Support ESM

🚀 Feature Proposal

Jest is working on supporting ESM https://github.com/facebook/jest/issues/9430 . We should consider lift up the hardcoded target: commonjs at some points.

Related discussion about detecting whether a file is esm or commonjs can be found here https://github.com/facebook/jest/issues/9860

Related issue: #1174

Motivation

Let ts-jest users as well as jest users take part in the ESM support development and testing.

[marcj]

@gadicc you simply import the TS files as usual, omitting the file extension.

[tstelzer]

you simply import the TS files as usual, omitting the file extension.

This doesn’t make sense to me.

In an ESM project, imports will end with .js. Even when I omit the file extension in my test files, the code under test will import other modules, using .js files extensions. In other words:

// file: a.spec.ts
import * as a from './a'; // works

// file: a.ts
import * as b from './b.js'; // "Cannot find module './b.js' from './a.ts'

For what it’s worth, @gadicc workaround seems to work for me.