[Proposal] GoRoute.pageBuilder should be optional if `.routes` has a non-zero length

[esDotDev]

I find I often need to add placeholder builders, simply to satisfy GoRouter, and then add redirects to avoid those empty routes:

Notice the /app and settings routes, they are only there for organization, and is not actually valid destinations:

late GoRouter goRouter = GoRouter(
    routes: [
      GoRoute(path: '/', pageBuilder: (_, __) => const MaterialPage(child: LoginPage())),
      GoRoute(
        path: '/app',
        pageBuilder: (_, __) => const MaterialPage(child: SizedBox.shrink()), // empty page, 
        routes: [
          GoRoute(path: 'inbox', pageBuilder: (_, __) => const MaterialPage(child: InboxPage())),
          GoRoute(
            path: 'settings',
            pageBuilder: (_, __) => const MaterialPage(child: SizedBox.shrink()), // empty page, 
            routes: [
              GoRoute(path: 'general', pageBuilder: (_, __) => const MaterialPage(child: GeneralPage())),
              GoRoute(path: 'accounts', pageBuilder: (_, __) => const MaterialPage(child: AccountsPage())),
              GoRoute(path: 'filters', pageBuilder: (_, __) => const MaterialPage(child: FiltersPage())),
            ],
          ),
        ],
      ),
    ],
  );

Then I have to add redirects, like:

redirect: (state) {
    // redirect away from empty /app route
    if (state.location == '/app' || state.location == '/app/') return '/app/inbox';

    // redirect away from empty /app/settings route
    if (state.location == '/app/settings' || state.location == '/app/settings/') return '/app/settings/general';
  },

It seems like it would be nice if the GoRoute would just use the first pageBuilder found in .routes if it has no builder of its own.

[csells]

You can write that like this, which I think is more clear:

late GoRouter goRouter = GoRouter(
    routes: [
      GoRoute(path: '/', pageBuilder: (_, __) => const MaterialPage(child: LoginPage())),
      GoRoute(
        path: '/app',
        redirect: (s) => '/app/inbox', 
        routes: [
          GoRoute(path: 'inbox', pageBuilder: (_, __) => const MaterialPage(child: InboxPage())),
          GoRoute(
            path: 'settings',
            redirect: (s) => '/app/settings/general', 
            routes: [
              GoRoute(path: 'general', pageBuilder: (_, __) => const MaterialPage(child: GeneralPage())),
              GoRoute(path: 'accounts', pageBuilder: (_, __) => const MaterialPage(child: AccountsPage())),
              GoRoute(path: 'filters', pageBuilder: (_, __) => const MaterialPage(child: FiltersPage())),
            ],
          ),
        ],
      ),
    ],
  );

This is one of the benefits of route-level redirect and there's no need for a top-level redirect.

[esDotDev]

Sorry for the delayed response, this route-level redirect is nice for many use cases, and is preferable to the top level redirect for this use case, but not ideal as we need to repeat a string that is already declared, so it makes another maintenance pt. If any of app, settings or general changes, then this might break, vs the automatic fall-through would just work.