Support string types in dynamic import types.

Search Terms

dynamic import type

Suggestion

I'd like to define a function that wraps a dynamic require or import. Specifically, I'm writing a library that uses node's worker_thread and I want to support 'dependency injection' via dynamic import. You can't pass class instances or functions across execution contexts.

import { isMainThread, Worker, workerData } from 'worker_threads';

export type LoggerImportPath = ???;

export default function lib(logger: LoggerImportPath): Worker {
  return new Worker(__filename, { workerData: { logger });
}

if (!isMainThread) {
  const module: { default: Logger } = await import(workerData.logger);
}

// no type error, ./path/to/logger exports a Logger.
lib(`${__filename}/path/to/logger');

// this should be a type error: import('not-a-module') is not assignable to { default: Logger };
lib('not-a-module');

I don't think you can currently define LoggerImportPath any more precisely than string and import(path: string) returns Promise<any>.

// this returns `{ default: Logger}`
await import('path');

// this returns `any`
const wrapper = path => import(path);
const module: any = await wrapper('path')

Use Cases

I haven't seen this pattern in any other libraries, but I think it's a good way to pass classes or functions across threads or execution contexts. You can't currently limit the kinds of strings that library uses can pass when a module path is expected.

Examples

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

Es sind keine Repository-Dateien, Tests oder Einstiegspunkte genannt. Beginne damit, die Beispiele für den literalen dynamischen Import und den Wrapper mit String-Parameter in einem TypeScript-Projekt zu reproduzieren, und verfolge anschließend für jedes Beispiel das bestehende Verhalten der Typprüfung. Als abgeschlossen gilt die Aufgabe, wenn der angeforderte stringbasierte Importtyp spezifiziert und durch Tests abgedeckt ist, einschließlich sowohl des gültigen logger-Pfads als auch der Fälle mit ungültigem Modulpfad.