[WIP] Fix for server actions headers problems

examples/next-auth/src/middleware.ts

@@ -34,7 +34,10 @@ const middlewares = {
     },
     async ({ request }: MiddlewareFunctionProps) => {
       console.log('Middleware for /page2', request.nextUrl.pathname);
-      console.log('Authenticated header value:', request.headers.get('x-authenticated'));
+      console.log(
+        'Authenticated header value:',
+        request.headers.get('x-authenticated'),
+      );
       return NextResponse.redirect('http://localhost:3002/page1');
     },
   ],

packages/nemo/src/index.ts

@@ -14,6 +14,10 @@ export type NextMiddleware = (
 
 export type MiddlewareContext = Map<string, unknown>;
 
+interface NEMOConfig {
+  excludedHeaders: string[];
+}
+
 /**
  * Properties passed to middleware functions.
  */
@@ -35,6 +39,22 @@ export type MiddlewareConfig = Record<
   MiddlewareFunction | MiddlewareFunction[]
 >;
 
+const defaultExcludedHeaders = ['content-type'];
+
+/**
+ * Filters out excluded headers from the response.
+ * @param response - The response to filter headers from.
+ * @param excludedHeaders - The list of headers to exclude.
+ */
+function filterHeaders(
+  response: NextResponse,
+  excludedHeaders: string[],
+): void {
+  excludedHeaders.forEach((header) => {
+    response.headers.delete(header);
+  });
+}
+
 /**
  * Checks if the given middleware function is a legacy middleware.
  * @param middleware - The middleware function to check.
@@ -80,12 +100,14 @@ async function executeMiddleware(
  * Creates a middleware function that executes the given middleware functions.
  * @param pathMiddlewareMap - The map of paths to middleware functions.
  * @param globalMiddleware - The global middleware functions to execute
+ * @param config - The configuration for the NEMO.
  */
 export function createMiddleware(
   pathMiddlewareMap: MiddlewareConfig,
   globalMiddleware?: Partial<
     Record<'before' | 'after', MiddlewareFunction | MiddlewareFunction[]>
   >,
+  config?: NEMOConfig,
 ): NextMiddleware {
   return async (
     request: NextRequest,
@@ -136,10 +158,20 @@ export function createMiddleware(
           }
         },
       });
-      if (middlewareResponse instanceof Response) return middlewareResponse;
+      if (middlewareResponse instanceof Response) {
+        filterHeaders(
+          middlewareResponse as NextResponse,
+          config?.excludedHeaders ?? defaultExcludedHeaders,
+        );
+        return middlewareResponse;
+      }
     }
 
-    return NextResponse.next({ request, headers: request.headers });
+    return NextResponse.next({
+      request: {
+        headers: new Headers(request.headers),
+      },
+    });
   };
 }