Does anyone know of an efficient way to generate a multi-spec value with a particular tag? (ie. without doing a such-that and hoping to get lucky)

@codonnell what do you mean by a multi-spec value? have an example?

If i run a stest/check and hit an error, how do i inspect the value that was generated? my return value is a function. I fspecced it, and one of the inputs to that function, generated during stest/check is causing the spec to fail

@ackerleytng

(s/def ::type #{::a ::b})
(s/def ::a-value pos-int?)
(s/def ::b-value keyword?)

(defmulti mymap-type ::type)
(defmethod mymap-type ::a [_]
  (s/keys :req [::type ::a-value]))
(defmethod mymap-type ::b [_]
  (s/keys :req [::type ::b-value]))
(s/def ::mymap (s/multi-spec mymap-type ::type))
;; How to generate a mymap value with tag ::a here without using gen/such-that

something like this?

(s/conform ::mymap {::type ::a
                    ::a-value 1})
(s/conform ::mymap {::type ::b
                    ::b-value :foo})

(map (partial s/explain-data ::mymap)
     (gen/sample (tgen/let [type_ (gen/elements [::a ::b])
                            a-value tgen/pos-int
                            b-value (gen/keyword)]
                   (conj {::type type_} 
                         (if (= type_ ::a)
                           {::a-value (inc a-value)}
                           {::b-value b-value})))))

tgen is clojure.test.check.generators

[clojure.spec.gen.alpha :as gen]

pos-int generates 0 sometimes, hence the inc

this talk was super helpful for me https://www.youtube.com/watch?v=F4VZPxLZUdA

s-pos-int doesn't generate zeros, fyi

I'd prefer not to build up the value manually like that, since the actual spec I'm working with is much more complex than the toy example I posted above.

I'll definitely check out that talk, thanks.

@gfredericks thanks for giving that talk!! I loved the pictures too

@codonnell hmm...

@codonnell (gen/sample (s/gen ::mymap {::type #(gen/return ::a)}))

It would have been, but there is a bug with providing a generator for the dispatch key - See my bug report and patch https://dev.clojure.org/jira/browse/CLJ-2311

thanks @andreas862, that is exactly what I was looking for. Hopefully your patch is accepted!