Express 5.x Compatibility Issue with Wasp-Generated Code

Backend✅SolvedTypescript

Wasp Version: 0.20.1
Express Version: 5.1.0
TypeScript Error Location: .wasp/out/sdk/wasp/server/utils.ts:28-33

Problem

After upgrading to Express 5.x (express": "~5.1.0" and @types/express": "^5.0.0"), I'm getting a TypeScript compilation error in Wasp's generated server utilities when running

wasp start

wasp start

Property 'end' does not exist on type 'void'.

Property 'end' does not exist on type 'void'.

Root Cause

The issue is in the generated redirect() helper function:

  // File: .wasp/out/sdk/wasp/server/utils.ts
  export function redirect(res: Response, redirectUri: string)  {
    return res
      .status(302)
      .setHeader("Location", redirectUri)
      .end();
  }

  // File: .wasp/out/sdk/wasp/server/utils.ts
  export function redirect(res: Response, redirectUri: string)  {
    return res
      .status(302)
      .setHeader("Location", redirectUri)
      .end();
  }

Express 4.x vs 5.x Breaking Change:
- Express 4.x: res.setHeader() returns Response (allows chaining)
- Express 5.x: res.setHeader() returns void (chaining .end() fails)

This is documented in the https://expressjs.com/en/guide/migrating-5.html.

Questions
1. Is Wasp 0.20.1 officially compatible with Express 5.x?
2. Recommended approach? Should I:
- Stay on Express 4.x for now
- Wait for an official Wasp update

Wasp•3w ago•

34 replies

YuehLin

Express 5.x Compatibility Issue with Wasp-Generated Code

Backend✅SolvedTypescript

wasp start

wasp start

Property 'end' does not exist on type 'void'.

Property 'end' does not exist on type 'void'.

Root Cause

The issue is in the generated redirect() helper function:

  // File: .wasp/out/sdk/wasp/server/utils.ts
  export function redirect(res: Response, redirectUri: string)  {
    return res
      .status(302)
      .setHeader("Location", redirectUri)
      .end();
  }

  // File: .wasp/out/sdk/wasp/server/utils.ts
  export function redirect(res: Response, redirectUri: string)  {
    return res
      .status(302)
      .setHeader("Location", redirectUri)
      .end();
  }

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