next.js/packages/next-server/server/get-dynamic-import-bundles.ts

export type ManifestItem = {
  id: number|string,
  name: string,
  file: string,
  publicPath: string,
}

export type Manifest = {[moduleId: string]: ManifestItem[]}

type DynamicImportBundles = Set<ManifestItem>

// Based on https://github.com/jamiebuilds/react-loadable/pull/132
export function getDynamicImportBundles(manifest: Manifest, moduleIds: string[]): DynamicImportBundles {
  return moduleIds.reduce((bundles: DynamicImportBundles, moduleId: string): DynamicImportBundles => {
    if (typeof manifest[moduleId] === 'undefined') {
      return bundles
    }

    manifest[moduleId].map((item) => bundles.add(item))
    return bundles
  }, new Set())
}