packages/next/server/on-demand-entry-handler.js
function addEntry (compilation, context, name, entry) {
  return new Promise((resolve, reject) => {
    const dep = DynamicEntryPlugin.createDependency(entry, name)
    compilation.addEntry(context, dep, name, (err) => {
      if (err) return reject(err)
      resolve()
    })
  })
}
function addEntry (compilation, context, name, entry) {
  return new Promise((resolve, reject) => {
    const dep = DynamicEntryPlugin.createDependency(entry, name)
    compilation.addEntry(context, dep, name, (err) => {
      if (err) return reject(err)
      resolve()
    })
  })
}
Based on https://github.com/webpack/webpack/blob/master/lib/DynamicEntryPlugin.js#L29-L37