scripts/build/rollup.config.js

// Copyright 2020 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.

// @ts-check

import {defaultStrategy} from 'minify-html-literals/src/strategy';  // eslint-disable-line rulesdir/es_modules_import
import * as path from 'path';
import minifyHTML from 'rollup-plugin-minify-html-template-literals';
import {terser} from 'rollup-plugin-terser';

/**
 * `path.dirname` does not include trailing slashes. If we would always
 * use `path.dirname` and then later perform comparisons on the paths that
 * it returns, we could run into false positives. For example, given the
 * the following two paths:
 *
 *     front_end/timeline_model/TimelineModel.js
 *     front_end/timeline/Timeline.js
 *
 * And that would have the following values for `path.dirname`:
 *
 *     front_end/timeline_model
 *     front_end/timeline
 *
 * If we would do a simple `.startswith` on the `path.dirname` of both of
 * these paths, then the first path would start with the dirname of the
 * second. However, they *are* part of different folders. To fix that problem,
 * we need to force a path separator after each folder. That makes sure we
 * and up with the following comparison of path dirnames:
 *
 *     front_end/timeline_model/
 *     front_end/timeline/
 *
 * Now, the first path does *not* start with the second one, as expected.
 *
 * @param {string} file
 * @return {string}
 */
function dirnameWithSeparator(file) {
  return path.dirname(file) + path.sep;
}

/**
 * @type {import("minify-html-literals").Strategy<import("html-minifier").Options, unknown>}
 */
const minifyHTMLStrategy = {
  getPlaceholder() {
    return 'TEMPLATE_EXPRESSION';
  },
  combineHTMLStrings(parts, placeholder) {
    return defaultStrategy.combineHTMLStrings(parts, placeholder);
  },
  minifyHTML(html, options) {
    return defaultStrategy.minifyHTML(html, options);
  },
  minifyCSS(css, options) {
    return defaultStrategy.minifyCSS(css, options);
  },
  splitHTMLByPlaceholder(html, placeholder) {
    return defaultStrategy.splitHTMLByPlaceholder(html, placeholder);
  }
};

/** @type {function({configDCHECK: boolean}): import("rollup").MergedRollupOptions} */
// eslint-disable-next-line import/no-default-export
export default commandLineArgs => ({
  treeshake: false,
  context: 'self',
  output: [{
    format: 'esm',
  }],
  plugins: [
    minifyHTML({
      options: {
        strategy: minifyHTMLStrategy,
        minifyOptions: {
          collapseInlineTagWhitespace: false,
          collapseWhitespace: true,
          conservativeCollapse: true,
          minifyCSS: false,
          removeOptionalTags: true,
        },
      },
    }),
    terser({
      compress: {
        pure_funcs: commandLineArgs.configDCHECK ? ['Platform.DCHECK'] : [],
      },
    }),
    {
      name: 'devtools-plugin',
      resolveId(source, importer) {
        if (!importer) {
          return null;
        }
        const currentDirectory = path.normalize(dirnameWithSeparator(importer));
        const importedFilelocation = path.normalize(path.join(currentDirectory, source));
        const importedFileDirectory = dirnameWithSeparator(importedFilelocation);

        // Generated files are part of other directories, as they are only imported once
        if (path.basename(importedFileDirectory) === 'generated') {
          return null;
        }

        // An import is considered external (and therefore a separate
        // bundle) if its filename matches its immediate parent's folder
        // name (without the extension). For example:
        // import * as Components from './components/components.js' = external
        // import * as UI from '../ui/ui.js' = external
        // import * as LitHtml from '../third_party/lit-html/lit-html.js' = external
        // import {DataGrid} from './components/DataGrid.js' = not external
        // import * as Components from './components/foo.js' = not external

        // Note that we can't do a simple check for only `third_party`, as in Chromium
        // our full path is `third_party/devtools-frontend/src/`, which thus *always*
        // includes third_party. It also not possible to use the current directory
        // as a check for the import, as the import will be different in Chromium and
        // would therefore not match the path of `__dirname`.
        // These should be removed because the new heuristic _should_ deal with these
        // e.g. it'll pick up third_party/lit-html/lit-html.js is its own entrypoint

        // Puppeteer has dynamic imports in its build gated on an ifNode
        // flag, but our Rollup config doesn't know about that and tries
        // to parse dynamic import('fs'). Let's ignore Puppeteer for now.
        // The long term plan is probably for Puppeteer to ship a web
        // bundle anyway. See go/pptr-agnostify for details.
        if (importedFileDirectory.includes(path.join('front_end', 'third_party', 'puppeteer'))) {
          return null;
        }

        // The CodeMirror addons look like bundles (addon/comment/comment.js) but are not.
        if (importedFileDirectory.includes(path.join('front_end', 'third_party', 'codemirror', 'package'))) {
          return null;
        }

        // The LightHouse bundle shouldn't be processed by `terser` again, as it is uniquely built
        if (importedFilelocation.includes(
                path.join('front_end', 'third_party', 'lighthouse', 'lighthouse-dt-bundle.js'))) {
          return {
            id: importedFilelocation,
            external: true,
          };
        }

        const importedFileName = path.basename(importedFilelocation, '.js');
        const importedFileParentDirectory = path.basename(path.dirname(importedFilelocation));
        const isExternal = importedFileName === importedFileParentDirectory;

        return {
          id: importedFilelocation,
          external: isExternal,
        };
      }
    },
  ]
});