I’m having trouble generating from a recursive spec, I keep hitting StackOverflowError. Are there any docs/guides on how to do that?

I’m doing:

(s/def ::a a?)
(s/def ::b b?)
(s/def ::c (s/with-gen c? (gen/fmap #(make-c %) (s/or :a ::a :b ::b :c ::c)))

I’ve also tried t.c.gen/recursive-gen

hard to say because the example is missing several definitions but you could try (binding [s/*recursion-limit* 1] ...)

That helped, in that gen/sample occasionally finishes, but still stackoverflows some of the time. It surprised me that in the first 10 items, it produces nested c’s 5 deep, which I wouldn’t expect with a recursion limit of 1

yeah I think there’s been a JIRA ticket w/some discussion about this, can’t find it at the moment

https://dev.clojure.org/jira/browse/CLJ-1978

@arohner also this discussion https://clojurians-log.clojureverse.org/clojure-spec/2016-08-17.html#inst-2016-08-17T19:58:22.002442Z

I think I can work around it using gen/frequency

i.e. (gen/frequency [[9 (s/or :a ::a :b ::b)] [1 (s/or :a ::a :b ::b :c ::c]])

frequency helps, but doesn’t completely solve the problem

A transcript of a 2-hour talk by Rich Hickey from Dec 2016 about clojure.spec is up now: https://github.com/matthiasn/talk-transcripts/blob/master/Hickey_Rich/ClojureSpec.md

It doesn't go deep into the details -- more of an intro, and big picture of ways the pieces of spec can be used.