Let users register their own extension functions?

[luxas]

Category

Cedar language or syntax features/changes

Describe the feature you'd like to request

For some use-cases, it'd be nice to extend the language with evaluator/authorizer-specific your own extension functions. For example,

• for transpiling another policy language's unsupported features into a Cedar-compatible form, to make use of TPE and symcc, even though the latter might give false positives Maybe define a Cedar <-> CEL interface through Cedar extension functions upbound/kubernetes-cedar-authorizer#45
• for performing compound authorization (Compound authorization #2123), like Kubernetes' authorizer function

I didn't look too closely to see how feasible it is to already add your own extensions already today (it might even work when using primitives from cedar-policy-core only?), but this issue is made to track interest in considering this as a core feature (AFAIK, this is not a "supported" use-case today)

Describe alternatives you've considered

Advanced users might just want to use cedar-policy-core (if it already works there), or carry a Cedar fork (not preferable) which adds their own extensions to ALL_AVAILABLE_EXTENSIONS.

Additional context

No response

Is this something that you'd be interested in working on?

• 👋 I may be able to implement this feature request
• ⚠️ This feature might incur a breaking change