CSS not added to /dist folder using Webpack 4 and MiniCssExtractPlugin

Question

Issue

Would any Webpack config experts out there be able to tell me why I can't extract my css into the dist folder when running npm run build? Repo is here: https://github.com/damodog/webpack4-boilerplate

Further info

To summarise, I've been working through the Webpack Guide docs and everything was going well. js and css was getting injected into my index.html file via <link> and <script> tags respectively. I've installed various loaders, plugins etc and split my configs out into common (shared), dev and prod files (as per the docs) and life was good.

I happened to make some tweaks which included looking at code splitting dynamic imports, adding aliases for paths, moving js into js folder etc and noticed when I ran a build npm run build all of a sudden my css wasn't getting added to the dist folder. I reverted my trial changes for the dynamic import stuff and tried reverting the other changes but am still getting the same issue. Annoyingly I hadn't added git at this point so didn't have a clear picture of the 'tweaks' I'd made to locate what I'd changed.

What happens

When I run my watch task npm start the styles.scss file (imported into the main index.js file) get's compiled into css and the resulting app.css file gets injected into the index.html page when viewed in my local host. All gravy. <link href="css/app.css" rel="stylesheet">

When I run npm run build the css file should get copied over dist folder, a hash id should get added and the css should be minified. This was working (like I said above) and I could see the css file in the build steps (see first Asset below. Btw disregard the difference in js bundled files here compared to the next screenshot. This was when I was playing with code splitting).

Now when I run this the css isn't bundled up (see below).

I think it could be something to do with mini-css-extract-plugin but I've configured this as per the docs using the advanced configuration example (I've split their example out which is in one config file as I have separate config files for dev and prod).

I literally cannot see why this is happening. Help me SO readers. You're my only help...

Answer 1

I cloned your repo and experimented with it. In your package.json, you've set: sideEffects: false. This causes the imported stylesheets to be lost in the process of tree shaking. This is described in the docs:

A "side effect" is defined as code that performs a special behavior when imported, other than exposing one or more exports. An example of this are polyfills, which affect the global scope and usually do not provide an export.

and

Note that any imported file is subject to tree shaking. This means if you use something like css-loader in your project and import a CSS file, it needs to be added to the side effect list so it will not be unintentionally dropped in production mode

So change your side effects in package.json to "sideEffects: ["./src/scss/styles.scss"] and it will be output to the destination folder when in production mode.