Using webpack worker-loader with typescript causes cannot find module error

Question

I've been using the webpack webworker loader for a while now. And we're now migrating to Angular 7 and started using typescript.

After following many guides and tuturials and this amazing issue post: https://github.com/webpack-contrib/worker-loader/issues/94#issuecomment-336596520

I keep getting errors and do not get the worker-loader to work with typescript.

ERROR in [at-loader] ....../import/worker/index.ts:4:58 TS2306: File '....../import/worker/import.worker.ts' is not a module.

ERROR in [at-loader] ......./import/import.component.ts:13:11 TS2304: Cannot find name 'MyWorkerImport'.

My current setup is as follows:

webpack config:

module: {
    rules: [
        {
            test: /\.worker\.ts$/,
            use: [
                {
                    loader: 'worker-loader',
                    options: {
                        name: '[name].[hash].js',
                        publicPath: '/'
                    }
                },
                {
                    loader: 'awesome-typescript-loader',
                    options: {
                        configFileName: rootPath + '/tsconfig.json'
                    }
                }
            ]
        }
    ]
}

tsconfig.json

{
    "compilerOptions": {
        "target": "es5",
        "module": "commonjs",
        "moduleResolution": "node",
        "sourceMap": true,
        "emitDecoratorMetadata": true,
        "experimentalDecorators": true,
        "lib": [ "es6", "dom" ],
        "noImplicitAny": false,
        "suppressImplicitAnyIndexErrors": true,
        "declaration": false,
        "skipLibCheck": true,
        "types": [
            "node"
        ],
        "typeRoots": [
            "node_modules/@types",
            "typings"
        ]
    },
    "files": []
}

typings/custom.d.ts

declare module 'worker-loader!*' {
    class WebpackWorker extends Worker {
        constructor();
    }

    export = WebpackWorker;
}

worker/import.worker.ts

import { MyWorker, MESSAGE_TYPE } from './types';

const ctx: MyWorker= self as any;

ctx.onmessage = event => {
    const msg = event.data;
    console.log(event);
};

ctx.postMessage({ type: MESSAGE_TYPE.READY });

export default null as any;

worker/index.ts

import { MyWorker} from './types';
import MyWorkerImport = require('./import.worker');

export { MESSAGE_TYPE } from './types';
export default MyWorkerImport as typeof MyWorker;

worker/types.d.ts

// MyWorker/types.d.ts

// Enumerate message types
export const enum MESSAGE_TYPE {
    READY = 'ready',
    REQUEST = 'request',
    RESULT = 'result',
    ERROR = 'error'
}

// Define expected properties for each message type
interface IReadyMessage {
    type: MESSAGE_TYPE.READY;
}

interface IRequestMessage {
    type: MESSAGE_TYPE.REQUEST;
    paramA: string;
    paramB: number;
}

interface IResultMessage {
    type: MESSAGE_TYPE.RESULT;
    data: Float32Array;
}

interface IErrorMessage {
    type: MESSAGE_TYPE.ERROR;
    error: string;
}

// Create a union type of all messages for convenience
type MyWorkerMessage = IReadyMessage | IRequestMessage | IResultMessage | IErrorMessage;

// Extend MessageEvent to use our messages
interface IMyMessageEvent extends MessageEvent {
    data: MyWorkerMessage;
}

// Extend Worker to use our custom MessageEvent
export class MyWorkerWorker extends Worker {
    public onmessage: (this: MyWorker, ev: IMyMessageEvent) => any;

    public postMessage(this:  MyWorker, msg: MyWorkerMessage, transferList?: ArrayBuffer[]): any;
    public addEventListener(type: 'message', listener: (this: MyWorker, ev: IMyMessageEvent) => any, useCapture?: boolean): void;
    public addEventListener(type: 'error', listener: (this: MyWorker, ev: ErrorEvent) => any, useCapture?: boolean): void;
}

import.component.ts

import {Component, OnInit} from '@angular/core';
import MyWorker from "./worker"

@Component({
    templateUrl: './import.a2.html',
    styleUrls: ['./import.a2.scss']
})
export class ImportComponent implements OnInit {

    workers: MyWorker[] = [];

    constructor() {}

    ngOnInit(): void {}

    processFile() {
        const worker = new MyWorker('');
    }

}

And i keep getting the following message:

ERROR in [at-loader] ....../import/worker/index.ts:4:58 TS2306: File '....../import/worker/import.worker.ts' is not a module.

ERROR in [at-loader] ......./import/import.component.ts:13:11 TS2304: Cannot find name 'MyWorkerImport'.

if i change the line to

import MyWorker = require('worker-loader!./import.worker');

The error changes to:

ERROR in [at-loader] ....../import/worker/index.ts:4:58 TS2307: Cannot find module 'worker-loader!./import.worker'.

ERROR in [at-loader] ....../import/import.component.ts:13:11 TS2304: Cannot find name 'MyWorkerImport'.

Answer 1

Ok all an all it's plain and simple. My custom typings file was not included and webpack did not get that.

I changed the custom.d.ts to a folder named custom and a file named index.d.ts resulting in typings/custom/index.d.ts

I changed tsconfig.json to include typings relative and to add custom (since it was fixed at node).

more info on typings here: https://www.typescriptlang.org/docs/handbook/tsconfig-json.html (Search for @typeRoots)

New tsconfig (note the difference in types and typeRoots):

{
    "compilerOptions": {
        "target": "es5",
        "module": "commonjs",
        "moduleResolution": "node",
        "sourceMap": true,
        "emitDecoratorMetadata": true,
        "experimentalDecorators": true,
        "lib": [ "webworker", "es6", "dom" ],
        "noImplicitAny": false,
        "suppressImplicitAnyIndexErrors": true,
        "declaration": false,
        "skipLibCheck": true,
        "types": [
            "node",
            "custom"
        ],
        "typeRoots": [
            "node_modules/@types",
            "./typings"
        ]
    },
    "files": []
}

Next to that you must load the file as

import MyWorker = require('worker-loader!./worker/import.worker');

and you can remove the entire webpack config section