Support Testing with imports of JS files in ESM

Current Behavior

When running test files with that contain ES6 module imports with Jest, I get the following error:

Jest encountered an unexpected token

    This usually means that you are trying to import a file which Jest cannot parse, e.g. it's not plain JavaScript.

    By default, if Jest sees a Babel config, it will use that to transform your files, ignoring "node_modules".

    Here's what you can do:
     • To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
     • If you need a custom transformation specify a "transform" option in your config.
     • If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.

    You'll find more details and examples of these config options in the docs:
    https://jestjs.io/docs/en/configuration.html

Is there an existing recommendation for handling ES6/ESNext module imports, if so, could we add documentation around this? If it doesn’t exist, could we add recommendation on how to handle it? I’m happy to help if I can. Could this be a TSDX feature, to switch on and off?

Desired Behavior

Either handled by default by TSDX, or there is clear recommendations on how best to handle this.

Suggested Solution

Happy to add docs with the recommendation to resolve, although I’m not sure what the recommendations are as yet.

Who does this impact? Who is this for?

Users importing other packages that use ES6.

Describe alternatives you’ve considered

I considered using babel-jest and configuring it myself, but this seems to make TSDX a little redundant.

[karlhorky]

So this was fixed by my #486 very recently

I don’t believe this is fixed yet and this should be reopened.

Using the latest tsdx@0.14.1, Jest tests fail when they import something in ESM (eg. p-map) from node_modules, also when using the NODE_OPTIONS=--experimental-vm-modules option as described in the docs:

Repo: https://github.com/karlhorky/tsdx-test-esm-fail Repl.it (just hit the Run button at the top): https://replit.com/@karlhorky/tsdx-test-esm-fail

$ yarn test     
yarn run v1.22.10
$ tsdx test
 FAIL  test/blah.test.ts
  ● Test suite failed to run

    Jest encountered an unexpected token

    This usually means that you are trying to import a file which Jest cannot parse, e.g. it's not plain JavaScript.

    By default, if Jest sees a Babel config, it will use that to transform your files, ignoring "node_modules".

    Here's what you can do:
     • To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
     • If you need a custom transformation specify a "transform" option in your config.
     • If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.

    You'll find more details and examples of these config options in the docs:
    https://jestjs.io/docs/en/configuration.html

    Details:

    tsdx-test-esm-fail/node_modules/p-map/index.js:1
    ({"Object.<anonymous>":function(module,exports,require,__dirname,__filename,global,jest){import AggregateError from 'aggregate-error';
                                                                                             ^^^^^^

    SyntaxError: Cannot use import statement outside a module

    > 1 | import pMap from 'p-map';
        | ^
      2 |
      3 | console.log('p-map', pMap);
      4 |

      at Runtime.createScriptFromCode (node_modules/jest-runtime/build/index.js:1258:14)
      at Object.<anonymous> (src/index.ts:1:1)

Test Suites: 1 failed, 1 total
Tests:       0 total
Snapshots:   0 total
Time:        1.326s, estimated 2s

[lwazevedo]

Hi,

Any solution to this problem?

I’m going through the same situation.

I have a third-party file in my project that internally imports two libs in js and when I run the test I get this error:

Jest encountered an unexpected token

This usually means that you are trying to import a file which Jest cannot parse, e.g. it's not plain JavaScript.

By default, if Jest sees a Babel config, it will use that to transform your files, ignoring "node_modules".

Here's what you can do:
 • To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
 • If you need a custom transformation specify a "transform" option in your config.
 • If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.

You'll find more details and examples of these config options in the docs:
https://jestjs.io/docs/en/configuration.html

I solved it using @karlhorky suggestion documented in pr #1019, but I would like to know if this problem will be solved.