moduleNameMapper override for tslib is causing error when using esm

[viceice]

🐛 Bug Report

I'm using an angular nx workspace with jest projects. I need to use esm because i've some web worker usages.

See error below. My workaround is to set allowJs=true to my tsconfig.spec.json so tslib will be compiled by this project.

To Reproduce

Steps to reproduce the behavior:

Create a nx workspoace with angular preset and some dummy libs.
Configure for esm and run tests.

Expected behavior

Simply run tests without explicit workaround.

Link to repo (highly encouraged)

I can provide a sample maybe later.

Error log:

# content of error stacktrace :
C:\Users\kriese\projects\visualon\xfab\sx\node_modules\tslib\tslib.es6.js:24
    export function __extends(d, b) {
    ^^^^^^

    SyntaxError: Unexpected token 'export'

      at Runtime.createScriptFromCode (../../node_modules/jest-runtime/build/index.js:1479:14)

envinfo

System: 
    OS: Windows 10 21H1

Npm packages:
    jest: 27.0.6
    jest-preset-angular: 9.0.5
    typescript: 4.3.5
    tslib: 2.3.0

[viceice]

I think it's because of this line

jest-preset-angular/presets/index.js

Line 30 in cf3874b

tslib: 'tslib/tslib.es6.js',

[ahnpnl]

We have 2 choices here: either always set allowJs: true internally or remove the mapping of tslib. I prefer the 1st choice as mapping tslib is required if running Jest in ESM mode.