Middleware not redirecting server function invocations

[gmoniava]

I stumbled this situation in Nextjs App router. I have middleware which inside has following code:

      // If user is on protected route and has no session redirect to login page.
      if (isProtectedRoute && !session) {
        return NextResponse.redirect(new URL("/login", req.nextUrl));
      }

This normally works e.g. when navigating from URL.

Now, when I arrive at the above middleware when a server function is invoked, the redirect does not happen (although it enters inside if) and also the server function which trigerred this middleware call is not invoked returning undefined. See below:

      startTransition(async () => {
          // Invoke the server function, this triggers middleware too - and inside middleware redirect is called
          // but redirect does not happen and the addMovie never gets called, returns undefined here
          const result = await addMovie(data);

          // Then due to result being undefined I get error here
          setMessage(result.error ? result.error : result.data);
        });

Is this normal behavior? What options do I have in such situation?

Checking session in server function won't change anything here because like I said server function does not get invoked due to middleware.

This is related. I think they suggest there to not handle the server functions in middleware, but then question comes, how to know from middleware if this is a server function or not? IMHO server functions don't start with "api" to check that as one user suggested.

EDIT: it seems in above link the suggestion checks header instead of "api" to bypass server functions in middleware. I will verify that solution when I get to PC and close this if that works.

[gmoniava]

It seems answer is this (from the gh link I mentioned):

export const config = {
  matcher: [
    /*
     * Match all request paths except for the ones starting with:
     * - api (API routes)
     * - _next/static (static files)
     * - _next/image (image optimization files)
     * - favicon.ico (favicon file)
     */
    {
      source:
        '/((?!api|_next/static|_next/image|media|fonts|favicon.ico|favicon.png).*)',
      missing: [
        // Exclude Server Actions
        { type: 'header', key: 'next-action' },
      ],
    },
  ],
};

Somehow I thought initially it was using "api" check to exclude server functions from middleware but I was wrong.