[Webpack] Invalid CSS after "@include mixins"

Bug report

Hello, I try to pack mdc with Webpack and Typscript.

In Version 4.0.0 I get this error:

ERROR in [at-loader] ./node_modules/@material/auto-init/index.d.ts:38:16 
    TS2528: A module cannot have multiple default exports.

This is fixed by Version: “^5.0.0-canary.faa9af310.0” But now I have the error:

ERROR in ./src/frontend/sass/main.scss
Module build failed (from ./node_modules/sass-loader/dist/cjs.js):
SassError: Invalid CSS after "@include mixins": expected 1 selector or at-rule, was ".core-styles;"
        on line 24 of node_modules/@material/button/mdc-button.scss

Steps to reproduce

1 Create a Example Project like this. https://github.com/material-components/material-components-web/blob/master/docs/getting-started.md 2. update mdc: npm i [e-mail]9af310.0 3. run npm: npm start

Your Environment:

Software	Version(s)
MDC Web	5.0.0-canary.faa9af310.0
Browser	chrome
Operating System	Debian 10

Possible solution

The only way to fix both problems, go to version 2.3.1.

[abraham]

I was getting

ERROR in ./src/frontend/sass/main.scss Module build failed (from ./node_modules/sass-loader/dist/cjs.js): SassError: Invalid CSS after “@include mixins”: expected 1 selector or at-rule, was “.core-styles;” on line 24 of node_modules/@material/button/mdc-button.scss

and fixed it by removing node-sass and installing sass@1.25.0.

[abhiomkar]

I created full working example with some of the popular bundlers: Webpack, Rollup & Snowpack.