2.0.0 SourceMap not working in build mode

[RunningCoderLee]

Is this a bug report?

yes

Did you try recovering your dependencies?

yes

Environment

System:
OS: macOS 10.14
CPU: x64 Intel(R) Core(TM) i7-4870HQ CPU @ 2.50GHz
Binaries:
Node: 10.9.0 - ~/.nvm/versions/node/v10.9.0/bin/node
Yarn: 1.9.4 - /usr/local/bin/yarn
npm: 6.4.1 - ~/.nvm/versions/node/v10.9.0/bin/npm
Browsers:
Chrome: 69.0.3497.100
Firefox: 62.0
Safari: 12.0
npmPackages:
react: ^16.5.2 => 16.5.2
react-dom: ^16.5.2 => 16.5.2
react-scripts: 2.0.0 => 2.0.0
npmGlobalPackages:
create-react-app: 2.0.0

Steps to Reproduce

(Write your steps here:)

1. create-react-app my-react --scripts-version=@next
2. yarn build

Expected Behavior

generate .css.map file

Actual Behavior

not generate .css.map file

[RunningCoderLee]

This problem Looks like caused by optimize-css-assets-webpack-plugin, when I modify the configuration as below, it works for me

new OptimizeCSSAssetsPlugin({
  cssProcessorOptions: { 
    parser: safePostCssParser,
    map: {
      inline: false,
      annotation: true
    }
  },
})

refs:
webpack-contrib/mini-css-extract-plugin#141
NMFR/optimize-css-assets-webpack-plugin#53