(apologies for the resend; this didn't reach the web interface the first
time around)
When I have a function whose arguments I have spec'ed with an fdef, and
that function is used in the construction of a lazy seq, it's easy to
stumble into situations where the arguments are not actually checked even
when the function is instrumented.
Here's a contrived example: (using [org.clojure/clojure "1.9.0-RC1"]
[org.clojure/spec.alpha "0.1.143"])
(require '[clojure.spec.alpha :as s])
(require '[clojure.spec.test.alpha :as st])
(s/fdef add1 :args (s/cat :x int?))
(defn add1 [x]
(+ x 1))
(st/instrument [`add1])
(add1 1) ;; => 2
(add1 "1") ;; => spec error for args to add1
(s/fdef print-coll-with-banner
:args (s/cat :banner string?
:xs (s/coll-of any?)))
(defn print-coll-with-banner [banner c]
(println banner)
(println c))
(print-coll-with-banner "hello adding world" (map add1 [1 2 3]))
;; => prints some stuff
(print-coll-with-banner "hello adding world" (map add1 [1 2 "3"]))
;; => spec error for args to add1
(st/instrument [`print-coll-with-banner])
(print-coll-with-banner "hello adding world" (map add1 [1 2 "3"]))
;; => ClassCastException inside of add1
This appears to be happening because the lazy sequence is actually realized
*by* spec when instrumentation is on, but at that point checking is
actually disabled with the st/with-instrument-disabled macro.
A few questions:
* Is this the intended behavior?
* The code in question has been there as far back as I can trace it in git.
What is this check trying to guard against?
* Does the fact that I got into this situation indicate that I'm doing
something wrong? (The above code is clearly contrived, but I did run into
this in a real program)
- Russell
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