custom-builtin-functions

Custom builtin functions for OPA/Rego are created by implementing a Go function with a Decl signature, registering it via init auto-registration under the chainloop namespace, and calling it from your *.rego policies. This extends Rego's policy evaluation with domain-specific logic like chainloop.my_function(input).

Registering a custom builtin requires a Go implementation with proper Decl signature, initialization code for auto-registration, a Description field, error handling, and BuiltinContext support for timeout and cancellation within the chainloop namespace.

Yes. After registering a custom builtin function in Go with proper init registration, you invoke it directly in *.rego files as chainloop.my_function(input) to compute results or enforce policy rules with domain-specific logic.

Custom builtins support error handling through proper error messages and BuiltinContext, which enables timeout and cancellation mechanisms to safely manage policy evaluation and prevent runaway executions.

Custom builtins move complex domain logic into compiled Go functions, enabling performance-critical operations and capabilities unavailable in Rego alone. Policy rules then call these builtins to enforce rules without reimplementing logic in Rego.