Error: Missing or invalid getStaticProps return in Next.js: Causes and How to Fix

Ensure Proper Return in getStaticProps

• Make sure the `getStaticProps` function returns an object that includes a `props` key. This key should hold the props that you want to pass down to your page component.

 

• If there is a need to pass additional data like revalidating time, make sure it is correctly incorporated. For example, `return { props: { data }, revalidate: 10 }`. Always ensure every property in the return object is correct.

export async function getStaticProps() {
  const data = await fetchData();
  return { props: { data } };
}

Handle the Undefined Returns

• If there is a possibility that your data fetching might return nothing (undefined), ensure this case is handled properly by checking and setting fallback values or handling errors gracefully.

export async function getStaticProps() {
  const data = await fetchData();

  if (!data) {
    return { notFound: true };
  }

  return { props: { data } };
}

Validate Async/Await Usage

• Ensure that all asynchronous operations inside `getStaticProps` are correctly awaited. Operations like fetching data from an API or database should be prefixed with the `await` keyword if they return a Promise.

export async function getStaticProps() {
  const response = await fetch('https://api.example.com/data');
  const data = await response.json();

  return { props: { data } };
}

Verify Correct Export

• Ensure that `getStaticProps` is an exported function. It should be a named export from your page component file. Without proper export, Next.js cannot recognize the function, causing errors with the props.

export async function getStaticProps() {
  // function body
}

Debug and Log Output

• Use console logs or debugging tools to print variables and ensure that your data fetching logic is correct. This can help you understand what exactly is being returned by your asynchronous operations.

export async function getStaticProps() {
  const response = await fetch('https://api.example.com/data');
  const data = await response.json();

  console.log(data); // Debug log to check data output

  return { props: { data } };
}

Address TypeScript Issues

• For TypeScript users, correctly type the return value of `getStaticProps` using `GetStaticProps` provided by Next.js to ensure type checking at compile time.

import { GetStaticProps } from 'next';

export const getStaticProps: GetStaticProps = async (context) => {
  const data = await fetchData();
  return { props: { data } };
}