Vuepress: Error extracting metadata

[ederchrono]

I just installed VuePress on a project and I'm getting this error after running the dev command:

Extracting site metadata...TypeError: Cannot match against 'undefined' or 'null'.
    at Object.<anonymous> (/.../node_modules/mini-css-extract-plugin/dist/index.js:26:9)

The project is not that recent, it was created with an older Vue CLI than the latest and I'm not sure if there's a config or dependency that's causing a conflict.

Installed with npm as a dev dependecy, not globally

[ederchrono]

I just made a branch with the error https://github.com/ederchrono/vue-css-grid/tree/feat/add-vuepress
Just npm i and then npm run docs:dev
Also when installing dependencies it throws these warnings:

npm WARN [email protected] requires a peer of webpack@^4.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN [email protected] requires a peer of webpack@^4.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN [email protected] requires a peer of webpack@^4.4.0 but none is installed. You must install peer dependencies yourself.
npm WARN [email protected] requires a peer of webpack@>=4.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN [email protected] requires a peer of webpack@^4.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN [email protected] requires a peer of webpack@^4.0.0 but none is installed. You must install peer dependencies yourself.

Installing webpack 4 after that makes vuepress work but breaks my project

[yyx990803]

Did you see the warning in docs? You need to use Yarn if your project has webpack 3 in dependencies.

[ederchrono]

Thanks for pointing that out! Looks like I was looking to an old version of the getting started guide or something because it used npm for the instructions instead of yarn.

Keep up the good work!