External modules not supported in subpath imports

Why this is a good first issue

Subpath imports for external modules are not supported as per Node.js specifications.

AI Summary

The issue involves subpath imports not supporting external modules as specified by Node.js documentation. The problem occurs during development and build stages, affecting module resolution. The fix likely requires changes in how Next.js handles module resolution, particularly for external packages.

Issue Description

Link to the code that reproduces this issue

https://github.com/ysulyma/nextjs-subpath-imports-external-bug

To Reproduce

Start the application in development (next dev)
You will get the error Module not found: Can't resolve '#image'

Current vs. Expected behavior

Node.js docs specify that imports field is allowed to map to external packages: https://nodejs.org/api/packages.html#subpath-imports, however this does not work.

// package.json
{
  // ...
  "imports": {
    "#image": "next/image"
  }
}

// page.tsx
import Image from "#image";

I originally encountered this issue while trying to get MathJax to server-render; they have imports in the above style as you can see from their package.json.

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 23.6.0: Fri Jul  5 17:56:39 PDT 2024; root:xnu-10063.141.1~2/RELEASE_ARM64_T8122
  Available memory (MB): 24576
  Available CPU cores: 8
Binaries:
  Node: 23.11.1
  npm: 10.9.2
  Yarn: 1.22.22
  pnpm: 10.25.0
Relevant Packages:
  next: 16.2.0 // Latest available version is detected (16.2.0).
  eslint-config-next: N/A
  react: 19.2.4
  react-dom: 19.2.4
  typescript: 5.9.3
Next.js Config:
  output: N/A

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

Module Resolution, Turbopack

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

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

Additional context

No response

GitHub Labels

TurbopackModule Resolution