I write my Vue project by VScode in Linux.There is a postcss.config.js in my workspace.

And it works well when I build. However, My VScode are complaining that I don't write postcss correctly as follow:

Vetur doesn't support postcss nesting. But you can use other postcss features like custom-property and @apply.
You can turn off style validation by configure option. vetur.validation.style. https://github.com/vuejs/vetur/blob/master/package.json#L133
More info and reasoning: https://github.com/Microsoft/vscode/issues/3907#issuecomment-266676745
Broadly speaking, we will keep pace with vscode team.
Most helpful comment
Vetur doesn't support postcss nesting. But you can use other postcss features like custom-property and
@apply.You can turn off style validation by configure option.
vetur.validation.style. https://github.com/vuejs/vetur/blob/master/package.json#L133More info and reasoning: https://github.com/Microsoft/vscode/issues/3907#issuecomment-266676745
Broadly speaking, we will keep pace with vscode team.