[BUG]: Multer Upload Errors Not Handled — Server Returns Unformatted Crash Response

[Anushka-045]

📌 Problem

The multer middleware in admin.routes.js throws errors when an invalid file type is uploaded, but these errors are never caught by an error handler. This causes the server to return an unformatted crash response instead of a clean JSON error message, which is bad for UX and security.

💡 Proposed Solution

Add a dedicated multer error handler middleware in admin.routes.js that:

• Catches MulterError (e.g. file too large)
• Catches custom fileFilter errors (wrong file type)
• Returns a clean JSON response with a proper status code and message

🎯 Benefits

• Prevents server crashes from invalid file types
• Improves security by blocking unexpected uploads
• Gives users a clear error message instead of a crash

⚙️ Implementation

Add this after the upload route:

router.use((err, req, res, next) => {
if (err instanceof multer.MulterError || err.message) {
return res.status(400).json({
status: 'error',
message: err.message
});
}
next(err);
});

I'd like to work on this!

[Anushka-045]

Hi @itsmnx, here are the clarifications:

1. Existing validation — Yes, the current middleware in admin.routes.js already validates file type (.xlsx and .xls only) and file size (5MB limit) using multer's fileFilter and limits options. However, the errors thrown are never caught, causing unformatted crash responses.

2. File to modify — Only backend/routes/admin.routes.js will be modified. No other files will be touched.

3. Error handling approach — A dedicated error handler middleware will be added at the bottom of admin.routes.js:

   • MulterError with code LIMIT_FILE_SIZE → file too large
   • Any other MulterError → generic upload error
   • Custom fileFilter error → wrong file type

4. JSON response format:

   • Wrong file type: { status: 'error', message: 'Only Excel files (.xlsx, .xls) are allowed' }
   • File too large: { status: 'error', message: 'File is too large. Maximum size allowed is 5MB' }
   • Both return HTTP 400

5. Existing functionality — Valid .xlsx and .xls uploads under 5MB will continue to work exactly as before. Only error responses are improved.

[Anushka-045]

Hi @itsmnx, just wanted to check — will this contribution be counted for NSOC points on the leaderboard? If yes, could you please add the NSOC label? Thank you! 🙏