SWC with JavaScript: How to handle CSS imports and how to absolute imports?

TL;DR

• How can you tell SWC to compile CSS files imported in React components?
• How can you tell SWC to compile absolute imports in tests and in React components?

---

Context

We’re migrating from Babel to SWC. (I asked a question a little while ago. I’m improving on that question’s answer.)

We’re migrated the command from:

"test": "NODE_ENV=test riteway -r @babel/register 'src/**/*.test.js' | tap-nirvana",

to

"test": "SWC_NODE_PROJECT=./jsconfig.json riteway -r @swc-node/register src/**/*.test.js | tap-nirvana",

where the jsconfig.json looks like this:

{
  "compilerOptions": {
    "allowJs": true,
    "baseUrl": "./src",
    "jsx": "react-jsx"
  }
}

If we write try to compile a test for a self-contained component (no absolute imports, no CSS) it works:

import { describe } from 'riteway';
import render from 'riteway/render-component';

function HomePageComponent({ user: { email } }) {
  return <p>{email}</p>;
}

describe('home page component', async assert => {
  const user = { email: 'foo' };
  const $ = render(<HomePageComponent user={user} />);

  assert({
    given: 'a user',
    should: 'render its email',
    actual: $('p').text(),
    expected: user.email,
  });
});

The test compiles fine.

With Babel we had a .babelrc like this:

{
  "env": {
    "test": {
      "plugins": [
        [
          "module-resolver",
          {
            "root": [
              "."
            ],
            "alias": {
              "components": "./src/components",
              "config": "./src/config",
              "features": "./src/features",
              "hocs": "./src/hocs",
              "hooks": "./src/hooks",
              "pages": "./src/pages",
              "redux": "./src/redux",
              "styles": "./src/styles",
              "tests": "./src/tests",
              "utils": "./src/utils"
            }
          }
        ]
      ]
    }
  },
  "presets": [
    [
      "next/babel",
      {
        "ramda": {}
      }
    ]
  ],
  "plugins": [
    ["styled-components", { "ssr": true }]
  ]
}

Where the styles where taken care of by styled-components and the absolute imports where defined via the module-resolver plugin. (We switched away from styled-components to CSS modules, which is why we import from .module.css CSS files. Anyways …)

If we write the test how we wanted to write it with their actual imports like this:

import { describe } from 'riteway';
import render from 'riteway/render-component';
import { createPopulatedUserProfile } from 'user-profile/user-profile-factories';

import HomePageComponent from './home-page-component';

describe('home page component', async assert => {
  const user = createPopulatedUserProfile();
  const $ = render(<HomePageComponent user={user} />);

  assert({
    given: 'a user',
    should: 'render its email',
    actual: $('p').text(),
    expected: user.email,
  });
});

It fails with:

$ SWC_NODE_PROJECT=./jsconfig.json riteway -r @swc-node/register src/features/home/home-page-component.test.js | tap-nirvana
/Users/janhesters/dev/my-project/src/features/home/home.module.css:1
(function (exports, require, module, __filename, __dirname) { .container {
                                                              ^

SyntaxError: Unexpected token '.'

when we leave in the CSS import in home-page-component.js, or with:

$ SWC_NODE_PROJECT=./jsconfig.json riteway -r @swc-node/register src/features/home/home-page-component.test.js | tap-nirvana
node:internal/modules/cjs/loader:936
  throw err;
  ^

Error: Cannot find module 'user-profile/user-profile-factories'
Require stack:
- /Users/janhesters/dev/my-project/src/features/home/home-page-component.test.js
- /Users/janhesters/dev/my-project/node_modules/riteway/bin/riteway

respectively, when we get rid of the CSS import.

How can we help SWC understand CSS (or mock CSS modules) and how can we help it understand absolute imports?

We already set the baseUrl in jsconfig.json …