skjema

Fast JSON Schema 2020-12 validation for Clojure. skjema is Norwegian for schema.

com.blockether/skjema {:mvn/version "0.2.0"}

Use

(require '[com.blockether.skjema.core :as skjema])

(def schema
  (skjema/read-schema (java.nio.file.Path/of "user.schema.json" (make-array String 0))))

(def validator (skjema/compile-schema schema))

(skjema/valid? validator {"name" "Ada"})
;; => true

(skjema/validate validator {"name" 42})
;; => {:valid false
;;     :errors [{:instanceLocation "/name"
;;               :keywordLocation "/properties/name/type"
;;               :keyword "type"
;;               :params {:type "string"}
;;               :error "expected string, got integer"}]}

read-schema accepts JSON text, Path, File, URL/classpath resource, InputStream, or Reader. write-schema returns compact JSON text. Both use charred.

Compile once when a schema is reused. References are resolved from an explicit registry; skjema never fetches them:

(def validator
  (skjema/compile-schema schema
    {:base "https://example.com/user.json"
     :registry {"https://example.com/tag.json" tag-schema}
     :format-assertion true}))

Errors

validate returns JSON Schema BASIC output locations and adds keyword, keyword-specific params, and a human-readable error. A successful result is {:valid true}. Parsing, compilation, and writing throw ExceptionInfo with a :skjema/error category and preserve the original cause.

Verification

The suite covers all required and optional draft 2020-12 cases from the official JSON-Schema-Test-Suite. Java owns the compiled validation and IDN hot loops; Clojure owns complete evaluation and structured errors.

clojure -M:test
clojure -M:bench

The benchmark prepares both schemas before timing validation. Run it on the machine and JVM that matter to your workload.

License

MIT — see LICENSE and NOTICE.