tristan-morris

And rust, but they chose to panic on the error condition. Wild.

Oh absolutely, that's how it would have been treated.

Surely a unwrap_or_default() would have been a much better fit--if fetching features fails, continue processing with an empty set of rules vs stop world.

Why call .unwrap() in a function which returns Result<_,_>?

For something so critical, why aren't you using lints to identify and ideally deny panic inducing code. This is one of the biggest strengths of using Rust in the first place for this problem domain.