Turbopack: support named chunks with turbopackChunkName / webpackChunkName

[karlhorky]

Edit: Reported as a webpack-to-Turbopack migration regression in #100051

Current vs. Expected behavior

Currently, Turbopack in Next.js 16.4.0 ignores webpackChunkName comments. For example, React Player names its YouTube import:

import(
  /* webpackChunkName: 'reactPlayerYouTube' */
  'youtube-video-element/react'
)

webpack emits reactPlayerYouTube.<hash>.js, while Turbopack emits a generated filename such as 1z1qq2nqxoa77.js.

Expected: support turbopackChunkName and/or the existing webpackChunkName comment, retaining a content hash in the filename.

Use case

Identify third-party code in browser console messages and network requests. Our Playwright tests ignore a known YouTube progress log by its chunk URL. After switching to Turbopack, the filename no longer identifies the YouTube code, requiring a broader filter.

Additional context

An implementation was proposed in #95409, but closed without merging. This request tracks the use case separately from that implementation.

[lukesandberg]

We discussed this and don't think this is a good fit for turbopack.

Adding names to output files like this is ambiguous

import(/* webpackChunkName: "video-player" */  "./VideoPlayer.tsx")
// another file:
import(/* webpackChunkName: "bar" */  "./VideoPlayer.tsx")
// third file:
import("./VideoPlayer.tsx")

should those all be the same output file? different ones? the closed PR on this would pick the shortest name as canonical (which would be "" or bar but both are surprising to the first caller )

[karlhorky]

Understood, that does make it complicated!

Maybe in the case of conflicts, it should be a Turbopack build error?

[lukesandberg]

have you considered communicating with your dependency about fixing their log lines? this would be a very complex chunking change to support a fairly narrow usecase