Webpack 4. SplitChunks duplication

Question

I'm using Webpack 4 and wanted to split two entry points and avoid duplication. So, I have react and react-dom in both chunks.

entry: {
    index: ['babel-polyfill', './app/app.jsx'],
    vendor: [
        'react',
        'react-dom'
    ]
}


splitChunks: {
            cacheGroups: {
                index: {
                    minChunks: 2,
                    priority: -20,
                    reuseExistingChunk: true
                },
                vendor: {
                    test: /[\\/]node_modules[\\/]/,
                    priority: -10
                }
            }
        }