index.js

module.exports = (
  api,
  options = {
    jsx: true,
  },
) => {
  // https://babeljs.io/docs/en/babel-preset-env
  let envOptions = {
    targets: options.targets || {
      esmodules: true
    },
    spec: options.spec,
    loose: options.loose || false,
    modules: options.modules || false,
    debug: options.debug || false,
    include: options.include,
    exclude: options.exclude || [],
    useBuiltIns: options.useBuiltIns || "usage",
    forceAllTransforms: options.forceAllTransforms,
    configPath: options.configPath,
    ignoreBrowserslistConfig: true,
    shippedProposals: options.shippedProposals,
    corejs: {
      version: "core-js@3",
    },
  };

  let presets = [];
  let plugins = [];

  if (options.jsx) {
    presets.push([
      require("@vue/babel-preset-jsx"),
      typeof options.jsx === "object" ? options.jsx : {},
    ]);
  }

  plugins.push(["@babel/plugin-syntax-dynamic-import"]);
  // https://babeljs.io/docs/en/next/babel-plugin-transform-runtime.html
  plugins.push([
    "@babel/plugin-transform-runtime",
    {
      useESModules: true,
      helpers: envOptions.useBuiltIns === "usage",
      regenerator: envOptions.useBuiltIns !== "usage",
      // polyfills are injected by preset-env & polyfillsPlugin, so no need to add them again
      corejs: false,
    },
  ]);

  presets.unshift(["@babel/preset-env", envOptions]);

  return {
    sourceType: "unambiguous",
    overrides: [
      {
        exclude: [/@babel[\/|\\\\]runtime/, /core-js/],
        presets,
        plugins,
      },
      {
        // there are some untranspiled code in @babel/runtime
        // https://github.com/babel/babel/issues/9903
        include: [/@babel[\/|\\\\]runtime/],
        presets: [
          [
            require("@babel/preset-env"),
            {
              useBuiltIns: envOptions.useBuiltIns,
              corejs: 3,
            },
          ],
        ],
      },
    ],
  };
};