I was trying to write a function schema such that specs of second argument are dependent on the value of first argument e.g. first argument can be a :keyword with value :id or :contact-id second argument has to be a :map that needs to contain the key supplied in first argument So far, I have done below:

[:=>
   [:cat
    [:alt [:= :id] [:= :contact-id]]
    [:alt [:map [:id :string]] [:map [:contact-id :string]]]]
   :string]

(defn test-fn
  {:malli/schema =>test-fn}
  [key value]
  (str (name key) "_" (key value)))

(def =>take2
  [:=>
   [:cat
    [:alt
     [:cat [:= :id] [:map [:id :string]]]
     [:cat [:= :contact-id] [:map [:contact-id :string]]]]]
   :string])

(defn test-fn-2
  {:malli/schema =>take2}
  [key value]
  (str (name key) "_" (key value)))