Errors when using jest and jsdom

[anomiex]

When running tests using jest and jest-environment-jsdom, version 1.1.2 of this package causes a failure:

 FAIL  ./test.js
  ● 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:

    /tmp/test/node_modules/parsel-js/dist/parsel.js:392
    export { RECURSIVE_PSEUDO_CLASSES, RECURSIVE_PSEUDO_CLASSES_ARGS, TOKENS, TRIM_TOKENS, flatten, gobbleParens, parse, specificity, specificityToNumber, stringify, tokenize, tokenizeBy, walk };
    ^^^^^^

    SyntaxError: Unexpected token 'export'

      3 |  */
      4 |
    > 5 | const parselJs = require( 'parsel-js' );
        |                  ^
      6 |
      7 | test( 'it works', () => {
      8 |     const element = document.createElement('div');

      at Runtime.createScriptFromCode (node_modules/jest-runtime/build/index.js:1505:14)
      at Object.require (test.js:5:18)

Test Suites: 1 failed, 1 total
Tests:       0 total
Snapshots:   0 total
Time:        0.381 s

The problem is that, with jest-environment-jsdom, the conditions available are "browser", "require" (not "import"), and "default", but parsel-js's exports assumes "browser" always comes with "import".

A detailed analysis of a similar problem in another package, along with potential workarounds, may be found at microsoft/accessibility-insights-web#5421 (comment).

Reproduction

1. Create an empty directory for the test.
2. Run npm add jest jest-environment-jsdom parsel-js
3. Create the following file named test.js:

   /**
    * @jest-environment jsdom
    */
   
   const parselJs = require( 'parsel-js' );
   
   test( 'it works', () => {
       const element = document.createElement('div');
       expect( element ).not.toBeNull();
   } );

4. Run npm exec jest test.js
5. See error

Comments

The problem lies in this code:

parsel/package.json

Lines 9 to 17 in ff2e34f

	"exports": {
	".": {
	"browser": "./dist/parsel.js",
	"import": "./dist/parsel.min.js",
	"require": "./dist/parsel.min.cjs",
	"types": "./dist/parsel.d.ts",
	"umd": "./dist/umd/parsel.min.js"
	}
	},

One possible fix would be to move "browser" down in the list, so "require" and "import" come before it. In that case it'll only be used when something specifies "browser" without either "require" or "import".

Another possible fix, if you really want different code for browser environments versus other environments, would be to do "browser" something like this:

"browser": {
    "import": "./dist/parsel.js",
    "require": "./dist/parsel.cjs",
    "default": "./dist/parsel.js",
}

P.S. You may also want to move "types" up to the top of the list, so TypeScript finds it before the generic "import" and "require".