src/third_party/devtools/scripts/unused_css/index.js

const fs = require('fs');
const path = require('path');
const css = require('css');
const cssWhat = require('css-what');
const acorn = require('acorn');

const utils = require('../utils');
const promisify = require('util').promisify;
const readFile = promisify(fs.readFile);
const FRONTEND_PATH = path.join(__dirname, '..', '..', 'front_end');

const classes = new Set();
const strings = new Set();
const trickyStrings = new Set([
  'crc-node__tree-hostname',
  'tooltip-boundary',
  'terminal',
  'terminal-cursor',
  'composition-view'
]);
(async function() {
  await Promise.all(fs.readdirSync(FRONTEND_PATH).map(dir => processFolder(dir)));
  const unused = [];
  for (const className of classes) {
    if (strings.has(className) || trickyStrings.has(className))
      continue;
    if (className.startsWith('CodeMirror'))
      continue;
    if (className.startsWith('xterm-'))
      continue;
    if (className.startsWith('lh-'))
      continue;
    if (className.startsWith('cm-'))
      continue;
    if (className.startsWith('navigator-'))
      continue;
    if (className.startsWith('object-value-'))
      continue;
    if (className.startsWith('security-summary-'))
      continue;
    if (className.startsWith('security-explanation-title-'))
      continue;
    if (className.startsWith('security-explanation-'))
      continue;
    if (className.startsWith('lock-icon-'))
      continue;
    if (className.startsWith('security-property-'))
      continue;
    if (className.startsWith('url-scheme-'))
      continue;
    if (className.startsWith('infobar-'))
      continue;
    if (className.startsWith('shadow-root-depth-'))
      continue;
    if (className.startsWith('timeline-overview-'))
      continue;
    if (className.startsWith('spritesheet-'))
      continue;
    if (className.startsWith('report-icon--'))
      continue;

    if (checkSuffix('-start'))
      continue;
    if (checkSuffix('-end'))
      continue;
    if (checkSuffix('-column'))
      continue;
    if (checkSuffix('-overview-grid'))
      continue;
    if (checkSuffix('-overview-container'))
      continue;
    if (checkSuffix('-icon'))
      continue;
    unused.push(className);

    function checkSuffix(suffix) {
      return className.endsWith(suffix) && strings.has(className.substring(0, className.length - suffix.length));
    }
  }
  console.log(unused);
  console.log(unused.length);
})();


async function processFolder(dir) {
  if (!utils.isDir(path.join(FRONTEND_PATH, dir)))
    return;
  const modulePath = path.join(FRONTEND_PATH, dir, 'module.json');
  if (!utils.isFile(modulePath))
    return;
  const content = JSON.parse(await readFile(modulePath, 'utf8'));
  const promises = [];
  for (const resource of content.resources || []) {
    if (!resource.endsWith('.css'))
      continue;
    promises.push(processCSSFile(path.join(FRONTEND_PATH, dir, resource)));
  }
  const skips = new Set(content.skip_compilation || []);
  for (const script of content.scripts || []) {
    if (skips.has(script))
      continue;
    promises.push(processScriptFile(path.join(FRONTEND_PATH, dir, script)));
  }
  await Promise.all(promises);
}

async function processCSSFile(cssFile) {
  const content = await readFile(cssFile, 'utf8');
  try {
    const ast = css.parse(content);
    for (const rule of ast.stylesheet.rules) {
      for (const selector of rule.selectors || []) {
        for (const token of parseSimpleSelector(selector)) {
          if (token.name === 'class' || token.name === 'id')
            classes.add(token.value);
        }
      }
    }
  } catch(e) {
    console.log(cssFile, e)
  }
}

function parseSimpleSelector(selector) {
  // css-what isn't the best. Try catch.
  try {
    const parsed = cssWhat(selector)
    return parsed[0] || [];
  } catch(e) {
    return [];
  }
}

async function processScriptFile(scriptFile) {
  const content = await readFile(scriptFile, 'utf8');
  const tokens = acorn.tokenizer(content);
  for (const token of tokens) {
    if(token.type.label === 'string' || token.type.label === 'template') {
      for (const word of token.value.split(' '))
        strings.add(word);
      const regex = /class\s*=\s*['"]?([\w\-_ ]*)/ig;
      let result;
      while ((result = regex.exec(token.value))) {
        for (const word of result[1].split(' '))
          strings.add(word);
      }
    }
  }
}