TS imports with .js extension break Jest-resolve

Issue :

TypeScript files using web-compatible ES6 imports cause Jest to throw an error about not being able to find the module. This error comes from jest-resolve/build/index.js:229 and happens regardless of the module type specified in ts-jest (commonjs, amd, ES6, etc.)

Expected behavior :

TypeScript supports adding a .js extension to import statements for web-compatibility (since imports require a full path, including the extension).

I would expect ts-jest to allow TypeScript to handle this and convert it to commonjs before it gets passed to jest.

Minimal repo :

/* user.ts */
export class User {
  public name : string;

  constructor(name : string) {
    this.name = name;
  }
}

/* user.spec.ts */
import { User } from './user.js';

describe('User', function() {
});

[dpogue]

I set up a custom resolver and just published it to npm: jest-ts-webcompat-resolver

[joeldenning]

I got things working with .js extensions in typescript imports with the following jest.config.js:

/**  @type {import('@jest/types').Config.ProjectConfig} */
const config = {
  transform: {
    "\\.[jt]sx?$": "ts-jest",
  },
  "globals": {
    "ts-jest": {
      "useESM": true
    }
  },
  moduleNameMapper: {
    "(.+)\\.js": "$1"
  },
  extensionsToTreatAsEsm: [".ts"],
};

export default config;