Missing shader variants

Hi all,

I'm building some materials at runtime in my Unity project, and I have (most of) the variants in a .shadervariants file.

However, sometimes it happens that I hit a path where I create a material with a shader variant that I hadn't included in the .shadervariants file, and the model is rendered as black.

1) Is there a way to detect that this happened? i.e. a way to detect, at runtime, that a particular shader variant was not found and that a fallback is being used.
2) Is there a way to, at runtime, compile/create a shader variant which wasn't included at compile time for your project?

Thanks!