Svelte SSR issues (re-render on hydration, head duplication)

Svelte
1

Hi, I have issues with SSR in Svelte.

  1. Flashing of the content - first, the page gets loaded really fast via SSR, then everything disappears in order to appear again (nothing changes from the the initial SSR version). When client-routing, it only happens on the first load, then the client router handles updates without this flashing. I found mentions of such problems for React and Vue (but it might not be the same thing). Is there a solution to it so it doesn’t flash?

  2. I have to have two ways to load data for components - depending on whether it is loaded on the server or client. Is that necessary?

<script>
  $m: {
    // guard subscriptions as they are not available on the server
    if (Meteor.isClient) Meteor.subscribe("links.all")
  }
  
  let links
  if (Meteor.isServer) {
    links = LinksCollection.find().fetch() // initially SSR-load data
  }
  // or wait for the subscription on the client, it will not finish within SSR
  $m: links = LinksCollection.find().fetch();
</script>
  1. Head data gets duplicated - SSR pushes its version, then hydration duplicates it again. I need SSR head data for SEO. But I also need to at least to change titles on client navigation (while the other SSR-related entries linger in the head incorrectly; but those are generally not crucial for users). It might be just a Svelte bug though Issues · sveltejs/svelte · GitHub

A repo where you can see the flashing (the <H1> is different to make it more noticeable) and duplicated entries in <head>.