rsnext/test/integration/getserversideprops-preview/pages/index.js

export function getServerSideProps({ res, preview, previewData }) {
  // test override in preview mode
  res.setHeader('Cache-Control', 'public, max-age=3600')
  return {
    props: {
      hasProps: true,
      preview: !!preview,
      previewData: previewData || null,
    },
  }
}

export default function({ hasProps, preview, previewData }) {
  if (!hasProps) {
    return <pre id="props-pre">Has No Props</pre>
  }

  return (
    <pre id="props-pre">
      {JSON.stringify(preview) + ' and ' + JSON.stringify(previewData)}
    </pre>
  )
}