nextjs - 💡(How to fix) Fix [Turbopack] Duplicate class definitions across route chunks, breaking `instanceof` [2 comments, 3 participants]

grep -c "class e extends d.ServiceException" .next/server/app/api/*/route.js

TL;DR

• Consider configuring next.config.js to optimize how Turbopack handles external packages, specifically by adjusting serverExternalPackages or exploring other bundling options to ensure consistent class definitions across routes.

Guidance

• Review the next.config.js file to understand how external packages are currently being handled, particularly focusing on the serverExternalPackages configuration.
• Experiment with adding more packages to serverExternalPackages that are commonly used across routes to see if this resolves the instanceof issue.
• Investigate if there are other Turbopack or Next.js configurations that could help in creating a shared chunk for commonly used classes, thus preserving instanceof behavior.
• Consider the implications of using serverExternalPackages as a workaround and evaluate if this approach scales well with the project's growth.

Example

No specific code example is provided due to the complexity and variability of project configurations. However, the general approach would involve modifying the next.config.js file to include necessary packages in serverExternalPackages, like so:

module.exports = {
  //... other configurations
  serverExternalPackages: [
    // Add packages here that should be excluded from Turbopack's automatic inlining
    'aws-sdk',
    // Other packages...
  ],
}

Notes

• The provided workaround of adding AWS SDK clients to serverExternalPackages may not be ideal for all projects due to potential performance implications or limitations in handling a large number of external packages.
• Further investigation into Turbopack's configuration options or exploring alternative bundling strategies might yield a more scalable solution.

Recommendation

• Apply workaround: Adjusting serverExternalPackages in next.config.js seems to be the most straightforward approach to mitigate the issue, given the current information. This method allows for explicit control over how external packages are handled during the build process.