sass-style-template

A simple SCSS watcher with autoprefixer.

Goals

• Use Lit + SASS to build Web Components.
• Leverage ES6 module features to enable easy adoption of import-attributes for CSS module scripts.
• Keep it simple and independent of any bundler such as rollup, parcel, webpack.

// I don't want to use SASS directly in my code
import styles from './my-component-style.scss' 😟

---

Flow

• my-component-styles.scss

:host {
  display: block;
  color: #{'${unsafeCSS(tokens.colors.primary)}'};

  @at-root #{&}([variant=large]) {
    letter-spacing: 3px;
  }
}

p {
  background-color: #{'${unsafeCSS(tokens.colors.secondary)}'};
  :host([variant='large']) & {
    padding: calc(#{'${unsafeCSS(tokens.spaces.xlarge)}'} + 16px);
  }
}

• my-component-styles.css.js

import {css, unsafeCSS} from 'lit';
import * as tokens from 'my-design-system-tokens';

export const styles = css`
  :host {
    display: block;
    color: ${unsafeCSS(tokens.colors.primary)};
  }
  :host([variant='large']) {
    letter-spacing: 3px;
  }

  p {
    background-color: ${unsafeCSS(tokens.colors.secondary)};
  }
  :host([variant='large']) p {
    padding: calc(${unsafeCSS(tokens.spaces.xlarge)} + 16px);
  }
`;

• my-component.js

import {html, LitElement} from 'lit';
import { styles } from './my-component-styles.css.js';

class MyComponent extends LitElement {
  static get styles() {
    return [styles]
  }
}

---

Or just, compile .scss files to .css file and then use CSS module scripts

import {html, LitElement} from 'lit';
import styles from './my-component-styles.css' with { type: 'css' };

class MyComponent extends LitElement {
  static get styles() {
    return [styles]
  }
}

---

How it works

The first time a default template will be used to create a style file

// sass-template.tmpl
import {css} from 'lit';

export const styles = css`<% content %>`;

// my-component.scss
:host {
  display: block;
  color: desaturate(#ad141e, 20%);
}

my-component.scss --> my-component-styles.css.js

or without suffix

my-component.scss --> my-component.css.js

Following changes in the scss file (my-component.scss) will update only the content between the css``; template literal in .css.js file

// from original template
import {css} from 'lit';

// new content added later, it will not be deleted when updating scss file
import * as tokens from 'my-design-system-tokens';

export const styles = css`
  // only this part will be modified
  // new css from scss file
`;

---

Usage

npm i -D sass-style-template

Here is an example of using Vite + concurrently in the package scripts:

// package.json
"scripts": {
  "start": "concurrently -k -r \"npm:sass:watch\" \"npm:vite\"",
  "vite": "vite",
  "sass:watch": "sass-style-template"
}

Options

sass-style-template

// commander options
version(pkg.version, '-v, --version', 'show version number')
  .option('-s, --marker-start <string>', 'start replace position')
  .option('-e, --marker-end <string>', 'end replace position')
  .option('-g, --custom-glob <string>', 'string pattern to be matched')
  .option('-c, --css-file', 'generate a CSS file instead of JS or TS')
  .option('-w, --wo-suffix', 'without suffix string `-styles`')
  .option('-j, --js-file <string>', 'file extension')
  .option('-d, --destination <string>', 'location of the output file')
  .option('-h, --hide-reload', 'no reload info output');

Typescript (--js-file option)

// package.json
"scripts": {
  "start": "concurrently -k -r \"npm:sass:watch\" \"npm:vite\"",
  "vite": "vite",
  "sass:watch": "sass-style-template -j ts"
}

---

Default option value

sass-template.tmpl

import {css}from 'lit';

export const styles = css`<% content %>`;

Custom Template

Creating a custom template file in the root directory with the name sass-template.tmpl

// Example: sass-template.tmpl
// https://github.com/material-components/material-web/blob/main/scripts/css-to-ts.ts

/**
 * @license
 * Copyright 2024 XXX LLC
 * SPDX-License-Identifier: Apache-2.0
 */
import {css} from 'lit';
export const styles = css`<% content %>`;

---

--marker-start (-s)

start replace position : const styles = css`

--marker-end (-e)

end replace position : `; export { styles as default };

--custom-glob (g)

pattern to be matched : ./*.scss, ./src/**/*.scss

--css-file (-c)

generate css file instead of using template : undefined

--wo-suffix (-w)

without suffix string -styles : undefined

--js-file (-j)

file extension : js

--destination (-d)

location of the output file : undefined

--hide-reload (-h)

suppress reload info output : false

---

Example:

Scaffold a new Lit component with SASS using:

npm init @blockquote/wc

Free Software.