Fix: The Endpoint Did Not Return a Response in Astro

What Causes This Error?

This error occurs when an API endpoint doesn’t return a valid Response object. All HTTP method handlers (GET, POST, etc.) in endpoint files must return a Response.

The Problem

// src/pages/api/data.ts
export async function GET() {
  // ❌ No return statement
  const data = await fetchData();
}

export async function GET() {
  // ❌ Returning plain object
  return { data: 'hello' };
}

The Fix

Return a Response Object

// src/pages/api/data.ts
export async function GET() {
  const data = await fetchData();
  // ✅ Return proper Response
  return new Response(JSON.stringify(data), {
    headers: { 'Content-Type': 'application/json' },
  });
}

Or Use Response.json()

export async function GET() {
  const data = await fetchData();
  // ✅ Shorthand for JSON response
  return Response.json(data);
}

Common Scenarios

GET Endpoint

// src/pages/api/users.ts
export const prerender = false;

export async function GET() {
  const users = await db.users.findMany();
  return Response.json(users);
}

POST Endpoint

// src/pages/api/users.ts
export async function POST({ request }) {
  const body = await request.json();
  const user = await db.users.create({ data: body });

  return Response.json(user, { status: 201 });
}

Error Responses

export async function GET({ params }) {
  const user = await db.users.findUnique({ id: params.id });

  if (!user) {
    // ✅ Return error response
    return new Response('User not found', { status: 404 });
  }

  return Response.json(user);
}

Conditional Returns

// ❌ Not all paths return
export async function GET({ params }) {
  if (params.id === 'special') {
    return Response.json({ special: true });
  }
  // Missing return for other cases!
}

// ✅ All paths return
export async function GET({ params }) {
  if (params.id === 'special') {
    return Response.json({ special: true });
  }
  return Response.json({ regular: true });
}

Early Returns

export async function POST({ request }) {
  // Validate
  if (!request.headers.get('authorization')) {
    // ✅ Early return for errors
    return new Response('Unauthorized', { status: 401 });
  }

  const data = await processRequest(request);
  return Response.json(data);
}

Different HTTP Methods

// src/pages/api/resource.ts

export async function GET() {
  return Response.json({ method: 'GET' });
}

export async function POST({ request }) {
  const body = await request.json();
  return Response.json({ method: 'POST', body });
}

export async function PUT({ request }) {
  return Response.json({ method: 'PUT' });
}

export async function DELETE() {
  return new Response(null, { status: 204 });
}

Async Operations

export async function GET() {
  try {
    const data = await fetchExternalAPI();
    return Response.json(data);
  } catch (error) {
    // ✅ Return error response
    return Response.json(
      { error: 'Failed to fetch' },
      { status: 500 }
    );
  }
}

Response Types

// JSON
return Response.json({ data: 'value' });

// Text
return new Response('Plain text');

// HTML
return new Response('<h1>Hello</h1>', {
  headers: { 'Content-Type': 'text/html' },
});

// Redirect
return Response.redirect('https://example.com');

// No content
return new Response(null, { status: 204 });

// Stream
return new Response(readableStream);

TypeScript Return Type

import type { APIRoute } from 'astro';

// TypeScript will enforce Response return
export const GET: APIRoute = async ({ params }) => {
  return Response.json({ id: params.id });
};

Quick Checklist

• All code paths must return a Response
• Use Response.json() for JSON responses
• Use new Response() for other types
• Include error responses in catch blocks
• Check conditional branches all return