Migrate file watchers from fs.watch to VS Code FileSystemWatcher API

Replace Node.js fs.watch with VS Code's FileSystemWatcher to fix Windows
test timeout caused by endless file events bug (nodejs/node#61398).

Changes:
- src/util/watch.ts: New watchFile() function using workspace.createFileSystemWatcher
  with RelativePattern for reliable cross-platform file watching
- src/explorer.ts: Migrate kubeconfig watching to new API with callback pattern
- src/serverlessFunction/functionModel.ts: Replace multiple fs.watch calls with
  single glob pattern watcher for func.yaml files
- src/util/workspace.ts: Enhanced devfile watching to support all valid extensions
  (.yaml, .yml, .json for both devfile and .devfile variants)
- test/unit/util/watch.test.ts: New unit tests with proper VS Code API mocking
  (tests API contract without requiring full extension host)
- test/integration/watch.test.ts: Integration test for real file watching behavior
  (requires full VS Code environment)
- .gitignore: Add .claude/ directory

Benefits:
- Fixes Windows fs.watch endless events bug (VS Code uses parcel-watcher)
- Better performance (runs in VS Code's UtilityProcess)
- Cleaner code (callbacks instead of EventEmitters)
- More complete devfile detection (all valid extensions)

See:
- nodejs/node#61398 (fs.watch endless file events on Windows)
- microsoft/vscode#287800 (100% CPU on Windows with fs.watch)
- https://github.com/microsoft/vscode/wiki/File-Watcher-Internals (VS Code file watcher implementation)

Signed-off-by: Victor Rubezhny <vrubezhny@redhat.com>
Assisted-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: vrubezhny

.gitignore

@@ -11,4 +11,4 @@ dist/
 public/
 test-resources/
 .DS_Store
-
+.claude/

src/explorer.ts

@@ -37,7 +37,7 @@ import { LoginUtil } from './util/loginUtil';
 import { Platform } from './util/platform';
 import { Progress } from './util/progress';
 import { ExecutionContext, imagePath } from './util/utils';
-import { FileContentChangeNotifier, WatchUtil } from './util/watch';
+import { watchFile } from './util/watch';
 import { vsCommand } from './vscommand';
 import { CustomResourceDefinitionStub, K8sResourceKind } from './webview/common/createServiceTypes';
 import { OpenShiftTerminalManager } from './webview/openshift-terminal/openShiftTerminal';
@@ -105,7 +105,7 @@ export class OpenShiftExplorer implements TreeDataProvider<ExplorerItem>, Dispos
 
     private treeView: TreeView<ExplorerItem>;
 
-    private kubeConfigWatchers: FileContentChangeNotifier[];
+    private kubeConfigWatchers: Disposable[];
     private kubeContext: Context;
     private kubeConfigInfo: KubeConfigInfo;
 
@@ -129,29 +129,28 @@ export class OpenShiftExplorer implements TreeDataProvider<ExplorerItem>, Dispos
         try {
             const kubeconfigFiles = getKubeConfigFiles();
             this.kubeConfigWatchers = (!kubeconfigFiles || kubeconfigFiles.length === 0) ? [] :
-                kubeconfigFiles.map(kubeconfigFile => WatchUtil.watchFileForContextChange(path.dirname(kubeconfigFile), path.basename(kubeconfigFile)));
+                kubeconfigFiles.map(kubeconfigFile =>
+                    watchFile(kubeconfigFile, () => {
+                        const kci2 = new KubeConfigInfo();
+                        const kc2 = kci2.getEffectiveKubeConfig();
+                        const newCtx = kc2.getContextObject(kc2.currentContext);
+                        if (Boolean(this.kubeContext) !== Boolean(newCtx)
+                            || (this.kubeContext?.cluster !== newCtx?.cluster
+                                || this.kubeContext?.user !== newCtx?.user
+                                || this.kubeContext?.namespace !== newCtx?.namespace)) {
+                            this.refresh();
+                            this.onDidChangeContextEmitter.fire(newCtx?.name); // newCtx can be 'null'
+                        }
+                        this.kubeContext = newCtx;
+                        this.kubeConfigInfo = kci2;
+                    })
+                );
             if (this.kubeConfigWatchers.length === 0) {
                 void window.showWarningMessage('Kubernetes configuration file(s) not found. Make sure that "${HOME}/.kube/config" file exists or "KUBECONFIG" environment variable is properly configured');
             }
         } catch {
             void window.showWarningMessage('Couldn\'t install watcher for Kubernetes configuration file. OpenShift Application Explorer view won\'t be updated automatically.');
         }
-        for (const fsw of this.kubeConfigWatchers) {
-            fsw.emitter?.on('file-changed', () => {
-                const kci2 = new KubeConfigInfo();
-                const kc2 = kci2.getEffectiveKubeConfig();
-                const newCtx = kc2.getContextObject(kc2.currentContext);
-                if (Boolean(this.kubeContext) !== Boolean(newCtx)
-                    || (this.kubeContext?.cluster !== newCtx?.cluster
-                        || this.kubeContext?.user !== newCtx?.user
-                        || this.kubeContext?.namespace !== newCtx?.namespace)) {
-                    this.refresh();
-                    this.onDidChangeContextEmitter.fire(newCtx?.name); // newCtx can be 'null'
-                }
-                this.kubeContext = newCtx;
-                this.kubeConfigInfo = kci2;
-            });
-        }
         this.treeView = window.createTreeView<ExplorerItem>('openshiftProjectExplorer', {
             treeDataProvider: this,
         });
@@ -804,8 +803,8 @@ export class OpenShiftExplorer implements TreeDataProvider<ExplorerItem>, Dispos
     }
 
     dispose(): void {
-        for (const fsw of this.kubeConfigWatchers) {
-            fsw?.watcher?.close();
+        for (const watcher of this.kubeConfigWatchers) {
+            watcher?.dispose();
         }
         this.treeView.dispose();
     }

src/serverlessFunction/functionModel.ts

@@ -5,7 +5,7 @@
 
 import * as fs from 'fs-extra';
 import * as path from 'path';
-import { Disposable, Uri, window, workspace } from 'vscode';
+import { Disposable, FileSystemWatcher, Uri, workspace } from 'vscode';
 import { CommandText } from '../base/command';
 import { CliChannel } from '../cli';
 import { DeploymentConfig } from '../k8s/deploymentConfig';
@@ -15,19 +15,17 @@ import { DeployedFunction, FunctionContent, FunctionObject, FunctionStatus, Func
 
 export class ServerlessFunctionModel implements Disposable {
 
-    private watchers: fs.FSWatcher[] = [];
+    private funcYamlWatcher: FileSystemWatcher;
     private workspaceWatcher: Disposable;
     private view: FunctionView;
 
     public constructor(view: FunctionView) {
         this.view = view;
-        this.addWatchers();
+        this.setupWatchers();
         this.workspaceWatcher = workspace.onDidChangeWorkspaceFolders((_e) => {
-            for (const watcher of this.watchers) {
-                watcher.close();
-            }
+            this.funcYamlWatcher?.dispose();
             this.view.refresh();
-            this.addWatchers();
+            this.setupWatchers();
         });
     }
 
@@ -101,10 +99,8 @@ export class ServerlessFunctionModel implements Disposable {
     }
 
     public dispose() {
-        for (const watcher of this.watchers) {
-            watcher.close();
-        }
-        this.workspaceWatcher.dispose();
+        this.funcYamlWatcher?.dispose();
+        this.workspaceWatcher?.dispose();
     }
 
     private getDeployFunction(
@@ -132,28 +128,13 @@ export class ServerlessFunctionModel implements Disposable {
         return Functions.imageRegex.test(yamlContent?.image);
     }
 
-    private addWatchers() {
-        if (workspace.workspaceFolders) {
-            for (const workspaceFolder of workspace.workspaceFolders) {
-                let folderExists = false;
-                try {
-                    fs.accessSync(workspaceFolder.uri.fsPath);
-                    folderExists = true;
-                } catch {
-                    // folder doesn't exist
-                    void window.showErrorMessage(`Can't keep track of if '${path.basename(workspaceFolder.uri.fsPath)}' contains a serverless function, since it's been deleted.`);
-                }
-                if (folderExists) {
-                    this.watchers.push(
-                        fs.watch(workspaceFolder.uri.fsPath, (_event, filename) => {
-                            if (filename === 'func.yaml') {
-                                this.view.refresh();
-                            }
-                        }),
-                    );
-                }
-            }
-        }
+    private setupWatchers() {
+        // Watch for func.yaml files across all workspace folders using VS Code's FileSystemWatcher
+        // This is more reliable than fs.watch, especially on Windows
+        this.funcYamlWatcher = workspace.createFileSystemWatcher('**/func.yaml');
+        this.funcYamlWatcher.onDidChange(() => this.view.refresh());
+        this.funcYamlWatcher.onDidCreate(() => this.view.refresh());
+        this.funcYamlWatcher.onDidDelete(() => this.view.refresh());
     }
 
     private async getListItems(command: CommandText, fail = false) {

src/util/watch.ts

@@ -3,36 +3,30 @@
  *  Licensed under the MIT License. See LICENSE file in the project root for license information.
  *-----------------------------------------------------------------------------------------------*/
 
-import { EventEmitter } from 'events';
-import * as fs from 'fs';
-import { FSWatcher } from 'fs-extra';
-import { Util as fsxt } from '../util/utils';
+import * as path from 'path';
+import { Disposable, FileSystemWatcher, RelativePattern, workspace } from 'vscode';
 
-export class WatchUtil {
-    static watchFileForContextChange(
-        location: string,
-        filename: string,
-    ): FileContentChangeNotifier {
-        const emitter: EventEmitter = new EventEmitter();
-        let timer: ReturnType<typeof setInterval> | undefined;
-        fsxt.ensureDirSync(location);
-        const watcher: FSWatcher = fsxt.watch(location, (eventType, changedFile) => {
-            if (filename === changedFile) {
-                if (timer) {
-                    clearTimeout(timer);
-                }
-                timer = setTimeout(() => {
-                    timer = undefined;
-                    emitter.emit('file-changed');
-                }, 500);
-            }
-        });
-        return { watcher, emitter };
-    }
+/**
+ * Watch a specific file for changes using VS Code's FileSystemWatcher API.
+ * This uses VS Code's parcel-watcher implementation which is more reliable than fs.watch,
+ * especially on Windows where fs.watch has known issues with endless events.
+ *
+ * @param filePath Absolute path to the file to watch
+ * @param onChange Callback invoked when the file changes
+ * @returns Disposable to stop watching
+ */
+export function watchFile(filePath: string, onChange: () => void): Disposable {
+    const dir = path.dirname(filePath);
+    const filename = path.basename(filePath);
 
-}
+    const watcher: FileSystemWatcher = workspace.createFileSystemWatcher(
+        new RelativePattern(dir, filename),
+        true,  // ignoreCreateEvents
+        false, // ignoreChangeEvents (we want these!)
+        true   // ignoreDeleteEvents
+    );
+
+    watcher.onDidChange(onChange);
 
-export interface FileContentChangeNotifier {
-    readonly watcher: fs.FSWatcher;
-    readonly emitter: EventEmitter;
+    return watcher;
 }

src/util/workspace.ts

@@ -17,6 +17,16 @@ export const AddWorkspaceFolder: QuickPickItem = {
     description: 'Folder which does not have an OpenShift context',
 };
 
+// Extract devfile patterns as constants
+const DEVFILE_NAMES = ['devfile', '.devfile'] as const;
+const DEVFILE_EXTENSIONS = ['yaml', 'yml', 'json'] as const;
+const DEVFILE_GLOB_PATTERN = `**/{${DEVFILE_NAMES.join(',')}}.{${DEVFILE_EXTENSIONS.join(',')}}`;
+
+// Pre-calculate devfile candidates once at module load
+const DEVFILE_CANDIDATES = DEVFILE_NAMES.flatMap(name =>
+    DEVFILE_EXTENSIONS.map(ext => `${name}.${ext}`)
+);
+
 function isFile(path: string) {
     try {
         return fs.statSync(path).isFile()
@@ -26,9 +36,9 @@ function isFile(path: string) {
 }
 
 function isComponentorFunction(folder: WorkspaceFolder) {
-    return !isFile(path.join(folder.uri.fsPath, 'devfile.yaml'))
-        && !isFile(path.join(folder.uri.fsPath, '.devfile.yaml'))
-        && !isFile(path.join(folder.uri.fsPath, 'func.yaml'));
+    return !DEVFILE_CANDIDATES.some(candidate =>
+        isFile(path.join(folder.uri.fsPath, candidate))
+    ) && !isFile(path.join(folder.uri.fsPath, 'func.yaml'));
 }
 
 function componentAndFuctionFilter(wsFolder: WorkspaceFolder) {
@@ -158,7 +168,7 @@ async function updateDevfileContext(_: unknown) {
  */
 export function setupWorkspaceDevfileContext(): Disposable {
     void updateDevfileContext(undefined);
-    const devfileWatcher = workspace.createFileSystemWatcher('**/{devfile,.devfile}.yaml');
+    const devfileWatcher = workspace.createFileSystemWatcher(DEVFILE_GLOB_PATTERN);
     devfileWatcher.onDidCreate(updateDevfileContext);
     devfileWatcher.onDidDelete(updateDevfileContext);
     workspace.onDidChangeWorkspaceFolders(updateDevfileContext);

test/integration/watch.test.ts

@@ -0,0 +1,72 @@
+/*-----------------------------------------------------------------------------------------------
+ *  Copyright (c) Red Hat, Inc. All rights reserved.
+ *  Licensed under the MIT License. See LICENSE file in the project root for license information.
+ *-----------------------------------------------------------------------------------------------*/
+
+import * as chai from 'chai';
+import * as path from 'path';
+import * as tmp from 'tmp';
+import { Util as fs } from '../../src/util/utils';
+import { watchFile } from '../../src/util/watch';
+
+const {expect} = chai;
+
+suite('File Watch Utility', () => {
+
+    test('watchFile calls the callback when file changes', async () => {
+        // Create a temp file
+        const tmpFile = tmp.fileSync({dir:`${path.basename(tmp.dirSync().name)}`});
+        const fileToWatch = fs.realpathSync(tmpFile.name);
+        fs.ensureFileSync(fileToWatch);
+
+        // Set up the file watcher
+        let changeDetected = false;
+        const watcher = watchFile(fileToWatch, () => {
+            changeDetected = true;
+        });
+
+        // Write to the file after a delay
+        setTimeout(() => {
+            fs.writeFileSync(fileToWatch, 'current-context:test2');
+        }, 500);
+
+        // Wait for the change to be detected
+        return new Promise<void>((resolve) => {
+            const checkInterval = setInterval(() => {
+                if (changeDetected) {
+                    clearInterval(checkInterval);
+                    expect(changeDetected).to.be.true;
+                    resolve();
+                }
+            }, 100);
+
+            // Timeout after 5 seconds
+            setTimeout(() => {
+                clearInterval(checkInterval);
+                if (!changeDetected) {
+                    throw new Error('File change was not detected within timeout');
+                }
+            }, 5000);
+        }).finally(() => {
+            watcher?.dispose();
+            tmpFile.removeCallback();
+        });
+    });
+
+    test('watchFile returns a Disposable', () => {
+        const tmpFile = tmp.fileSync();
+        const fileToWatch = tmpFile.name;
+
+        const watcher = watchFile(fileToWatch, () => {
+            // callback
+        });
+
+        try {
+            expect(watcher).to.have.property('dispose');
+            expect(watcher.dispose).to.be.a('function');
+        } finally {
+            watcher?.dispose();
+            tmpFile.removeCallback();
+        }
+    });
+});