Webpack minimal repro for issue #16744

Reproduction steps

npm install
npm run build
npm test # or open app/index.html in a browser

You can also edit app/app-source.js to see that it fails with both import and require.

The problem

• Bundling a library into an ES Module with webpack outputs var __webpack_exports__ = {}; at the top level.
• Trying to include this ES Module in an app also built with webpack, using the eval devtool (as is default with webpack-dev-server), it outputs __webpack_require__.r(__webpack_exports__); at the very start of the eval'd code. This code seems to be expecting to reference a variable from outside the eval, but instead __webpack_exports__ is shadowed.
• At runtime, it gets an error due to __webpack_exports__ being undefined:

  Uncaught TypeError: Object.defineProperty called on non-object
      at Function.defineProperty (<anonymous>)
      at __webpack_require__.r (app-bundle.js:82:21)
      at eval (library-bundle.esm.js:1:21)
      at ../library/dist/library-bundle.esm.js (app-bundle.js:29:1)
      at __webpack_require__ (app-bundle.js:53:41)
      at eval (app-source.js:2:93)
      at ./app-source.js (app-bundle.js:19:1)
      at __webpack_require__ (app-bundle.js:53:41)
      at app-bundle.js:93:37
      at app-bundle.js:95:12