ShaderGraph creating blank shaders

I’ve been working with ShaderGraph for the last few days and have made a few shaders. I’ve been following various tutorials, but now ShaderGraph seems to create blank shaders that don’t have a preview and don’t make a working material.

Take for example this toon shader where I’m following this tutorial https://www.patreon.com/posts/converting-some-24781996:

It should look something like this:

But it looks like this:

No previews in the nodes and no main preview (and not shown here: no effect on a material or the object the material is used by).

Even a super simple one is duff:

I have had working shaders from ShaderGraph, but now all of the ones I try are like this: lots of nodes and trees, but the previews are blank and the shader has no effect on the scene.

Any ideas what this is? Or how to troubleshoot it?

We’ve had a few issues with the preview shader so far. Please file a bug here: Unity QA: Building quality with passion
This way we can check if this is an ongoing issue or one that’s already been fixed.