Cannot use import statement outside a module

[Hugh Gallagher]

Hello,

I'm using Jest to test my Stimulus controllers. However, since introducing stimulus-use, I am encountering an error that indicates Jest is unable to recognise stimulus-use as an ESM module (see below). I appreciate this sounds more like a Jest/Node problem, but it is possibly due to the absence of a type: module declaration in the root of the projects package.json.

{
  "type": "module",
   // ...
}

I've tried the various solutions from Jest in the output below without much luck, so just wanted to confirm if stimulus-use should be declaring itself as a module or not?

Thanks

---

See https://jestjs.io/docs/ecmascript-modules

Beyond that, we attempt to follow node's logic for activating "ESM mode" (such as looking at type in package.json or .mjs files), see their docs for details.

$ yarn node --experimental-vm-modules --no-warnings $(yarn bin jest)

Test suite failed to run

    Jest encountered an unexpected token

    Jest failed to parse a file. This happens e.g. when your code or its dependencies use non-standard JavaScript syntax, or when Jest is not configured to support such syntax.

    Out of the box Jest supports Babel, which will be used to transform your files into valid JS based on your Babel configuration.

    By default "node_modules" folder is ignored by transformers.

    Here's what you can do:
     • If you are trying to use ECMAScript Modules, see https://jestjs.io/docs/ecmascript-modules for how to enable it.
     • If you are trying to use TypeScript, see https://jestjs.io/docs/getting-started#using-typescript
     • 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/configuration
    For information about custom transformations, see:
    https://jestjs.io/docs/code-transformation

    Details:

    /Users/user-name/project-name/node_modules/stimulus-use/dist/index.js:4
    import { Controller } from "@hotwired/stimulus";
    ^^^^^^

    SyntaxError: Cannot use import statement outside a module

      at Runtime.createScriptFromCode (node_modules/jest-runtime/build/index.js:1505:14)

[Hugh Gallagher]

It sounds like this is a generic ESM issue people run into with Jest. For now, I seem to have got something working by setting a transformer (we use esbuild already, so aligned with that) and setting stimulus-use not to be transformed.

"jest": {
  "transform": {
    "^.+\\.js$": "esbuild-jest"
  },
  "transformIgnorePatterns": [
      "node_modules/(?!(stimulus-use)/)"
  ],
  // ...
},