Develop Reference

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?
Here is a minimal reproducible example.
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 ...

About absolute path
You already add baseUrl in the jsconfig.json file but didn't add the paths, you should modify your config file like mine:
{
"compilerOptions": {
"baseUrl": "./src",
"paths": {
"#screens": ["./screens"],
"#shared": ["./shared"],
"#shared/*": ["./shared/*"]
},
The paths are the alias of module-resolver, and I guess your root shouldn't be ".", it should be exactly like your jsconfig.json file, I mean the baseUrl value.
"plugins": [
[
"module-resolver",
{
"root": ["./src"],
"extensions": [".ts", ".tsx", ".js", ".jsx", ".json"],
"alias": {
"#screens": "./src/screens",
"#shared": "./src/shared"
}
}
]
],
If you have Webpack, you should have alias config in your resolve key off Webpack config object, like mine:
const resolve = {
extensions: ['.js', '.jsx', '.ts', '.tsx', '.json'],
alias: {
'#screens': path.join(__dirname, 'src/screens/'),
'#shared': path.join(__dirname, 'src/shared/'),
},
modules: ['src', 'node_modules'],
descriptionFiles: ['package.json'],
};
About CSS
Actually, you are using CSS file as CSS-Modules not like recommended NexJS doc, in docs developer should import CSS like import './styles.css' and then use it as string in JSX like <div className="main"
But
You are importing it like a module (CSS-Module):
// you did it
import styles from './styles.css';
<div className={styles.main}
As you know it is built-in support by this doc, it is supported by NextJS, but SWC cannot understand it. I put in hours to find a way for it, but it seems SWC doesn't support CSS-Module yet. you should create your own plugin for SWC to support CSS-Module.

How can we help SWC understand CSS (or mock CSS modules)? - SWC doesn't understand css natively, and neither did Babel. As you noted, when you were using Babel, the plugin styled-components took care of this. You'll need to do the same with SWC. I can't find an existing SWC plugin that does this, but you can roll your own. Obviously this is a pain, but such is the cost of using new tooling.
How can we help SWC understand absolute imports? - The .swrc options for baseUrl and paths should do what you want, but that, too, seems to have some issues.
You may have better luck creating issues directly in the #swc-node GitHub repo, but given the comments there it feels like you might be SOL for a while. Might be faster/easier to rewrite your tests using one of the libraries that Next supports out of the box.

I was able to solve all issues without writing any plugins. I pushed the solution to my example repo from the question.
Firstly, use the official SWC project's register. This means, you have to compile your tests like this:
"test": "riteway -r #swc/register 'src/**/*.test.js' | tap-nirvana",
You can install it by running:
yarn add --dev #swc/core #swc/register
We need this version of register, because it takes into account an .swcrc file, which the other one did not.
Secondly, you need both "path" and "baseUrl" to fix the absolute imports because for some reason SWC doesn't infer all paths with only a "baseUrl" provided. And you need to adapt your .swcrc to handle React.
{
"jsc": {
"baseUrl": "./src",
"paths": {
"*.css": ["utils/identity-object-proxy.js"],
"utils/*": ["utils/*"]
},
"parser": {
"jsx": true,
"syntax": "ecmascript"
},
"transform": {
"react": {
"runtime": "automatic"
}
}
},
"module": {
"type": "commonjs"
}
}
Thirdly, to solve .css you need to remap all imports to .css files to an identity object proxy, which you can see in the .swcrc example above. An identity object proxy is an object that, when you reference any property, returns the stringified key that you're trying to reference. You can create one yourself like this:
const identityObjectProxy = new Proxy(
{},
{
get: function getter(target, key) {
if (key === '__esModule') {
return false;
}
return key;
},
},
);
export default identityObjectProxy;
For the .css remap to go into effect you need to make all your imports to .css files absolute imports. (import styles from './styles.module.css won't work!)

How to include monorepo packages in Cypress code coverage

I have multi packages in monorepo.
/pkg1
/pkg2
/pkg3
- react-app
- cypress
- src
- package.json
I am using #cypress/instrument-cra to collect coverage and it works only to cover the code inside react-app.
I need to go further because react-app is actually just a playground while the src has to be covered along with other packages that are used inside the react-app. I am importing packages as following:
import pkg1 from #myProject/pkg1
How can I use code coverage for pkg1?
I tried to config nyc but it didn't work
"nyc": {
"all": true,
"include": [
"node_modules"
],
"excludeNodeModules": false
}
Thanks!

Create .nycrc file in your root folder and:
{
"all": true,
"include": [
"pkg1/src/**"
],
"exclude": [
"**/test/**"
],
}

How Should VSCode Be Configured To Support A Lerna Monorepo?

I have a lerna monorepo containing lots of packages.
I'm trying to achieve the following:
Ensure that VSCode provides the correct import suggestions (based on package names, not on relative paths) from one package to another.
Ensure that I can 'Open Definition' of one of these imports and be taken to the src of that file.
For 1. I mean that if I am navigating code within package-a and I start to type a function exported by package-b, I get a suggestion that will trigger the adding of an import: `import { example } from 'package-b'.
For 2. I mean that if I alt/click on the name of a function exported by 'package-b' while navigating the file from a different package that has imported it, I am taken to '/packages/namespace/package/b/src/file-that-contains-function.js',
My (lerna) monorepo is structured as standard, for example here is a 'components' package that is published as #namespace/components.
- packages
- components
- package.json
- node_modules
- src
- index.js
- components
- Button
- index.js
- Button.js
- es
- index.js
- components
- Button
- index.js
- Button.js
Note that each component is represented by a directory so that it can contain other components if necessary. In this example, packages/components/index exports Button as a named export. Files are transpiled to the package's /es/ directory.
By default, VSCode provides autosuggestions for imports, but it is confused by this structure and, for if a different package in the monorepo needs to use Button for example, will autosuggest all of the following import paths:
packages/components/src/index.js
packages/components/src/Button/index.js
packages/components/src/Button/Button.js
packages/components/es/index.js
packages/components/es/Button/index.js
packages/components/es/Button/Button.js
However none of these are the appropriate, because they will be rendered as relative paths from the importing file to the imported file. In this case, the following import is the correct import:
import { Button } from '#namespace/components'
Adding excludes to the project's jsconfig.json has no effect on the suggested paths, and doesn't even remove the suggestions at /es/*:
{
"compilerOptions": {
"target": "es6",
},
"exclude": [
"**/dist/*",
"**/coverage/*",
"**/lib/*",
"**/public/*",
"**/es/*"
]
}
Explicitly adding paths using the "compilerOptions" also fails to set up the correct relationship between the files:
{
"compilerOptions": {
"target": "es6",
"baseUrl": ".",
"paths": {
"#namespace/components/*": [
"./packages/namespace-components/src/*.js"
]
}
},
}
At present Cmd/Clicking on an import from a different package fails to open anything (no definition is found).
How should I configure VSCode so that:
VSCode autosuggests imports from other packages in the monorepo using the namespaced package as the import value.
Using 'Open Definition' takes me to the src of that file.
As requested, I have a single babel config in the root:
const { extendBabelConfig } = require(`./packages/example/src`)
const config = extendBabelConfig({
// Allow local .babelrc.js files to be loaded first as overrides
babelrcRoots: [`packages/*`],
})
module.exports = config
Which extends:
const presets = [
[
`#babel/preset-env`,
{
loose: true,
modules: false,
useBuiltIns: `entry`,
shippedProposals: true,
targets: {
browsers: [`>0.25%`, `not dead`],
},
},
],
[
`#babel/preset-react`,
{
useBuiltIns: true,
modules: false,
pragma: `React.createElement`,
},
],
]
const plugins = [
`#babel/plugin-transform-object-assign`,
[
`babel-plugin-styled-components`,
{
displayName: true,
},
],
[
`#babel/plugin-proposal-class-properties`,
{
loose: true,
},
],
`#babel/plugin-syntax-dynamic-import`,
[
`#babel/plugin-transform-runtime`,
{
helpers: true,
regenerator: true,
},
],
]
// By default we build without transpiling modules so that Webpack can perform
// tree shaking. However Jest cannot handle ES6 imports becuase it runs on
// babel, so we need to transpile imports when running with jest.
if (process.env.UNDER_TEST === `1`) {
// eslint-disable-next-line no-console
console.log(`Running under test, so transpiling imports`)
plugins.push(`#babel/plugin-transform-modules-commonjs`)
}
const config = {
presets,
plugins,
}
module.exports = config

In your case, I would make use of lerna in combination with yarn workspaces.
When running yarn install, all your packages are linked under your #namespace in a global node_modules folder. With that, you get IntelliSense.
I've set up an example repository here: https://github.com/flolude/stackoverflow-lerna-monorepo-vscode-intellisense
You just need to add "useWorkspaces": "true" to your lerna.json
lerna.json
{
"packages": ["packages/*"],
"version": "0.0.0",
"useWorkspaces": "true"
}
And the rest is just propper naming:
global package.json
{
"name": "namespace",
// ...
}
package.json of your component package
{
"name": "#namespace/components",
"main": "src/index.js",
// ...
}
package.json of the package that imports the components
{
"name": "#namespace/components",
"main": "src/index.js",
"dependencies": {
"#namespace/components":"0.0.0"
}
// ...
}
Then you can do the following:
import { Component1 } from '#namespace/components';
// your logic
Automatically Importing from #namespace
Unfortunately, I couldn't find a way to make this work in VSCode with a Javascript Monorepo. But there are some things you can do:
Use Typescript (tutorial, other tutorial)
Use module-alias
Add import {} from '#namespace/components' to the top of your file
Use Auto Import Extension

Edit: This is broken with the latest version of VSCode.
I finally managed to get this working reliably. You need to create a separate jsconfig.js for every package in your monorepo, for example:
{monorepo root}/packages/some-package/jsconfig.json:
{
"compilerOptions": {
"target": "es6",
"jsx": "preserve",
"module": "commonjs"
},
"include": ["src/**/*.js"],
"exclude": ["src/index.js"]
}
Note that I've excluded the src/index.js file so it doesn't get offered as an import suggestion from within that package.
This setup appears to achieve:
Intellisense import suggestions from packages instead of using relative paths.
Go to definition to source of other packages in the monorepo.
VSCode has been pretty flaky of late, but it seems to be working.
Note this is working for a JavaScript-only monorepo (not Typescript).

CSS module #import fails the Jest test suit

I am using Jest and Enzyme to test my application. I am getting error:
FAIL app/containers/Navbar/NavbarContainer.test.js
● Test suite failed to run
app/components/Navbar/styles.css: Unexpected token (1:0)
> 1 | #import "../../styles/base/_variables";
| ^
2 |
3 | .navbar{
4 | width: $navbar-width;
This is my Jest configuration in package.json:
"jest": {
"verbose": true,
"globals": {
"env": {
"isProd": false,
"isDev": true,
"command": "start"
}
},
"moduleNameMapper": {
"\\.(css)$": "identity-obj-proxy"
},
"moduleFileExtensions": [
"js",
"jsx",
"json",
"css"
],
"modulePaths": [
"/app"
],
"moduleDirectories": [
"node_modules"
],
"verbose": true,
"setupFiles": [
"./setupJest.js"
],
"setupTestFrameworkScriptFile": "<rootDir>/setupTests.js"
}
I was following the guides while setting up the application, and I found that identity-obj-proxy will help to mock css-modules functionality, but that's not working in my case. Please let me know what am I missing here.
P.S. this is about not ES6 modules import. The suit failed because there is a #import in css.

UPDATE who use create-react-app from feb 2018.
You cannot override the moduleNameMapper in package.json but in jest.config.js it works, unfortunately i havent found any docs about why it does the trick.
So my jest.config.js look like this:
module.exports = {
...,
"moduleNameMapper": {
"\\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$": "<rootDir>/__mocks__/fileMock.js",
"\\.(scss|sass|css)$": "identity-obj-proxy"
}
}
and it skips scss files and #import quite well.
I added to devDependencies identity-obj-proxy
Backing my answer i followed jest webpack

So, I've found the solution to this problem. I was importing CSS without the extension in my components and Jest was confusing that import with JS file. Solution is instead of importing css like:
import * as styles from './styles'
you should import it like:
import * as styles from './styles.css'

One quick gotcha that I found with this. If you have a jest.config.js file, then you need to set your moduleNameWrapper inside of that config file.

I know this post is old but i solved this issue by adding jest-transform-css as a devDependency
npm i --save-dev jest-transform-css
and then adding the following inside jest.config.js
transform: {
'^.+\\.js$': 'babel-jest',
'.+\\.(css|styl|less|sass|scss)$': 'jest-transform-css'
}
you can refer to this github issue for more information

Jest configuration

I'm adding Jest Testing framework to my React Native project. I'm getting the following error:
Failed to get mock metadata: /Users/me/Documents/Development/project/node_modules/global/window.js
My test file looks like this:
import 'react-native'
import React from 'react'
import { MyComponent } from '../components/MyComponent'
import renderer from 'react-test-renderer'
it('renders correctly', () => {
const tree = renderer.create(<MyComponent />).toJSON()
expect(tree).toMatchSnapshot()
})
And also the Jest configuration in my package.json:
"jest": {
"preset": "jest-react-native",
"testPathIgnorePatterns": ["/node_modules/", "/example/", "/lib/"],
"testRegex": "(/tests/.*|\\.(test|spec))\\.(js|jsx)$",
"automock": "true",
"unmockedModulePathPatterns": [ "lodash" ],
"transformIgnorePatterns": [
"node_modules/(?!#exponent/ex-navigation",
")"
]
}
I had a look over http://facebook.github.io/jest/docs/manual-mocks.html#content as suggested on the error prompted.

I think something is wrong with your jest configuration in package.json.
Here is a sample jest config snippet:
"jest": {
"preset": "react-native",
"cacheDirectory": "./cache",
"coveragePathIgnorePatterns": [
"./app/utils/vendor"
],
"coverageThreshold": {
"global": {
"statements": 80
}
},
"transformIgnorePatterns": [
"/node_modules/(?!react-native|react-clone-referenced-element|react-navigation)"
]
}
preset: The preset is a node environment that mimics the environment of a React Native app. Because it doesn’t load any DOM or browser APIs, it greatly improves Jest’s startup time.
cacheDirectory: It helps you greatly improve the test speed. It does so by creating cache of compiled modules so that next time it doesn’t have to compile the node_modules while running tests.
coveragePathIgnorePatterns: Define the files which want to skip for coverage reports.
coverageThreshold: Defines the threshold limit for all the tests to pass. If the coverage is less than the defined limit, the tests would fail. This helped us to keep a good amount of coverage at all point of time.
transformIgnorePatterns: We pass all the NPM modules here which needs to be transpiled. These modules are basically ES6/7 modules.
PS: I have written a blog on how to setup jest for react-native project. Here is the URL : http://rahulgaba.com/react-native/2017/05/19/Jest-test-suite-with-superpowers.html

Set "automock": "false" in your package.json (automocking with the jest-react-native preset isn't supported)