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Data Specs

(require '[ :as ds])

Data Specs offers an alternative, Schema-like data-driven syntax to define simple nested collection specs. Rules:

  • Just data, no macros
  • Can be transformed into vanilla specs with valid forms (via form inference)
  • Supports nested Maps {}, Vectors [] and Sets #{}
    • Vectors and Sets are homogeneous, and must contains exactly one spec
  • Maps have either a single spec key (homogeneous keys) or any number keyword keys.
    • With homogeneous keys, keys are also conformed
    • Map (keyword) keys
      • can be qualified or non-qualified (a qualified name will be generated for it)
      • are required by default
      • can be wrapped into ds/opt or ds/req for making them optional or required.
    • Map values
      • can be functions, specs, qualified spec names or nested collections.
  • wrapping value into ds/maybe makes it s/nilable

NOTE: to avoid macros, current implementation uses the undocumented functional core of clojure.spec.alpha: every-impl, tuple-impl, map-spec-impl, nilable-impl and or-spec-impl. Support for spec-alpha2 should help to remove these.

NOTE: To use enums with data-specs, you need to wrap them: (s/spec #{:S :M :L})

(s/def ::age pos-int?)

;; a data-spec
(def person
  {::id integer?
   ::age ::age
   :boss boolean?
   (ds/req :name) string?
   (ds/opt :description) string?
   :languages #{keyword?}
   :aliases [(ds/or {:maps {:alias string?}
                     :strings string?})]
   :orders [{:id int?
             :description string?}]
   :address (ds/maybe
              {:street string?
               :zip string?})})

;; it's just data.
(def new-person
  (dissoc person ::id))

To turn a data-spec into a Spec, call ds/spec on it, providing either a options map or a qualified keyword describing the root spec name - used to generate unique names for sub-specs that will be registered. Valid options:

Key Description
:spec The wrapped data-spec.
:name Qualified root spec name - used to generate unique names for sub-specs.
:keys-spec Function to wrap not-wrapped keys, e.g. ds/opt to make keys optional by default.
:keys-default Function to generate the keys-specs, default ds/keys-specs.
;; options-syntax
(def person-spec
    {:name ::person
     :spec person}))

;; legacy syntax
(def person-spec
  (ds/spec ::person person))

(def new-person-spec
  (ds/spec ::person new-person))

The following specs are now registered:

(keys (st/registry #"user.*"))
; (:user/id
;  :user/age
;  :user$person/boss
;  :user$person/name
;  :user$person/description
;  :user$person/languages
;  :user$person$aliases$maps/alias
;  :user$person/orders
;  :user$person$orders/description
;  :user$person$orders/id
;  :user$person/address
;  :user$person$address/street
;  :user$person$address/zip)

And now we have specs:

  {::age 63
   :boss true
   :name "Liisa"
   :languages #{:clj :cljs}
   :aliases [{:alias "Lissu"} "Liisu"]
   :orders [{:id 1, :description "cola"}
            {:id 2, :description "kebab"}]
   :description "Liisa is a valid boss"
   :address {:street "Amurinkatu 2"
             :zip "33210"}})
; true

All generated specs are wrapped into Specs Records so transformations works out of the box:

  {::age "63"
   :boss "true"
   :name "Liisa"
   :languages ["clj" "cljs"]
   :aliases [{:alias "Lissu"} "Liisu"]
   :orders [{:id "1", :description "cola"}
            {:id "2", :description "kebab"}]
   :description "Liisa is a valid boss"
   :address nil}
; {::age 63
;  :boss true
;  :name "Liisa"
;  :aliases [{:alias "Lissu"} "Liisu"]
;  :languages #{:clj :cljs}
;  :orders [{:id 1, :description "cola"}
;           {:id 2, :description "kebab"}]
;  :description "Liisa is a valid boss"
;  :address nil}

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