fix: css.extract options handling

close #1061

docs/config.md

@@ -40,6 +40,7 @@ module.exports = {
   // CSS related options
   css: {
     // extract CSS in components into a single CSS file (only in production)
+    // can also be an object of options to pass to extract-text-webpack-plugin
     extract: true,
 
     // enable CSS source maps?

packages/@vue/cli-service/lib/config/css.js

@@ -103,18 +103,15 @@ module.exports = (api, options) => {
 
     // inject CSS extraction plugin
     if (extract) {
-      const userOptions = options.extractCSS && typeof options.extractCSS === 'object'
-        ? options.extractCSS
+      const extractOptions = userOptions.extract && typeof userOptions.extract === 'object'
+        ? userOptions.extract
         : {}
       webpackConfig
         .plugin('extract-css')
           .use(ExtractTextPlugin, [Object.assign({
             filename: `css/[name].[contenthash:8].css`,
             allChunks: true
-          }, userOptions)])
+          }, extractOptions)])
     }
-
-    // TODO document receipe for using css.loaderOptions to add `data` option
-    // to sass-loader
   })
 }

packages/@vue/cli-service/lib/options.js

@@ -16,7 +16,7 @@ const schema = createSchema(joi => joi.object({
   // css
   css: joi.object({
     modules: joi.boolean(),
-    extract: joi.boolean(),
+    extract: joi.alternatives().try(joi.boolean(), joi.object()),
     localIdentName: joi.string(),
     sourceMap: joi.boolean(),
     loaderOptions: joi.object({