Next js 15 error list

 

Next.js, being a robust React framework for server-side rendering and static site generation, comes with its own set of common errors and issues. Here’s a comprehensive list of errors you might encounter while developing with Next.js, along with brief explanations:

1. Syntax and Build Errors

• SyntaxError: Unexpected token: This could be due to syntax issues like missing parentheses, brackets, or other characters in your code.
• Module not found: Can't resolve 'module-name': Occurs when a module or package cannot be found. Ensure the package is installed and correctly imported.
• Unexpected reserved word 'export' or 'import': Indicates that the project is not transpiling ES6 syntax properly. Check next.config.js or your Babel configuration.

2. Routing and Navigation Issues

• 404 Error (Page not found): When a route does not match any defined page, Next.js returns a 404 error.
• Error: A required parameter (e.g., 'id') was not provided as part of the URL: This happens when using dynamic routing without the necessary URL parameters.
• next/link href should not include repeated path segments: Incorrect href values in the Link component.

3. Server-side Rendering (SSR) Errors

• ReferenceError: window is not defined: Occurs when server-side rendering tries to access window, which is only available in the browser.
• ReferenceError: document is not defined: Similar to the window error, this happens when trying to access document during SSR.
• Unhandled Promise Rejection: This can happen when an async function does not handle errors properly in getServerSideProps or getStaticProps.

4. Data Fetching Errors

• Error during getServerSideProps or getStaticProps: These errors usually stem from failed data fetching logic, incorrect use of APIs, or returning incorrect data types.
• TypeError: Cannot read property 'X' of undefined: Caused by accessing properties on undefined or null values in data fetching functions.
• Timeouts in data fetching: Long data fetching times can result in timeouts or blocked rendering.

5. API Route Issues

• 404 Error for API route: Occurs when the route path is incorrect or does not match the defined API routes in the pages/api folder.
• CORS (Cross-Origin Resource Sharing) error: When making requests from the client to an API that doesn't have proper CORS headers set.
• Error: API resolved without sending a response: Happens when an API route doesn’t return a response to the client.

6. Static Site Generation (SSG) Errors

• Error: getStaticPaths is required for dynamic SSG pages: Dynamic routes need getStaticPaths to be defined for static generation.
• getStaticProps returned undefined: The function should return an object containing props or a notFound key.
• Invalid getStaticPaths value: The getStaticPaths function must return an array of path objects and a fallback value.

7. Image Optimization Errors (Next.js Image Component)

• Error: Invalid src prop (must be a valid URL or import): Occurs when the src prop for the Image component is incorrectly provided.
• Error: hostname is not configured under images in next.config.js: This happens when using external URLs for the Image component without allowing them in next.config.js.
• The provided src prop is not a valid image URL: The src value must be a valid, absolute URL.

8. Deployment Errors

• Application errors on Vercel or other platforms: These can include build time errors, incorrect environment variables, or API rate limits.
• Failed to deploy: The build failed because of a syntax error: General error during the build process due to code issues.
• Environment variable not defined: Make sure all required environment variables are set during the build and runtime.

9. Webpack and Build Configuration Errors

• Webpack not configured properly: Issues with custom Webpack configurations in next.config.js.
• Babel issues: Problems with custom Babel configurations that are not compatible with Next.js.
• Error: Cannot find module 'webpack': Ensure that all dependencies are correctly installed.

10. React and Hooks Errors

• Invalid hook call: Hooks are only valid in functional components or custom hooks, not outside of these contexts.
• React Hydration Error: Occurs when the server-rendered content does not match the client-rendered content.
• Component mismatches between server and client: Can happen if conditional rendering logic differs between server and client.

11. Styling Issues

• Global CSS cannot be imported from files other than your Custom <App>: Global CSS imports are restricted to pages/_app.js.
• Flickering styles during navigation: Happens when styles are not properly scoped or imported.
• CSS Module not found: Incorrect path or filename when using CSS modules.

12. TypeScript Errors

• Type errors related to props: Incorrect prop types when using TypeScript with Next.js.
• TypeScript configuration issues: Problems due to incorrect settings in tsconfig.json.
• Error: JSX element type 'X' does not have any construct or call signatures: Issues with TypeScript typing for JSX elements.

13. Environment and Configuration

• process.env undefined: Ensure that environment variables are defined in .env.local, .env, or during deployment.
• Invalid next.config.js configuration: Errors related to incorrect settings or modules in next.config.js.
• NEXT_PUBLIC_ prefix missing: Client-side environment variables must use the NEXT_PUBLIC_ prefix to be accessible on the client.

14. Performance Warnings

• Large JavaScript bundles: Use next dev or next build to see performance metrics and reduce the bundle size.
• Too many re-renders: Caused by improper state management leading to infinite re-rendering loops.

15. Miscellaneous

• Error: Only absolute URLs are supported: In fetch requests, using relative URLs without a base URL.
• Next.js version compatibility issues: Newer features may not be available in older versions of Next.js.
• Custom server errors: Issues when using custom server logic with Next.js.

Understanding and debugging these errors typically involve carefully reading the error messages, checking the Next.js documentation, using browser developer tools, and reviewing your code logic.