bundling CesiumJS using RollupJS - cesiumjs

Question

I am trying to bundle CesiumJS with Rollup. I thought I could just do an import like this:
import Cesium from 'cesium/Build/Cesium/Cesium.js'
with the following rollup.config.js file. I am getting a bundle.js but when I run it I get lots errors:
Uncaught TypeError: Cannot read property 'document' of undefined
at bundle.js:formatted:102314
function() {
!function(e) {
var t = this || eval("this")
, r = t.document // it is complaining on this line
, i = t.navigator
, n = t.jQuery
, o = t.JSON;
rollup.config.js
import resolve from 'rollup-plugin-node-resolve'
import commonjs from 'rollup-plugin-commonjs'
import uglify from 'rollup-plugin-uglify'
import { minify } from 'uglify-es'
export default {
input: 'scripts/Main.js',
output: {
file: 'dist/bundle.js',
format: 'es',
},
"options": {
sourceMap: 'inline',
output: {
format: 'es'
}
},
plugins: [
resolve({
jsnext: true,
main: true,
browser: true,
}),
commonjs(),
uglify({}, minify)
]
}

Answer 1

ES modules are always in strict mode — by extension, when something is imported into Rollup and converted to an ES module, it also runs in strict mode.
In strict mode, the value of this inside a function is undefined, unless it's a) called as a method, or b) explicitly set with call or apply.
This is expected behaviour with Rollup, and it isn't technically a bug with Cesium, but I would suggest raising an issue with them and seeing if they can use a more modern way of accessing the global variable. There's really no reason to be relying on non-strict behaviour in 2017!
As a last resort you could string-replace this || eval("this") (or this||(0,eval)("this"), as it is in the minified version) with window.
If there are lots of other errors after making that change, it may be impossible to include Cesium in your bundle, and you would need to keep it as an external module.