Webpack: Can't resolve 'fs'

[tessereth]

I tried pulling in this npm package and compiling it with webpack but I get the following errors:

ERROR in ./node_modules/micropython/index.js
Module not found: Error: Can't resolve 'fs' in './micropython_example/node_modules/micropython'
 @ ./node_modules/micropython/index.js 21:9-22
 @ ./assets/js/app.js
 @ ./assets/js/index.js

ERROR in ./node_modules/micropython/lib/micropython.js
Module not found: Error: Can't resolve 'fs' in './micropython_example/node_modules/micropython/lib'
 @ ./node_modules/micropython/lib/micropython.js 39:15-28 80:13-26 179:28-41 3005:23-36
 @ ./node_modules/micropython/index.js
 @ ./assets/js/app.js
 @ ./assets/js/index.js

This appears to be because webpack is not detecting that it can never go down the "node-only" path and still trying to require fs. If I add typeof __webpack_require__ !== 'function' on every branch that requires fs, everything works. But I don't know enough about webpack to be confident such changes are a good idea and/or they wouldn't break it for someone else.

You can see my webpack version and config and a working example at https://github.com/tessereth/micropython_wasm_example.

[tessereth]

Reading through various issues (including webpack/webpack#7352), looks like you can get around issues in the emscripten generated javascript (lib/micropython.js) by adding an ignore plugin to the webpack config:

  plugins: [
    ...
    new webpack.IgnorePlugin(/^fs$/),
  ],

This does not fix the issue in index.js. I'm pretty sure this code:

micropython-wasm/index.js

Lines 20 to 22 in 0672c9e

	if (typeof webpackJsonp !== 'object') {
	pyjs = require('fs').readFileSync(__dirname + '/js.py').toString();
	}

does not work as intended. When running in the brower, webpackJsonp is undefined even when it was originally built with webpack. Perhaps using typeof window === 'undefined' would be better?