kqueue: Only make a single syscall to add all the watches

notify/src/fsevent.rs

@@ -585,7 +585,7 @@ fn test_fsevent_watcher_drop() {
     let (tx, rx) = std::sync::mpsc::channel();
 
     {
-        let mut watcher = FsEventWatcher::new(tx).unwrap();
+        let mut watcher = FsEventWatcher::new(tx, Default::default()).unwrap();
         watcher.watch(dir.path(), RecursiveMode::Recursive).unwrap();
         thread::sleep(Duration::from_millis(2000));
         println!("is running -> {}", watcher.is_running());

notify/src/kqueue.rs

@@ -5,7 +5,7 @@
 //! pieces of kernel code termed filters.
 
 use super::event::*;
-use super::{Error, EventHandler, RecursiveMode, Result, Watcher, Config};
+use super::{Config, Error, EventHandler, RecursiveMode, Result, Watcher};
 use crate::{unbounded, Receiver, Sender};
 use kqueue::{EventData, EventFilter, FilterFlag, Ident};
 use std::collections::HashMap;
@@ -288,18 +288,23 @@ impl EventLoop {
         // If the watch is not recursive, or if we determine (by stat'ing the path to get its
         // metadata) that the watched path is not a directory, add a single path watch.
         if !is_recursive || !metadata(&path).map_err(Error::io)?.is_dir() {
-            return self.add_single_watch(path, false);
+            self.add_single_watch(path, false)?;
+        } else {
+            for entry in WalkDir::new(path).follow_links(true).into_iter() {
+                let entry = entry.map_err(map_walkdir_error)?;
+                self.add_single_watch(entry.path().to_path_buf(), is_recursive)?;
+            }
         }
 
-        for entry in WalkDir::new(path).follow_links(true).into_iter() {
-            let entry = entry.map_err(map_walkdir_error)?;
-            self.add_single_watch(entry.path().to_path_buf(), is_recursive)?;
-        }
+        // Only make a single `kevent` syscall to add all the watches.
         self.kqueue.watch()?;
 
         Ok(())
     }
 
+    /// Adds a single watch to the kqueue.
+    ///
+    /// The caller of this function must call `self.kqueue.watch()` afterwards to register the new watch.
     fn add_single_watch(&mut self, path: PathBuf, is_recursive: bool) -> Result<()> {
         let event_filter = EventFilter::EVFILT_VNODE;
         let filter_flags = FilterFlag::NOTE_DELETE
@@ -314,7 +319,7 @@ impl EventLoop {
             .add_filename(&path, event_filter, filter_flags)
             .map_err(|e| Error::io(e).add_path(path.clone()))?;
         self.watches.insert(path, is_recursive);
-        self.kqueue.watch()?;
+
         Ok(())
     }