ -175,13 +180,13 @@ impl SyncWorkspace {
                 if let Some(temp_manifest_path) = self.temp_manifest_path() {
                     edit_manifest_dependency_paths(&manifest, &temp_manifest_path);
 
-                    let handle = tokio::spawn(async move {
-                        let (tx, mut rx) = tokio::sync::mpsc::channel(10);
+                    let (tx, rx) = mpsc::channel();
+                    let handle = std::thread::spawn(move || {
                         // Setup debouncer. No specific tickrate, max debounce time 2 seconds
                         let mut debouncer =
-                            new_debouncer(std::time::Duration::from_secs(1), None, move |event| {
+                            new_debouncer(Duration::from_secs(1), None, move |event| {
                                 if let Ok(e) = event {
-                                    let _ = tx.blocking_send(e);
+                                    let _ = tx.send(e);
                                 }
                             })
                             .unwrap();
@@ -191,7 +196,7 @@ impl SyncWorkspace {
                             .watch(manifest_dir.as_ref().path(), RecursiveMode::NonRecursive)
                             .unwrap();
 
-                        while let Some(_events) = rx.recv().await {
+                        while let Ok(_events) = rx.recv() {
                             // Rescan the Forc.toml and convert
                             // relative paths to absolute. Save into our temp directory.
                             edit_manifest_dependency_paths(&manifest, &temp_manifest_path);

sway-lsp/src/utils/keyword_docs.rs

@@ -837,8 +837,8 @@ fn extract_lit(tokens: TokenStream) -> String {
     res
 }
 
-#[tokio::test]
-async fn keywords_in_sync() {
+#[test]
+fn keywords_in_sync() {
     let keyword_docs = KeywordDocs::new();
     let lsp_keywords: Vec<_> = keyword_docs.keys().collect();
     let compiler_keywords: Vec<_> = sway_parse::RESERVED_KEYWORDS