I am a huge fan of Plumatic Schema, and it regularly helps me to find
mistakes in my code early in the development process. However, I just
tracked down a very unexpected error when using a lazy infinite list such
as that produced by `(range)`
Suppose you define two simple functions like `clojure.core/first`. One
doesn't use Schema and the other does:
(defn show-1
[arg]
(nth arg 0))
(s/defn show-2 :- s/Any
[arg :- [s/Any] ]
(nth arg 0))
(nl) (println "show-1")
(spyx (mapv show-1 [ [:a :b :c] (range) ]))
(nl) (println "show-2")
(spyx (mapv show-2 [ [:a :b :c] (range) ]))
The results of running this code are:
show-1
(mapv show-1 [[:a :b :c] (range)]) => [:a 0]
show-2
ERROR in (dotest-line-472) (Iterate.java:54)
Uncaught exception, not in assertion.
expected: nil
actual: *java.lang.OutOfMemoryError*: Java heap space
at clojure.lang.Iterate.next (Iterate.java:54)
clojure.lang.RT.next (RT.java:706)
...
Apparently, turning on Schema validations causes the input collection to be
realized for `show-2` function call.
I am generally not a big fan of (infinite) lazy seq's and don't use them
much. However, this one came up during a simple unit test and really had me
scratching the old noggin for quite a while.....
I'm not sure if there is an easy way of enhancing Schema to avoid this
problem, or if it is just something one needs to be wary of.
Alan
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