ADR 52: Spec registration is opt-in

Date: 2026-07-02

Supersedes the spec-registration portion of ADR 49.

Context

ADR 49 established that spec registration is opt-in via :clj-zig/spec true, defaulting on at 1.0. The implementation landed in clj-zig.spec-check, which maps every boundary type to a clojure.spec.alpha predicate.

Decision

The spec-for-type function maps each normalized boundary type to a spec form: scalars to int?/double?/boolean?; enums to the member keyword set; named structs to map?; slices to coll-of; optional to nilable; handle to some?; stream to the element spec. Argument specs are permissive (a slice arg accepts any array or collection); return specs are precise.

The register! function evaluates s/def and s/fdef forms to register both the argument and return specs. The :clj-zig/spec true attr-map triggers register! at definition time via requiring-resolve, so clojure.spec.alpha is not a hard dependency of clj-zig.core.

Consequences

Users who opt in get immediate boundary validation. The spec forms use fully-qualified names (clojure.spec.alpha/coll-of) so they resolve correctly in any namespace. The default-on switch at 1.0 is a one-line change.