Error importing pure TS packages (with Bun, Turbo, or neither)

[ctjlewis]

Link to the code that reproduces this issue

https://github.com/ctjlewis/ts-package-example

To Reproduce

Repro here:

https://github.com/ctjlewis/nextjs-ts-package

It attempts to load this simple mock package:

https://github.com/ctjlewis/ts-package-example

---

Without Bun, Turbo throws:

 ⨯ ./node_modules/ts-package-example/index.ts
Module parse failed: Unexpected token (1:7)
> export type GoodNextjsSupport = false;
| export type PossibleSupport = boolean;
| 

Import trace for requested module:
./node_modules/ts-package-example/index.ts
./app/page.tsx

When Bun is used with Turbo (bun --bun next dev --turbo), we get a segfault from Bun:

Bun v1.1.41 ([`b8f28ed`](<https://github.com/oven-sh/bun/tree/b8f28ed8afd1c2b60568b2b0158d39a674178027>)) on macos aarch64 [AutoCommand]

Segmentation fault at address 0x4000000002B

- *10 unknown/js code*

<!-- from bun.report: etViGWlalFX_NMfe5SXL -->

<sub>Sentry Issue: <strong><a href="https://bun-p9.sentry.io/issues/5298323857/">BUN-85</a></strong></sub>

Current vs. Expected behavior

It's important that the module resolve and load correctly. It is effectively the simplest possible pure-TS program.

Is it maybe the module export? I will try with exports keyword after this, but either way module entrypoint is simplest config.

I doubt it is, since it seems to throw on the type keyword - is it actually expecting JS from all node_modules?

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 24.1.0: Thu Oct 10 21:05:14 PDT 2024; root:xnu-11215.41.3~2/RELEASE_ARM64_T8103
  Available memory (MB): 16384
  Available CPU cores: 8
Binaries:
  Node: 21.0.0
  npm: 10.2.0
  Yarn: 1.22.19
  pnpm: 9.7.1
Relevant Packages:
  next: 15.1.1-canary.17 // Latest available version is detected (15.1.1-canary.17).
  eslint-config-next: 15.1.2
  react: 19.0.0
  react-dom: 19.0.0
  typescript: 5.7.2
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Module Resolution, Runtime, Turbopack, TypeScript, Webpack

Which stage(s) are affected? (Select all that apply)

next dev (local), next build (local), next start (local), Vercel (Deployed), Other (Deployed)

Additional context

cc @/Jarred-Sumner for Bun crash, cc @/jaredpalmer for Turbopack, cc @/leerob for coordination.

(Config issue: Tags removed.)

[ctjlewis]

Ah, it wants us to manually specify packages to be transpiled, it does expect them all to be JS.

Why would I want my runtime import to throw because it contains TS? The simplest adjustment here is to handle this error specifically, and say, "Add { transpilePackages: ["your-package-here"] } to next.config.ts to transpile this package."

Never knew about this. I would print that message if there's ever any kind of parsing error and the import source ends in .ts or contains a type or interface keyword.

[ctjlewis]

This does not fix the issue completely, since now we get a runtime error even though the module resolves and parses:

#73662