## Context
When upgrading to Next.js 6.1.1-canary.4 and using the `emit-file-loader` included in Next.js, the following error is thrown:
```bash
error in ./src/graveyard/pages/_app.scss
Module build failed (from ../node_modules/next/dist/build/webpack/loaders/emit-file-loader.js):
TypeError: Cannot read property 'context' of undefined
at Object.module.exports (~/project-root/node_modules/next/dist/build/webpack/load
ers/emit-file-loader.js:27:68)
@ ./src/pages/_app.js 35:0-53 156:17-26 157:13-22
@ multi ./pages/_app.js
```
`next.config.js` (shortened):
```js
module.exports = {
webpack: (config, { dev }) => {
config.module.rules.push({
test: /\.scss$/,
use: [
{
loader: 'emit-file-loader',
options: {
name: 'dist/[path][name].[ext].js'
}
},
{
loader: 'babel-loader',
options: {
babelrc: false,
extends: path.resolve(__dirname, './src/.babelrc')
}
},
'styled-jsx-css-loader',
{ loader: 'postcss-loader', options: { sourceMap: dev } },
{
loader: 'sass-loader',
options: {
sourceMap: dev
}
}
]
});
return config;
}
};
```
## Suggested Fix
A quick Google search brought me to a [related issue in `webpack-loader`](https://github.com/webpack-contrib/worker-loader/issues/125). As pointed out in the [Webpack docs](https://webpack.js.org/api/loaders/#this-rootcontext):
> Starting with webpack 4, the formerly `this.options.context` is provided as `this.rootContext`.
This PR makes this change while maintaining backward compatibility.
## System information
Next.js: 6.1.1-canary.4
Node: v9.3.0
Depends on https://github.com/zeit/next-plugins/pull/228
Failing tests are expected as `@zeit/next-css` has to be updated/released first.
This implements rendering of `.css` chunks. Effectively removing the custom document requirement when adding next-css/sass/less/stylus.
* Compile pages to .next/static/<buildid>/pages/<page>
* Fix test
* Export class instead of using exports
* Use constant for static directory
* Add comment about what the middleware does
Fixes#4686
Adds tests for @zeit/next-typescript so that we don't regress on this again.
I've fixed an issue in the `next` CLI too which caused lingering processes when the process gets force killed, which is what we do in the test suite, so it kept running if there was no manual quit.
I have spend whole day on profiling next.js compiling performance and one of the easy hacks to reduce built time is avoid doing full `stats.toJson()` that is heavy by default.
This makes sure plugins like @zeit/next-typescript or @zeit/next-mdx don't have to provide the `hot-self-accept-loader`.
This fixes for example @zeit/next-mdx, which doesn't implement `pageExtensions` but we do use mdx as top level pages for https://github.com/zeit/docs
The prepares for next-server.
I also took this as an opportunity to get all build directory paths from a single location, as they were previously scattered across webpack/babel plugins and loaders.
