I don't know how to do that without the dreaded :fn schema, unless you make them distinct ranges, e.g.:

[:tuple [:int {:min 0 :max 10}] [:int {:min 10 :max 20}]]

I do not have any ranges, just val needs to be <=max in [val max]

I am having this val-max vector in my videogame for damage [min-max] or hitpoints [current-max].

Maybe writing a custom 'type' ?

Maybe...? The only other thing I can think of is:

[:and [:tuple [:int {:min 0}] [:int {:min 0}]] [:fn (fn [[a b]] (<= a b))]]

But I gather :fn schemas are discouraged, and best avoided if you can find a different solution.

Why are they discouraged? I am new to malli haven't used it before.

It would be nice to have a type :val-max because I am using the same schema at hp/mana/damage

I haven't used Malli that much either, and can't really answer why they're discouraged. But I've seen that mentioned a few times in this channel.

Here's another example that is an actual vector of two elements:

[:and [:vector {:min 2 :max 2} [:int {:min 0}]] [:fn (fn [[a b]] (<= a b))]]

[:and ... [:fn ...]] is "bad" because it's opaque. you get a message that it failed because of the function and nothing else

but if you add in an :error/fn metadata, you can customize

[:fn {:error/fn (fn [{[a b] :value} _]
                  (when (< b a)
                    (format "Expected a (%d) to be smaller than b (%d)" a b)))}
 (fn [[a b]] (<= a b))]

you could use fnil to avoid this issue

i believe the issue comes from https://github.com/metosin/malli/blob/6f454709fd240913faa5eef9a56b6ef740547f77/src/malli/core.cljc#L679where there's no try/catch, just calling the given validator function (`pos?`) on the input (`nil`), which will result in a thrown exception in both clojure and malli

many of the Clojure built-its fail with nil. We could wrap ’em all with m/-safe-pred

For Vars, could add mx/defschema that adds the Var symbol and namespace into the schema as schema properties. Either separate or combined into a new key. so:

(ns my-domain
  (:require [malli.experimental :as mx]))

(mx/defschemas Size [:enum "S" "M" "L"])

;; 1) separately, like Plumatic has (as metadata)
[:enum {:name 'Size
        :namespace 'my.domain} "S" "M" "L"]

;; 2) concatenated into name, property name??
[:enum {:id 'my.domain/Size} "S" "M" "L"]
[:enum {:ref 'my.domain/Size} "S" "M" "L"]
[:enum {:name 'my.domain/Size} "S" "M" "L"]

The problem with plumatic style is that things like json schema generation dereference it recursively instead of lifting it to definitions because schemas are passed by value

For var style, add an option to pass vars as schemas as reference?

I think if we just add the full Var symbol into properties, we can see “this is a my-domain.User instead of an value.

so, referencing to a schema would inline the value, but with data saying what was it all about.

but, we need some way to reference to support recursion, maybe just use Vars like Schema does?

would be natural way for “just a reference”

Yes, and will also provide legible swagger API results for complex domain schemas

(mx/defschema User
  [:map
   [:id :uuid]
   [:name :string]
   [:address #'Address] ;; a reference
   [:friends [:set [:ref #'User]]]) ;; recursion

making a Var a valid reference type makes sense. Already added qualified symbols.