I'm sure this is a well known issue, but I've not found much written about
it online.
In the spec guide, we have this example of spec'ing a function
(s/fdef ranged-rand
:args (s/and (s/cat :start int? :end int?)
#(< (:start %) (:end %)))
...)
This form, an s/cat within an s/and, is going to be a standard pattern
whenever you want to express some cross-argument constraint. It will be
common to use keyword references to specs
(s/fdef f
:args (s/and (s/cat :arg1 ::foo, :arg2 ::baa)
#(... constraint expr ...)
...)
The problem is that the constraint expression has to work on conformed
versions of the args, not the simple values passed by the caller, and so is
tightly coupled to the implementation of ::foo and ::baa, and liable to
break when those specs change.
There is s/unform, but I've found it to not work in all cases, e.g.
(->> [1 2 "blah"]
(s/conform (s/coll-of (s/or :i integer? :s string?)))
(s/unform (s/coll-of (s/or :i integer? :s string?))))
=> [[:i 1] [:i 2] [:s "blah"]]
If I am understanding correctly, I should get the original vector there.
Aside from this problem, it would be a bit cumbersome to have to unform
everything in those preconditions.
Any insight appreciated!
Tom
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