backend: Add middleware to handle JSON syntax errors in request bodies

backend/src/middlewares/content-type.middleware.ts

@@ -16,3 +16,26 @@ export const mediaTypeValidatorMiddleware = (req: Request, res: Response, next:
 
 	next();
 };
+
+/**
+ * Express middleware that handles JSON syntax errors in request bodies.
+ * If a SyntaxError with status 400 is detected and contains a 'body' property,
+ * it responds with a 400 Bad Request status and a JSON error message.
+ * Otherwise, it passes the error to the next middleware in the chain.
+ *
+ * @param err - The error object that was caught
+ * @param req - The Express request object
+ * @param res - The Express response object
+ * @param next - Express next function to continue to the next middleware
+ */
+export const jsonSyntaxErrorHandler = (err: any, req: Request, res: Response, next: NextFunction): void => {
+	// This middleware handles JSON syntax errors
+	if (err instanceof SyntaxError && (err as any).status === 400 && 'body' in err) {
+		res.status(400).json({
+			error: 'Bad Request',
+			message: 'Malformed Body'
+		});
+	} else {
+		next(err);
+	}
+};

backend/src/server.ts

@@ -27,6 +27,7 @@ import {
 } from './routes/index.js';
 import { internalParticipantsRouter } from './routes/participants.routes.js';
 import cookieParser from 'cookie-parser';
+import { jsonSyntaxErrorHandler } from './middlewares/content-type.middleware.js';
 
 const createApp = () => {
 	const app: Express = express();
@@ -44,6 +45,7 @@ const createApp = () => {
 	// Serve static files
 	app.use(express.static(publicFilesPath));
 	app.use(express.json());
+	app.use(jsonSyntaxErrorHandler);
 	app.use(cookieParser());
 
 	// Public API routes