multi-spec
- (multi-spec mm retag)
Takes the name of a spec/predicate-returning multimethod and a tag-restoring keyword or fn (retag). Returns a spec that when conforming or explaining data will pass it to the multimethod to get an appropriate spec. You can e.g. use multi-spec to dynamically and extensibly associate specs with 'tagged' data (i.e. data where one of the fields indicates the shape of the rest of the structure). (defmulti mspec :tag) The methods should ignore their argument and return a predicate/spec: (defmethod mspec :int [_] (s/keys :req-un [::tag ::i])) retag is used during generation to retag generated values with matching tags. retag can either be a keyword, at which key the dispatch-tag will be assoc'ed, or a fn of generated value and dispatch-tag that should return an appropriately retagged value. Note that because the tags themselves comprise an open set, the tag key spec cannot enumerate the values, but can e.g. test for keyword?. Note also that the dispatch values of the multimethod will be included in the path, i.e. in reporting and gen overrides, even though those values are not evident in the spec.
© Rich Hickey. All rights reserved. Eclipse Public License 1.0
2 Examples
Use retag function to allow generative testing of multi-spec whose multimethod has a :default dispatch method. (require '[clojure.spec.alpha :as s] '[clojure.spec.gen.alpha :as gen]) (s/def ::tag #{:a :b :c :d}) (s/def ::example-key keyword?) (s/def ::different-key keyword?) (defmulti tagmm :tag) (defmethod tagmm :a [_] (s/keys :req-un [::tag ::example-key])) (defmethod tagmm :default [_] (s/keys :req-un [::tag ::different-key])) (s/def ::example (s/multi-spec tagmm :tag)) (gen/sample (s/gen ::example)) ;=> only get examples with :tag :a (s/def ::example (s/multi-spec tagmm (fn retag [gen-v dispatch-tag] gen-v))) (gen/sample (s/gen ::example)) ;=> get examples with all :tag options
(def create-playlist (s/cat :command ::commands :type ::types :data (s/coll-of ::playlist))) (def create-song (s/cat :command ::commands :type ::types :data (s/coll-of ::song))) (def create-user (s/cat :command ::commands :type ::types :data (s/coll-of ::user))) (defmulti create-spec? second) (defmethod create-spec? :playlist [_] create-playlist) (defmethod create-spec? :song [_] create-song) (defmethod create-spec? :user [_] create-user) (def update-playlist (s/cat :command ::commands :type ::types :data (s/coll-of ::playlist-update))) (def update-song (s/cat :command ::commands :type ::types :data (s/coll-of ::song-update))) (def update-user (s/cat :command ::commands :type ::types :data (s/coll-of ::user-update))) (defmulti update-spec? second) (defmethod update-spec? :playlist [_] update-playlist) (defmethod update-spec? :song [_] update-song) (defmethod update-spec? :user [_] update-user) ;; [:create :user [{:name "bobby"} {:name "sally"}{:name "fred"}]] (s/def ::create-action (s/with-gen #(s/multi-spec create-spec? %) #(gen/fmap vec (s/gen create-action-pattern)))) ;; [:update :user ["1"] [{:name "bobby minerva"}]] (s/def ::update-action (s/with-gen #(s/multi-spec update-spec? %) #(gen/fmap vec (s/gen update-action-pattern)))) ;; examples => (s/explain ::create-action [:create :user [{:name "bobby"} {:name "sally"}{:name "fred"}]]) Success! nil => (s/explain ::update-action [:update :user ["1"] [{:name "bobby minerva"}]]) Success! nil