Upgrade to webpack 4

[xPaw]

• Cannot read property 'handlebarsLoader' of undefined
  • Related to Replaced loaderContext.options with loaderContext.rootContext for upcoming Webpack 4 pcardune/handlebars-loader#153?
• warning " > babel-loader@7.1.2" has incorrect peer dependency "webpack@2 || 3".
• warning " > istanbul-instrumenter-loader@3.0.0" has incorrect peer dependency "webpack@^2.0.0 || ^3.0.0".
  • refactor(loader): v4.0.0 webpack-contrib/istanbul-instrumenter-loader#79
  • fix(package): add webpack >= v4.0.0 (peerDependencies) webpack-contrib/istanbul-instrumenter-loader#84
  • v3.0.1 is not published on npm webpack-contrib/istanbul-instrumenter-loader#85
  • Update istanbul-instrumenter-loader to the latest version 🚀 #2307
• warning " > mocha-webpack@1.0.1" has incorrect peer dependency "mocha@^2.4.5 || ^3.0.0 || ^4.0.0".
  • Allow Mocha 5 as peerDependency zinserjan/mocha-webpack#204
• warning " > mocha-webpack@1.0.1" has incorrect peer dependency "webpack@^2.0.0 || ^3.0.0".
  • Webpack v4 support zinserjan/mocha-webpack#211
• warning " > mocha-webpack@1.1.0" has incorrect peer dependency "webpack@^2.0.0 || ^3.0.0".
• warning " > webpack-dev-server@2.11.1" has incorrect peer dependency "webpack@^2.2.0 || ^3.0.0".
• warning "webpack-dev-server > webpack-dev-middleware@1.12.2" has incorrect peer dependency "webpack@^1.0.0 || ^2.0.0 || ^3.0.0".
• yarn test:browser is empty

[astorije]

A bunch of PRs in related projects are opened, I am now subscribed to all of them I believe, so I'll post here when I get notified.
Now let's see what projects come through.

Ah, the joys of major upgrades in the Webpack world...

[astorije]

yarn test:browser produces nothing, not sure why :/

[astorije]

@xPaw, you mentioned yarn test:browser works for you. Mine doesn't, super weird. Could you confirm you do not see this on your end:

[MaxLeiter]

@astorije: can confirm same issue on macOS

[xPaw]

@astorije Yeah, it's empty for me too now...

[xPaw]

I think this is ready expect for the test:browser being busted.

[astorije]

I was pretty much giving up, ended up spending way too much time on this, but it turns out a simple * fixed test:browser. Be damned, Webpack.