Hi. I've noticed that CLJS impl of explain prints more stuff than Clojure. Is it on purpose? CLJS:

=>  (s/explain ::x 23)
val: 23 fails spec: :cljs.user/x predicate: string?
:cljs.spec.alpha/spec  :cljs.user/x
:cljs.spec.alpha/value  23

=>  (s/explain ::x 23)
val: 23 fails spec: :cljs.user/x predicate: string?

If I would like instrument to check my specs, what would be the preferred way of spec:ing a multimethod? Can I use a multispec with the same dispatch fn or do I need an indirection fn with a spec in each defmethod?

You can make the defmulti dispatch function explicit and spec that

@kenny I wonder if qualified symbols can be replaced like this:

(case form-sym
      (clojure.spec.alpha/keys
        cljs.spec.alpha/keys) ...
;=>

    (case form-sym
      `s/keys ...

given you already required [clojure.spec.alpha :as s]

then, getting rid of alpha would be just 1 line :require update

I recall that spec was inspired in part by RDF. Is there any recommended way for describing XML structures?

xml represented by what data structure?

I'm using clojure.data.xml, so whatever that uses internally.

Its sexp-as-element is the closest I've seen it get to simple data structures, but even that seems to be pretty complex to spec

seems pretty straightforward?

I'm afraid I don't follow

there are at least two formats there - the input and output of sexp-as-element. they both seem pretty straightforward to spec if you want to

the output's clojure.data.xml.Elements, right?

Element is a defrecord, so you can just spec it as a map with 3 known keys

the sexp form is just structured vectors and can be spec’ed with s/cat etc

oh, there actually are specs already in data.xml

really?

https://github.com/clojure/data.xml/blob/master/src/main/resources/clojure/data/xml/spec.cljc

that’s for the element forms

it's not in the stable release yet though, is it?

i see you bumped its clojure dependency up to 1.9 when specs were introduced

as you pointed out i can just spec them as maps with :tag :attrs and :content

if I want to declare a with-gen ::spec generator-fn, generator fn needs to be a fn that returns a generator. how does one create a generator that’s simply a function, without using fmap or any of the other test.check.generators?

for example I just want a “generator” that invokes (random-uuid) where the fn itself is already random and doesn’t need any randomness from the generator scaffolding

i had some garbage like

(s/exercise ::p/id 10 {::p/id (fn [] (gen/fmap #(random-uuid) (s/gen (s/int-in 1 10))))})

maybe (gen/return .. ) ?

(gen/return (random-uuid)) maybe?

https://clojure.github.io/test.check/generator-examples.html

(def int-or-nil (gen/one-of [gen/int (gen/return nil)]))
(gen/sample int-or-nil)
;; => (nil 0 -2 nil nil 3 nil nil 4 2)

thats using gen/return to always return nil

I'm not entirely sure its what you are looking for though 😞

that seems like the same idea as abusing fmap and an existing gen (int-in), but with different fns. it just feels like there’s a built-in fn like gen/return for this use case, right?

using external sources of randomness prevents shrinking and repeatability so is discouraged

if you want to do the discouraged thing, fmap will work and return won't.