purgecss-from-lit

This package is a purgecss extractor for extracting css selectors from typescript files containing lit web components. Specifically, it will parse the html-tagged templates within your source code and extract classes from the HTML within.

Caveats

• This plugin parses all included code as typescript. This shouldn't cause any issues when parsing javascript but there may be code that causes issues.

• This plugin only looks for template literals of the form

  html`<div>HTML here</div>`

  If you end up directly invoking the html function somehow then that will not be caught by purgecss-from-lit.

• Elements, attributes, classes, and ids added as template values will not be picked up. If you find that those selectors are being stripped by purgecss then you will need to add them to the safelist in your purgecss config.

  For example, purgecss-from-lit will not detect the button tag in the element below

  const button = literal`button`;
  const demoClass = "demo-button";
  
  html`<${button} class=${demoClass}>Click Me</button>`

  If you use the button tag nowhere else in your page or app then you would need to add the button selector to the safelist in order to preserve it. The same applies for the .demo-button class here.

Installation

npm

npm install --save-dev @swlynch99/purgecss-from-lit

yarn

yarn install -D @swlynch99/purgecss-from-lit

pnpm

pnpm install -D @swlynch99/purgecss-from-lit

Usage

List the function as one of the extractors in your purgecss config

import purgeLit from '@swlynch99/purgecss-from-lit';

export default {
    extractors: [
        {
            extractor: purgeLit(),
            extensions: ['js', 'ts']
        }
    ],
    ...
}

You can optionally pass a config for @typescript-eslint/typescript-estree in order to configure how the files are parsed. This can be used to generate a lit extractor that supports JSX (although it will not parse classes from said JSX).

import purgeLit from '@swlynch99/purgecss-from-lit';

export default {
    extractors: [
        {
            extractor: purgeLit({ jsx: true }),
            extensions: ['jsx', 'tsx'],
        }
    ]
}