BREAKING CHANGE(watchers): Replace polling-based write stabilization with debounce-based event coalescing and simplify watcher options

ts/watchers/watcher.deno.ts

@@ -65,10 +65,9 @@ export class DenoWatcher implements IWatcher {
   private watcher: ReturnType<typeof Deno.watchFs> | null = null;
   private watchedFiles: Set<string> = new Set();
   private _isWatching = false;
-  private abortController: AbortController | null = null;
-  private recentEvents: Map<string, number> = new Map();
-  private throttleMs = 50;
-  private pendingWrites: Map<string, ReturnType<typeof setTimeout>> = new Map();
+
+  // Debounce: pending emits per file path
+  private pendingEmits: Map<string, ReturnType<typeof setTimeout>> = new Map();
 
   public readonly events$ = new smartrx.rxjs.Subject<IWatchEvent>();
 
@@ -97,8 +96,6 @@ export class DenoWatcher implements IWatcher {
     }
 
     try {
-      this.abortController = new AbortController();
-
       // Start watching all base paths
       this.watcher = Deno.watchFs(this.options.basePaths, { recursive: true });
       this._isWatching = true;
@@ -122,11 +119,11 @@ export class DenoWatcher implements IWatcher {
   async stop(): Promise<void> {
     this._isWatching = false;
 
-    // Cancel all pending write stabilizations
-    for (const timeout of this.pendingWrites.values()) {
+    // Cancel all pending debounced emits
+    for (const timeout of this.pendingEmits.values()) {
       clearTimeout(timeout);
     }
-    this.pendingWrites.clear();
+    this.pendingEmits.clear();
 
     // Close the watcher
     if (this.watcher) {
@@ -135,7 +132,6 @@ export class DenoWatcher implements IWatcher {
     }
 
     this.watchedFiles.clear();
-    this.recentEvents.clear();
   }
 
   /**
@@ -153,7 +149,7 @@ export class DenoWatcher implements IWatcher {
         }
 
         for (const filePath of event.paths) {
-          await this.handleDenoEvent(event.kind, filePath);
+          this.handleDenoEvent(event.kind, filePath);
         }
       }
     } catch (error: any) {
@@ -164,12 +160,12 @@ export class DenoWatcher implements IWatcher {
   }
 
   /**
-   * Handle a Deno file system event
+   * Handle a Deno file system event - debounce and normalize
    */
-  private async handleDenoEvent(
+  private handleDenoEvent(
     kind: 'create' | 'modify' | 'remove' | 'access' | 'any' | 'other',
     filePath: string
-  ): Promise<void> {
+  ): void {
     // Ignore 'access' events (just reading the file)
     if (kind === 'access') {
       return;
@@ -180,14 +176,30 @@ export class DenoWatcher implements IWatcher {
       return;
     }
 
-    // Throttle duplicate events
-    if (!this.shouldEmit(filePath, kind)) {
-      return;
+    // Debounce: cancel any pending emit for this file
+    const existing = this.pendingEmits.get(filePath);
+    if (existing) {
+      clearTimeout(existing);
     }
 
+    // Schedule debounced emit
+    const timeout = setTimeout(() => {
+      this.pendingEmits.delete(filePath);
+      this.emitFileEvent(filePath, kind);
+    }, this.options.debounceMs);
+
+    this.pendingEmits.set(filePath, timeout);
+  }
+
+  /**
+   * Emit the actual file event after debounce
+   */
+  private async emitFileEvent(
+    filePath: string,
+    kind: 'create' | 'modify' | 'remove' | 'access' | 'any' | 'other'
+  ): Promise<void> {
     try {
       if (kind === 'create') {
-        // Create events (atomic saves) don't need stabilization - file is already complete
         const stats = await this.statSafe(filePath);
         if (stats) {
           this.watchedFiles.add(filePath);
@@ -195,16 +207,9 @@ export class DenoWatcher implements IWatcher {
           this.events$.next({ type: eventType, path: filePath, stats });
         }
       } else if (kind === 'modify') {
-        // Modify events are in-place writes - use stabilization
         const stats = await this.statSafe(filePath);
         if (stats && !stats.isDirectory()) {
-          // Wait for write to stabilize
-          await this.waitForWriteFinish(filePath);
-          const finalStats = await this.statSafe(filePath);
-
-          if (finalStats) {
-            this.events$.next({ type: 'change', path: filePath, stats: finalStats });
-          }
+          this.events$.next({ type: 'change', path: filePath, stats });
         }
       } else if (kind === 'remove') {
         const wasDirectory = this.isKnownDirectory(filePath);
@@ -219,52 +224,6 @@ export class DenoWatcher implements IWatcher {
     }
   }
 
-  /**
-   * Wait for file write to complete (polling-based)
-   */
-  private async waitForWriteFinish(filePath: string): Promise<void> {
-    return new Promise((resolve) => {
-      let lastSize = -1;
-      let lastChange = Date.now();
-      const startTime = Date.now();
-
-      const poll = async () => {
-        try {
-          const stats = await this.statSafe(filePath);
-          if (!stats) {
-            resolve();
-            return;
-          }
-
-          const now = Date.now();
-
-          // Check if we've exceeded max wait time - resolve immediately
-          if (now - startTime >= this.options.maxWaitTime) {
-            this.pendingWrites.delete(filePath);
-            resolve();
-            return;
-          }
-
-          if (stats.size !== lastSize) {
-            lastSize = stats.size;
-            lastChange = now;
-            this.pendingWrites.set(filePath, setTimeout(poll, this.options.pollInterval));
-          } else if (now - lastChange >= this.options.stabilityThreshold) {
-            this.pendingWrites.delete(filePath);
-            resolve();
-          } else {
-            this.pendingWrites.set(filePath, setTimeout(poll, this.options.pollInterval));
-          }
-        } catch {
-          this.pendingWrites.delete(filePath);
-          resolve();
-        }
-      };
-
-      this.pendingWrites.set(filePath, setTimeout(poll, this.options.pollInterval));
-    });
-  }
-
   /**
    * Scan directory and emit 'add' events for existing files
    */
@@ -276,6 +235,12 @@ export class DenoWatcher implements IWatcher {
     try {
       for await (const entry of Deno.readDir(dirPath)) {
         const fullPath = `${dirPath}/${entry.name}`;
+
+        // Skip temp files during initial scan too
+        if (this.isTemporaryFile(fullPath)) {
+          continue;
+        }
+
         const stats = await this.statSafe(fullPath);
 
         if (!stats) {
@@ -322,31 +287,4 @@ export class DenoWatcher implements IWatcher {
     }
     return false;
   }
-
-  /**
-   * Throttle duplicate events
-   */
-  private shouldEmit(filePath: string, eventType: string): boolean {
-    const key = `${filePath}:${eventType}`;
-    const now = Date.now();
-    const lastEmit = this.recentEvents.get(key);
-
-    if (lastEmit && now - lastEmit < this.throttleMs) {
-      return false;
-    }
-
-    this.recentEvents.set(key, now);
-
-    // Clean up old entries periodically
-    if (this.recentEvents.size > 1000) {
-      const cutoff = now - this.throttleMs * 2;
-      for (const [k, time] of this.recentEvents) {
-        if (time < cutoff) {
-          this.recentEvents.delete(k);
-        }
-      }
-    }
-
-    return true;
-  }
 }