systrace/catapult/common/node_runner/node_runner/minify

#!/usr/bin/env node
'use strict';
/*
Copyright 2018 The Chromium Authors. All rights reserved.
Use of this source code is governed by a BSD-style license that can be
found in the LICENSE file.

This script wraps common HTML transformations including stripping whitespace and
comments from HTML, CSS, and Javascript.
*/
const dom5 = require('dom5');
const escodegen = require('escodegen');
const espree = require('espree');
const fs = require('fs');
const nopt = require('nopt');

const args = nopt();
const filename = args.argv.remain[0];

let html = fs.readFileSync(filename).toString('utf8');
let parsedHtml = dom5.parse(html);
// First, collapse text nodes around comments (by removing comment nodes,
// re-serializing, and re-parsing) in order to prevent multiple extraneous
// newlines.
for (const node of dom5.nodeWalkAll(parsedHtml, () => true)) {
  if (dom5.isCommentNode(node)) {
    dom5.remove(node);
  }
}
html = dom5.serialize(parsedHtml);
parsedHtml = dom5.parse(html);
// Some of these transformations are based on polyclean:
// https://github.com/googlearchive/polyclean
for (const node of dom5.nodeWalkAll(parsedHtml, () => true)) {
  if (dom5.isTextNode(node)) {
    dom5.setTextContent(node, dom5.getTextContent(node)
      .replace(/ *\n+ */g, '\n')
      .replace(/\n+/g, '\n'));
  } else if (dom5.predicates.hasTagName('script')(node) &&
             !dom5.predicates.hasAttr('src')(node)) {
    let text = dom5.getTextContent(node);
    const ast = espree.parse(text, {ecmaVersion: 2018});
    text = escodegen.generate(ast, {format: {indent: {style: ''}}});
    dom5.setTextContent(node, text);
  } else if (dom5.predicates.hasTagName('style')(node)) {
    dom5.setTextContent(node, dom5.getTextContent(node)
      .replace(/[\r\n]/g, '')
      .replace(/ {2,}/g, ' ')
      .replace(/(^|[;,\:\{\}]) /g, '$1')
      .replace(/ ($|[;,\{\}])/g, '$1'));
  }
}
fs.writeFileSync(filename, dom5.serialize(parsedHtml));