Creating an exception to "common" components using single-spa-layout

[raihle]

Describe the bug or question
Does / could single-spa-layout support exceptions to otherwise common components?

To Reproduce
I have an app like this:

<single-spa-router>
  <application name="navigation"></application>
  <route path="app-1">
    <application name="app-1"></application>
  </route>
  <!-- ... -->
</single-spa-router>

I want navigation to be present on "all" routes, but there are specific exceptions. This is pretty easy to implement with the application's underlying activity function, but can I access that while using single-spa-layout?

Additional context
I'm doing server-side rendering, otherwise I would probably just drop the layout engine and rely on manual registration.

[joeldenning]

Hi @raihle, good question. Are the exceptions route based? If so, this is possible by putting the <application> underneath <route>. The <route default> can also be helpful here.

If the exceptions are not route-based, this is possible for browser-only usage of single-spa-layout, since the application objects are returned from constructApplications and can be modified however you'd like:

import { constructRoutes, constructApplications, constructLayoutEngine } from 'single-spa-layout';
import { registerApplication, start } from 'single-spa';

const routes = constructRoutes({...})
const applications = constructApplications({...});
const layoutEngine = constructLayoutEngine({...});

const navigationApp = applications.find(app => app.name === 'navigation')
navigationApp.activeWhen.push((location) => shouldNavigationMount(location))

applications.forEach(registerApplication)
start()

However, on the server side there are no application objects, and no existing way to render applications based on anything except routes. I'm open to that being added to sendLayoutHTTPResponse somehow, but it doesn't currently exist.

[raihle]

Thanks for your reply!

I see now that I can nest additional routes inside <route default>, which allows me to use a top-level default for applications that include the common components, and a lower-level one for the "404" fallback. Thanks again!