The every-kv doc states "takes separate key and val preds and works on associative collections". Vectors return true for associative? but do not currently work:
user=> (s/conform (s/every-kv any? any?) [])
[]
user=> (s/conform (s/every-kv any? any?) [1 2 3])
:clojure.spec/invalid
user=> (s/conform (s/every-kv integer? string?) [])
[]
user=> (s/conform (s/every-kv integer? string?) ["x"])
:clojure.spec/invalid
Another similar problem:
(s/explain-data (s/every-kv int? int?) [{:a :b}])
UnsupportedOperationException nth not supported on this type: PersistentArrayMap clojure.lang.RT.nthFrom (RT.java:903)
*Cause:* Vectors should not work with every-kv. The combination of every-kv and every-impl assume that the collection passed to every-kv can provide a seq of map entries. In the explain case, the ::kfn created by every-kv is used to create a better path segment using the key rather than the element index. The kfn assumes that an element of the collection can call `(nth entry 0)` on the element. In the explain failure above, the map {:a :b} will throw when invoked with nth.
*Proposed:* Do the following to be clearer about the requirement that the coll elements are map entries:
* Modify the docstring to say "seqs to map entries" rather than "is a map"
* Modify the kfn to add a check that the element is an entry and if so, use it's key. If not, use the index (of the element itself). In this case, when passed an entry it will report with the actual key but when passed something that's not an entry, it will report the collection based index of the non-entry.
After the patch, the explain-data call will provide a useful error rather than the exception above:
user=> (s/explain-data (s/every-kv int? int?) [{:a :b}])
#:clojure.spec.alpha{:problems ({:path [], :pred vector?, :val {:a :b}, :via [], :in [0]})}
*Patch:* clj-2080-8.patch
