next.js/packages/next/src/build/webpack/loaders/modularize-import-loader.ts

import path from 'path'

export type ModularizeImportLoaderOptions = {
  name: string
  join?: string
  from: 'default' | 'named'
  as: 'default' | 'named'
}

/**
 * This loader is to create special re-exports from a specific file.
 * For example, the following loader:
 *
 * modularize-import-loader?name=Arrow&from=Arrow&as=default&join=./icons/Arrow!lucide-react
 *
 * will be used to create a re-export of:
 *
 * export { Arrow as default } from "join(resolve_path('lucide-react'), '/icons/Arrow')"
 *
 * This works even if there's no export field in the package.json of the package.
 */
export default function transformSource(this: any) {
  const { name, from, as, join }: ModularizeImportLoaderOptions =
    this.getOptions()
  const { resourcePath } = this
  const fullPath = join
    ? path.join(path.dirname(resourcePath), join)
    : resourcePath

  return `
export {
  ${from === 'default' ? 'default' : name} as ${
    as === 'default' ? 'default' : name
  }
} from ${JSON.stringify(fullPath)}
`
}