CSS Modules: Scope Locals & Extend

Transforms:

:local(.continueButton) {
  color: green;
}

into:

:export {
  continueButton: __buttons_continueButton_djd347adcxz9;
}
.__buttons_continueButton_djd347adcxz9 {
  color: green;
}

so it doesn't pollute CSS global scope and can be simply used in JS like so:

import styles from './buttons.css'
elem.innerHTML = `<button class="${styles.continueButton}">Continue</button>`

Composition

Since we're exporting class names, there's no reason to export only one. This can give us some really useful reuse of styles:

.globalButtonStyle {
  background: white;
  border: 1px solid;
  border-radius: 0.25rem;
}
.globalButtonStyle:hover {
  box-shadow: 0 0 4px -2px;
}
:local(.continueButton) {
  compose-with: globalButtonStyle;
  color: green;
}

becomes:

.globalButtonStyle {
  background: white;
  border: 1px solid;
  border-radius: 0.25rem;
}
.globalButtonStyle:hover {
  box-shadow: 0 0 4px -2px;
}
:local(.continueButton) {
  compose-with: globalButtonStyle;
  color: green;
}