Implement async parsers (#1352)

packages/langium/src/default-module.ts

@@ -34,6 +34,7 @@ import { DefaultCommentProvider } from './documentation/comment-provider.js';
 import { LangiumParserErrorMessageProvider } from './parser/langium-parser.js';
 import { DefaultAsyncParser } from './parser/async-parser.js';
 import { DefaultWorkspaceLock } from './workspace/workspace-lock.js';
+import { DefaultHydrator } from './serializer/hydrator.js';
 
 /**
  * Context required for creating the default language-specific dependency injection module.
@@ -75,6 +76,7 @@ export function createDefaultCoreModule(context: DefaultCoreModuleContext): Modu
             References: (services) => new DefaultReferences(services)
         },
         serializer: {
+            Hydrator: (services) => new DefaultHydrator(services),
             JsonSerializer: (services) => new DefaultJsonSerializer(services)
         },
         validation: {

packages/langium/src/grammar/langium-grammar-module.ts

@@ -67,10 +67,12 @@ export const LangiumGrammarModule: Module<LangiumGrammarServices, PartialLangium
  *
  * @param context Shared module context, used to create additional shared modules
  * @param sharedModule Existing shared module to inject together with new shared services
+ * @param module Additional/modified service implementations for the language services
  * @returns Shared services enriched with LSP services + Grammar services, per usual
  */
 export function createLangiumGrammarServices(context: DefaultSharedModuleContext,
-    sharedModule?: Module<LangiumSharedServices, PartialLangiumSharedServices>): {
+    sharedModule?: Module<LangiumSharedServices, PartialLangiumSharedServices>,
+    module?: Module<LangiumServices, PartialLangiumServices>): {
         shared: LangiumSharedServices,
         grammar: LangiumGrammarServices
     } {
@@ -82,7 +84,8 @@ export function createLangiumGrammarServices(context: DefaultSharedModuleContext
     const grammar = inject(
         createDefaultModule({ shared }),
         LangiumGrammarGeneratedModule,
-        LangiumGrammarModule
+        LangiumGrammarModule,
+        module
     );
     addTypeCollectionPhase(shared, grammar);
     shared.ServiceRegistry.register(grammar);

packages/langium/src/node/index.ts

@@ -5,3 +5,4 @@
  ******************************************************************************/
 
 export * from './node-file-system-provider.js';
+export * from './worker-thread-async-parser.js';

packages/langium/src/node/worker-thread-async-parser.ts

@@ -0,0 +1,41 @@
+/******************************************************************************
+ * Copyright 2023 TypeFox GmbH
+ * This program and the accompanying materials are made available under the
+ * terms of the MIT License, which is available in the project root.
+ ******************************************************************************/
+
+import type { LangiumCoreServices } from '../services.js';
+import { ParserWorker } from '../parser/async-parser.js';
+import { AbstractThreadedAsyncParser } from '../parser/async-parser.js';
+import { Worker } from 'node:worker_threads';
+
+export class WorkerThreadAsyncParser extends AbstractThreadedAsyncParser {
+
+    protected workerPath: string | (() => string);
+
+    constructor(services: LangiumCoreServices, workerPath: string | (() => string)) {
+        super(services);
+        this.workerPath = workerPath;
+    }
+
+    protected override createWorker(): ParserWorker {
+        const path = typeof this.workerPath === 'function' ? this.workerPath() : this.workerPath;
+        const worker = new Worker(path);
+        const parserWorker = new WorkerThreadParserWorker(worker);
+        return parserWorker;
+    }
+
+}
+
+export class WorkerThreadParserWorker extends ParserWorker {
+
+    constructor(worker: Worker) {
+        super(
+            (message) => worker.postMessage(message),
+            cb => worker.on('message', cb),
+            cb => worker.on('error', cb),
+            () => worker.terminate()
+        );
+    }
+
+}

packages/langium/src/parser/async-parser.ts

@@ -8,6 +8,10 @@ import type { CancellationToken } from '../utils/cancellation.js';
 import type { LangiumCoreServices } from '../services.js';
 import type { AstNode } from '../syntax-tree.js';
 import type { LangiumParser, ParseResult } from './langium-parser.js';
+import type { Hydrator } from '../serializer/hydrator.js';
+import type { Event } from '../utils/event.js';
+import { Deferred, OperationCancelled } from '../utils/promise-utils.js';
+import { Emitter } from '../utils/event.js';
 
 /**
  * Async parser that allows to cancel the current parsing process.
@@ -37,3 +41,156 @@ export class DefaultAsyncParser implements AsyncParser {
         return Promise.resolve(this.syncParser.parse<T>(text));
     }
 }
+
+export abstract class AbstractThreadedAsyncParser implements AsyncParser {
+
+    /**
+     * The thread count determines how many threads are used to parse files in parallel.
+     * The default value is 8. Decreasing this value increases startup performance, but decreases parallel parsing performance.
+     */
+    protected threadCount = 8;
+    /**
+     * The termination delay determines how long the parser waits for a thread to finish after a cancellation request.
+     * The default value is 200(ms).
+     */
+    protected terminationDelay = 200;
+    protected workerPool: ParserWorker[] = [];
+    protected queue: Array<Deferred<ParserWorker>> = [];
+
+    protected readonly hydrator: Hydrator;
+
+    constructor(services: LangiumCoreServices) {
+        this.hydrator = services.serializer.Hydrator;
+    }
+
+    protected initializeWorkers(): void {
+        while (this.workerPool.length < this.threadCount) {
+            const worker = this.createWorker();
+            worker.onReady(() => {
+                if (this.queue.length > 0) {
+                    const deferred = this.queue.shift();
+                    if (deferred) {
+                        worker.lock();
+                        deferred.resolve(worker);
+                    }
+                }
+            });
+            this.workerPool.push(worker);
+        }
+    }
+
+    async parse<T extends AstNode>(text: string, cancelToken: CancellationToken): Promise<ParseResult<T>> {
+        const worker = await this.acquireParserWorker(cancelToken);
+        const deferred = new Deferred<ParseResult<T>>();
+        let timeout: NodeJS.Timeout | undefined;
+        // If the cancellation token is requested, we wait for a certain time before terminating the worker.
+        // Since the cancellation token lives longer than the parsing process, we need to dispose the event listener.
+        // Otherwise, we might accidentally terminate the worker after the parsing process has finished.
+        const cancellation = cancelToken.onCancellationRequested(() => {
+            timeout = setTimeout(() => {
+                this.terminateWorker(worker);
+            }, this.terminationDelay);
+        });
+        worker.parse(text).then(result => {
+            result.value = this.hydrator.hydrate(result.value);
+            deferred.resolve(result as ParseResult<T>);
+        }).catch(err => {
+            deferred.reject(err);
+        }).finally(() => {
+            cancellation.dispose();
+            clearTimeout(timeout);
+        });
+        return deferred.promise;
+    }
+
+    protected terminateWorker(worker: ParserWorker): void {
+        worker.terminate();
+        const index = this.workerPool.indexOf(worker);
+        if (index >= 0) {
+            this.workerPool.splice(index, 1);
+        }
+    }
+
+    protected async acquireParserWorker(cancelToken: CancellationToken): Promise<ParserWorker> {
+        this.initializeWorkers();
+        for (const worker of this.workerPool) {
+            if (worker.ready) {
+                worker.lock();
+                return worker;
+            }
+        }
+        const deferred = new Deferred<ParserWorker>();
+        cancelToken.onCancellationRequested(() => {
+            const index = this.queue.indexOf(deferred);
+            if (index >= 0) {
+                this.queue.splice(index, 1);
+            }
+            deferred.reject('OperationCancelled');
+        });
+        this.queue.push(deferred);
+        return deferred.promise;
+    }
+
+    protected abstract createWorker(): ParserWorker;
+}
+
+export type WorkerMessagePost = (message: unknown) => void;
+export type WorkerMessageCallback = (cb: (message: unknown) => void) => void;
+
+export class ParserWorker {
+
+    protected readonly sendMessage: WorkerMessagePost;
+    protected readonly _terminate: () => void;
+    protected readonly onReadyEmitter = new Emitter<void>();
+
+    protected deferred = new Deferred<ParseResult>();
+    protected _ready = true;
+    protected _parsing = false;
+
+    get ready(): boolean {
+        return this._ready;
+    }
+
+    get onReady(): Event<void> {
+        return this.onReadyEmitter.event;
+    }
+
+    constructor(sendMessage: WorkerMessagePost, onMessage: WorkerMessageCallback, onError: WorkerMessageCallback, terminate: () => void) {
+        this.sendMessage = sendMessage;
+        this._terminate = terminate;
+        onMessage(result => {
+            const parseResult = result as ParseResult;
+            this.deferred.resolve(parseResult);
+            this.unlock();
+        });
+        onError(error => {
+            this.deferred.reject(error);
+            this.unlock();
+        });
+    }
+
+    terminate(): void {
+        this.deferred.reject(OperationCancelled);
+        this._terminate();
+    }
+
+    lock(): void {
+        this._ready = false;
+    }
+
+    unlock(): void {
+        this._parsing = false;
+        this._ready = true;
+        this.onReadyEmitter.fire();
+    }
+
+    parse(text: string): Promise<ParseResult> {
+        if (this._parsing) {
+            throw new Error('Parser worker is busy');
+        }
+        this._parsing = true;
+        this.deferred = new Deferred();
+        this.sendMessage(text);
+        return this.deferred.promise;
+    }
+}