next.js/packages/next/build/webpack/plugins/serverless-plugin.ts

import {Compiler} from 'webpack'
import GraphHelpers from 'webpack/lib/GraphHelpers'
/**
 * Makes sure there are no dynamic chunks when the target is serverless
 * The dynamic chunks are integrated back into their parent chunk
 * This is to make sure there is a single render bundle instead of that bundle importing dynamic chunks
 */
export class ServerlessPlugin {
  apply (compiler: Compiler) {
    compiler.hooks.compilation.tap('ServerlessPlugin', compilation => {
      compilation.hooks.optimizeChunksBasic.tap(
        'ServerlessPlugin',
        chunks => {
          chunks.forEach((chunk) => {
            // If chunk is not an entry point skip them
            if (chunk.hasEntryModule()) {
              const dynamicChunks = chunk.getAllAsyncChunks()
              if (dynamicChunks.size !== 0) {
                for (const dynamicChunk of dynamicChunks) {
                  for (const module of dynamicChunk.modulesIterable) {
                    GraphHelpers.connectChunkAndModule(chunk, module)
                  }
                }
              }
            }
          })
        }
      )
    })
  }
}