refactor(fs): reduce overhead of `watch`

.changes/fs-watch-cleanup.md

@@ -0,0 +1,6 @@
+---
+fs: minor
+fs-js: minor
+---
+
+Reduce the overhead of `watch` and `unwatch`

examples/api/src/views/FileSystem.svelte

@@ -2,16 +2,18 @@
   import * as fs from "@tauri-apps/plugin-fs";
   import { convertFileSrc } from "@tauri-apps/api/core";
   import { arrayBufferToBase64 } from "../lib/utils";
+  import { onDestroy } from "svelte";
 
   export let onMessage;
   export let insecureRenderHtml;
 
   let path = "";
   let img;
+  /** @type {fs.FileHandle} */
   let file;
   let renameTo;
   let watchPath = "";
-  let watchDebounceDelay = 0;
+  let watchDebounceDelay = "0";
   let watchRecursive = false;
   let unwatchFn;
   let unwatchPath = "";
@@ -118,7 +120,7 @@
                     .getElementById("file-save")
                     .addEventListener("click", function () {
                       fs.writeTextFile(path, fileInput.value, {
-                        dir: getDir(),
+                        baseDir: getDir(),
                       }).catch(onMessage);
                     });
                 });
@@ -170,6 +172,15 @@
     unwatchFn = undefined;
     unwatchPath = undefined;
   }
+
+  onDestroy(() => {
+    if (file) {
+      file.close();
+    }
+    if (unwatchFn) {
+      unwatchFn();
+    }
+  })
 </script>
 
 <div class="flex flex-col">

plugins/fs/build.rs

@@ -101,6 +101,7 @@ const COMMANDS: &[(&str, &[&str])] = &[
     ("fstat", &[]),
     ("exists", &[]),
     ("watch", &[]),
+    // TODO: Remove this in v3
     ("unwatch", &[]),
     ("size", &[]),
 ];

plugins/fs/guest-js/index.ts

@@ -1245,15 +1245,23 @@ type WatchEventKindRemove =
   | { kind: 'folder' }
   | { kind: 'other' }
 
+// TODO: Remove this in v3, return `Watcher` instead
 /**
  * @since 2.0.0
  */
 type UnwatchFn = () => void
 
-async function unwatch(rid: number): Promise<void> {
-  await invoke('plugin:fs|unwatch', { rid })
+class Watcher extends Resource {
+  constructor(rid: number) {
+    super(rid)
+  }
+
+  unwatch = () => {
+    void this.close()
+  }
 }
 
+// TODO: Return `Watcher` instead in v3
 /**
  * Watch changes (after a delay) on files or directories.
  *
@@ -1287,11 +1295,12 @@ async function watch(
     onEvent
   })
 
-  return () => {
-    void unwatch(rid)
-  }
+  const watcher = new Watcher(rid)
+
+  return watcher.unwatch
 }
 
+// TODO: Return `Watcher` instead in v3
 /**
  * Watch changes on files or directories.
  *
@@ -1325,9 +1334,9 @@ async function watchImmediate(
     onEvent
   })
 
-  return () => {
-    void unwatch(rid)
-  }
+  const watcher = new Watcher(rid)
+
+  return watcher.unwatch
 }
 
 /**

plugins/fs/src/lib.rs

@@ -420,8 +420,6 @@ pub fn init<R: Runtime>() -> TauriPlugin<R, Option<config::Config>> {
             commands::size,
             #[cfg(feature = "watch")]
             watcher::watch,
-            #[cfg(feature = "watch")]
-            watcher::unwatch
         ])
         .setup(|app, api| {
             let scope = Scope {

plugins/fs/src/watcher.rs

@@ -2,8 +2,8 @@
 // SPDX-License-Identifier: Apache-2.0
 // SPDX-License-Identifier: MIT
 
-use notify::{Config, Event, RecommendedWatcher, RecursiveMode, Watcher};
-use notify_debouncer_full::{new_debouncer, DebounceEventResult, Debouncer, RecommendedCache};
+use notify::{Config, RecommendedWatcher, RecursiveMode, Watcher};
+use notify_debouncer_full::{new_debouncer, DebouncedEvent, Debouncer, RecommendedCache};
 use serde::Deserialize;
 use tauri::{
     ipc::{Channel, CommandScope, GlobalScope},
@@ -11,15 +11,7 @@ use tauri::{
     Manager, Resource, ResourceId, Runtime, Webview,
 };
 
-use std::{
-    path::PathBuf,
-    sync::{
-        mpsc::{channel, Receiver},
-        Mutex,
-    },
-    thread::spawn,
-    time::Duration,
-};
+use std::time::Duration;
 
 use crate::{
     commands::{resolve_path, CommandResult},
@@ -27,51 +19,13 @@ use crate::{
     SafeFilePath,
 };
 
-struct InnerWatcher {
-    pub kind: WatcherKind,
-    paths: Vec<PathBuf>,
-}
-
-pub struct WatcherResource(Mutex<InnerWatcher>);
-impl WatcherResource {
-    fn new(kind: WatcherKind, paths: Vec<PathBuf>) -> Self {
-        Self(Mutex::new(InnerWatcher { kind, paths }))
-    }
-
-    fn with_lock<R, F: FnMut(&mut InnerWatcher) -> R>(&self, mut f: F) -> R {
-        let mut watcher = self.0.lock().unwrap();
-        f(&mut watcher)
-    }
-}
-
-impl Resource for WatcherResource {}
-
+#[allow(unused)]
 enum WatcherKind {
     Debouncer(Debouncer<RecommendedWatcher, RecommendedCache>),
     Watcher(RecommendedWatcher),
 }
 
-fn watch_raw(on_event: Channel<Event>, rx: Receiver<notify::Result<Event>>) {
-    spawn(move || {
-        while let Ok(event) = rx.recv() {
-            if let Ok(event) = event {
-                // TODO: Should errors be emitted too?
-                let _ = on_event.send(event);
-            }
-        }
-    });
-}
-
-fn watch_debounced(on_event: Channel<Event>, rx: Receiver<DebounceEventResult>) {
-    spawn(move || {
-        while let Ok(Ok(events)) = rx.recv() {
-            for event in events {
-                // TODO: Should errors be emitted too?
-                let _ = on_event.send(event.event);
-            }
-        }
-    });
-}
+impl Resource for WatcherKind {}
 
 #[derive(Clone, Deserialize)]
 #[serde(rename_all = "camelCase")]
@@ -86,7 +40,7 @@ pub async fn watch<R: Runtime>(
     webview: Webview<R>,
     paths: Vec<SafeFilePath>,
     options: WatchOptions,
-    on_event: Channel<Event>,
+    on_event: Channel<notify::Event>,
     global_scope: GlobalScope<Entry>,
     command_scope: CommandScope<Entry>,
 ) -> CommandResult<ResourceId> {
@@ -107,52 +61,40 @@ pub async fn watch<R: Runtime>(
         RecursiveMode::NonRecursive
     };
 
-    let kind = if let Some(delay) = options.delay_ms {
-        let (tx, rx) = channel();
-        let mut debouncer = new_debouncer(Duration::from_millis(delay), None, tx)?;
+    let watcher_kind = if let Some(delay) = options.delay_ms {
+        let mut debouncer = new_debouncer(
+            Duration::from_millis(delay),
+            None,
+            move |events: Result<Vec<DebouncedEvent>, Vec<notify::Error>>| {
+                if let Ok(events) = events {
+                    for event in events {
+                        // TODO: Should errors be emitted too?
+                        let _ = on_event.send(event.event);
+                    }
+                }
+            },
+        )?;
         for path in &resolved_paths {
             debouncer.watch(path, recursive_mode)?;
         }
-        watch_debounced(on_event, rx);
         WatcherKind::Debouncer(debouncer)
     } else {
-        let (tx, rx) = channel();
-        let mut watcher = RecommendedWatcher::new(tx, Config::default())?;
+        let mut watcher = RecommendedWatcher::new(
+            move |event| {
+                if let Ok(event) = event {
+                    // TODO: Should errors be emitted too?
+                    let _ = on_event.send(event);
+                }
+            },
+            Config::default(),
+        )?;
         for path in &resolved_paths {
             watcher.watch(path, recursive_mode)?;
         }
-        watch_raw(on_event, rx);
         WatcherKind::Watcher(watcher)
     };
 
-    let rid = webview
-        .resources_table()
-        .add(WatcherResource::new(kind, resolved_paths));
+    let rid = webview.resources_table().add(watcher_kind);
 
     Ok(rid)
 }
-
-#[tauri::command]
-pub async fn unwatch<R: Runtime>(webview: Webview<R>, rid: ResourceId) -> CommandResult<()> {
-    let watcher = webview.resources_table().take::<WatcherResource>(rid)?;
-    WatcherResource::with_lock(&watcher, |watcher| {
-        match &mut watcher.kind {
-            WatcherKind::Debouncer(ref mut debouncer) => {
-                for path in &watcher.paths {
-                    debouncer.unwatch(path).map_err(|e| {
-                        format!("failed to unwatch path: {} with error: {e}", path.display())
-                    })?;
-                }
-            }
-            WatcherKind::Watcher(ref mut w) => {
-                for path in &watcher.paths {
-                    w.unwatch(path).map_err(|e| {
-                        format!("failed to unwatch path: {} with error: {e}", path.display())
-                    })?;
-                }
-            }
-        }
-
-        Ok(())
-    })
-}