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watcher - defer realpath to only when needed #237600

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Jan 10, 2025
Merged

watcher - defer realpath to only when needed #237600

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73 changes: 33 additions & 40 deletions src/vs/platform/files/node/watcher/nodejs/nodejsWatcherLib.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ import { realpath } from '../../../../../base/node/extpath.js';
import { Promises } from '../../../../../base/node/pfs.js';
import { FileChangeType, IFileChange } from '../../../common/files.js';
import { ILogMessage, coalesceEvents, INonRecursiveWatchRequest, parseWatcherPatterns, IRecursiveWatcherWithSubscribe, isFiltered, isWatchRequestWithCorrelation } from '../../../common/watcher.js';
import { Lazy } from '../../../../../base/common/lazy.js';

export class NodeJSFileWatcherLibrary extends Disposable {

Expand Down Expand Up @@ -55,6 +56,28 @@ export class NodeJSFileWatcherLibrary extends Disposable {

private readonly cts = new CancellationTokenSource();

private readonly realPath = new Lazy(async () => {

// This property is intentionally `Lazy` and not using `realcase()` as the counterpart
// in the recursive watcher because of the amount of paths this watcher is dealing with.
// We try as much as possible to avoid even needing `realpath()` if we can because even
// that method does an `lstat()` per segment of the path.

let result = this.request.path;

try {
result = await realpath(this.request.path);

if (this.request.path !== result) {
this.trace(`correcting a path to watch that seems to be a symbolic link (original: ${this.request.path}, real: ${result})`);
}
} catch (error) {
// ignore
}

return result;
});

readonly ready = this.watch();

private _isReusingRecursiveWatcher = false;
Expand All @@ -76,19 +99,13 @@ export class NodeJSFileWatcherLibrary extends Disposable {

private async watch(): Promise<void> {
try {
const realPath = await this.normalizePath(this.request);
const stat = await promises.stat(this.request.path);

if (this.cts.token.isCancellationRequested) {
return;
}

const stat = await promises.stat(realPath);

if (this.cts.token.isCancellationRequested) {
return;
}

this._register(await this.doWatch(realPath, stat.isDirectory()));
this._register(await this.doWatch(stat.isDirectory()));
} catch (error) {
if (error.code !== 'ENOENT') {
this.error(error);
Expand All @@ -106,46 +123,21 @@ export class NodeJSFileWatcherLibrary extends Disposable {
this.onDidWatchFail?.();
}

private async normalizePath(request: INonRecursiveWatchRequest): Promise<string> {
let realPath = request.path;

try {

// Check for symbolic link
realPath = await realpath(request.path);

// Note: we used to also call `realcase()` here, but
// that operation is very expensive for large amounts
// of files and is actually not needed for single
// file/folder watching where we report on the original
// path anyway.
// (https://github.com/microsoft/vscode/issues/237351)

if (request.path !== realPath) {
this.trace(`correcting a path to watch that seems to be a symbolic link (original: ${request.path}, real: ${realPath})`);
}
} catch (error) {
// ignore
}

return realPath;
}

private async doWatch(realPath: string, isDirectory: boolean): Promise<IDisposable> {
private async doWatch(isDirectory: boolean): Promise<IDisposable> {
const disposables = new DisposableStore();

if (this.doWatchWithExistingWatcher(realPath, isDirectory, disposables)) {
if (this.doWatchWithExistingWatcher(isDirectory, disposables)) {
this.trace(`reusing an existing recursive watcher for ${this.request.path}`);
this._isReusingRecursiveWatcher = true;
} else {
this._isReusingRecursiveWatcher = false;
await this.doWatchWithNodeJS(realPath, isDirectory, disposables);
await this.doWatchWithNodeJS(isDirectory, disposables);
}

return disposables;
}

private doWatchWithExistingWatcher(realPath: string, isDirectory: boolean, disposables: DisposableStore): boolean {
private doWatchWithExistingWatcher(isDirectory: boolean, disposables: DisposableStore): boolean {
if (isDirectory) {
// Recursive watcher re-use is currently not enabled for when
// folders are watched. this is because the dispatching in the
Expand All @@ -162,7 +154,7 @@ export class NodeJSFileWatcherLibrary extends Disposable {
}

if (error) {
const watchDisposable = await this.doWatch(realPath, isDirectory);
const watchDisposable = await this.doWatch(isDirectory);
if (!disposables.isDisposed) {
disposables.add(watchDisposable);
} else {
Expand All @@ -188,7 +180,8 @@ export class NodeJSFileWatcherLibrary extends Disposable {
return false;
}

private async doWatchWithNodeJS(realPath: string, isDirectory: boolean, disposables: DisposableStore): Promise<void> {
private async doWatchWithNodeJS(isDirectory: boolean, disposables: DisposableStore): Promise<void> {
const realPath = await this.realPath.value;

// macOS: watching samba shares can crash VSCode so we do
// a simple check for the file path pointing to /Volumes
Expand Down Expand Up @@ -407,7 +400,7 @@ export class NodeJSFileWatcherLibrary extends Disposable {
if (fileExists) {
this.onFileChange({ resource: requestResource, type: FileChangeType.UPDATED, cId: this.request.correlationId }, true /* skip excludes/includes (file is explicitly watched) */);

watcherDisposables.add(await this.doWatch(realPath, false));
watcherDisposables.add(await this.doWatch(false));
}

// File seems to be really gone, so emit a deleted and failed event
Expand Down
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