firebase-js-sdk/repo-scripts/size-analysis/bundle/webpack.ts

/**
 * @license
 * Copyright 2020 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import webpack, { OutputFileSystem } from 'webpack';
// @ts-ignore
import virtualModulesPlugin from 'webpack-virtual-modules';
import { createFsFromVolume, IFs, Volume } from 'memfs';
import path from 'path';
import { projectRoot } from '../util';

/**
 *
 * @param fileContent
 * @param moduleDirectory - the path to the node_modules folder of the temporary project in npm mode.
 *                          undefined in local mode
 */
export async function bundleWithWebpack(
  fileContent: string,
  moduleDirectory?: string
): Promise<string> {
  const entryFileName = '/virtual_path_to_in_memory_file/index.js';
  const outputFileName = 'o.js';

  const resolveConfig: webpack.ResolveOptions = {
    mainFields: ['module', 'main']
  };

  if (moduleDirectory) {
    resolveConfig.modules = [moduleDirectory];
  } else {
    // local mode
    resolveConfig.modules = [`${projectRoot}/node_modules`];
  }

  const compiler = webpack({
    entry: entryFileName,
    output: {
      filename: outputFileName
    },
    resolve: resolveConfig,
    plugins: [
      new virtualModulesPlugin({
        [entryFileName]: fileContent
      })
    ],
    mode: 'production'
  });

  // use virtual file system for output to avoid I/O
  compiler.outputFileSystem = getMemoryFileSystem() as OutputFileSystem;

  return new Promise<string>((res, rej) => {
    compiler.run((err, stats) => {
      if (err) {
        rej(err);
        return;
      }

      // Hack to get string output without reading the output file using an internal API from webpack
      // eslint-disable-next-line @typescript-eslint/no-explicit-any
      res((stats!.compilation.assets[outputFileName] as any)['_value']);
    });
  });
}

function getMemoryFileSystem(): IFs {
  const fs = createFsFromVolume(new Volume());
  // eslint-disable-next-line @typescript-eslint/no-explicit-any
  (fs as any).join = path.join.bind(path);
  return fs;
}