可能修订 spec.alpha2 中 s/merge 的行为

Question

以下示例显示，您可以使用 mult-specs 从 s/merge 中获取生成的值，这些 mult-specs 在预期的 spec 中不一定有意义。

查看 s/merge 生成器的实现时，s/merge 的每个参数都会单独生成，但如果没有从右到左流动，则像多 specs 这样的选择将不会从它们的分配中随机选择。

  (s/def :ent/id string?)

  (defmulti ent-multi-id :ent/id)
  (defmethod ent-multi-id :default [_] (s/keys))

  (defn maybe-retag-fn [retag-k]
    (fn [gen-v dispatch-tag]
      (if (= dispatch-tag :default)
        gen-v
        (assoc gen-v retag-k dispatch-tag))))

  (s/def ::ent (s/merge (s/multi-spec ent-multi-id (maybe-retag-fn :ent/id))
                        (s/keys :req [:ent/id])))

  (gen/sample (s/gen ::ent) 5)
  ;; => ({:ent/id ""} {:ent/id "w"} {:ent/id ""} {:ent/id "66"} {:ent/id "63v"})

  (s/def :foo/id string?)

  (defmethod ent-multi-id "foo" [_]
    (s/keys :req [:foo/id]))

  (gen/sample (s/gen ::ent) 5)
  ;; => ({:foo/id "", :ent/id ""} {:foo/id "6", :ent/id "f"} {:foo/id "A", :ent/id "W"} {:foo/id "L", :ent/id "nd"} {:ent/id "H"})