If you want the map to be empty, you could make it closed:

(m/validate [:map {:closed true}] {})
;; => true

(m/validate [:map {:closed true}] {:a :b})
;; => false

If you don't, it will just validate any map, not imposing the need for it to be empty

Not sure about the transformers part, though.

Sorry, I left it out because It doesn’t make any difference. (malli.core/encode [:or [:map {:closed true} [:id :uuid] [:name :string] [:age :int]] [:map {:closed true}]] {:id (random-uuid) :name "john" :age 15} malli.transform/json-transformer) => {:id #uuid "e707c673-61c3-42f6-b5ad-94b6d42dfe73", :name "john", :age 15} and (malli.core/encode [:map {:closed true} [:id :uuid] [:name :string] [:age :int]] {:id (random-uuid) :name "john" :age 15} malli.transform/json-transformer) => {:id "d9073882-8310-426f-85c9-c8263569b37f", :name "john", :age 15} In second case, the UUID get’s transformed

For me it results in the same (json-encoded) value:

(malli.core/encode [:or
                    [:map {:closed true} [:id :uuid] [:name :string] [:age :int]]
                    [:map {:closed true}]]
                   {:id (random-uuid) :name "john" :age 15}
                   malli.transform/json-transformer)
;; => {:id "b1c74ece-f881-4a8f-8a19-a572a7a4d1bc", :name "john", :age 15}

(malli.core/encode [:map {:closed true} [:id :uuid] [:name :string] [:age :int]] {:id (random-uuid) :name "john" :age 15}
                   malli.transform/json-transformer)
;; => {:id "defafe57-e589-4e7b-9e57-ea9fe413f3bb", :name "john", :age 15}

(modulo the UUID being different, of corse)

Just to check, which version of Malli are you running?

0.11.0

i am on old version probably, thanks for head up. I will try to upgrade.

Not sure if it's that (I ran this on 0.12), but the exact code you had pasted worked for me. Maybe try upgrading, just in case

Yeah, it was really the old version 🙂!

Awesome! Glad it's sorted 🙂

Something like this?

(m/validate
  (m/schema
    [:schema {:registry {"top-level"
                         [:multi {:dispatch :type}
                          [:one
                           [:map
                            [:type [:= :one]] 
                            [:one-prop :string]
                            [:children {:optional true} [:vector [:ref "top-level"]]]]]
                          [:two
                           [:map
                            [:type [:= :two]]
                            [:two-prop :int]
                            [:children {:optional true} [:vector [:ref "top-level"]]]
                            ]]]}}
     [:ref "top-level"]]
    )
  {:type :one :one-prop "hi" :children [{:type :two :two-prop 400}]})