karma.webpack.js

/*
 * Copyright The OpenTelemetry Authors
 * SPDX-License-Identifier: Apache-2.0
 */

const path = require('path');
const webpack = require('webpack')

// This is the webpack configuration for browser Karma tests with coverage.
module.exports = {
  mode: 'development',
  target: 'web',
  output: {filename: 'bundle.js'},
  resolve: {
    extensions: ['.ts', '.js'],
    fallback: {
      // Enable the assert library polyfill because that is used in tests
      "assert": require.resolve('assert/'),
      "util": require.resolve('util/'),
      // Only node-only platform code uses `path`; browser code paths never reach
      // it. If that breaks: `TypeError: path.normalize is not a function`.
      "path": false,
    },
  },
  devtool: 'eval-source-map',
  plugins: [
    new webpack.ProvidePlugin({
      // Not a global: only modules with a free `process` (such as util) get
      // it. Absolute, since isolated installs hide `process` from those modules.
      process: require.resolve('process/browser.js')
    }),
    // Benchmark.js checks for AMD's define function which doesn't exist in webpack.
    // NOTE: This pollutes tests with a defined 'self.define' global.
    new webpack.BannerPlugin({
      banner: 'self.define = self.define || Object.assign(function(){}, {amd: false});',
      raw: true
    })
  ],
  module: {
    rules: [
      {
        // #platform resolves to src for the package under test only; dependencies
        // keep their dist, as a global condition would resolve them to their src too.
        include: path.resolve('src'),
        resolve: { conditionNames: ['otel', '...'] },
      },
      {
        test: /\.ts$/,
        // transpileOnly: tsconfig.base.json sets `composite` but we never run
        // `tsc -b`, so no `.tsbuildinfo` exists; ts-loader's default mode wants one.
        use: { loader: 'ts-loader', options: { transpileOnly: true } },
      },
      {
        test: /\.js$/,
        exclude: {
          and: [/node_modules/], // Exclude libraries in node_modules ...
          not: [
            // Except for a few of them that needs to be transpiled because they use modern syntax
            /zone.js/,
          ],
        },
        use: {
          loader: 'babel-loader',
          options: {
            presets: ['@babel/preset-env'],
          }
        },
      },
      {
        enforce: 'post',
        exclude: /(node_modules|\.test\.[tj]sx?$)/,
        test: /\.ts$/,
        use: {
          loader: 'babel-loader',
          options: {
            plugins: ['babel-plugin-istanbul'],
          }
        },
      },
    ],
  },
};