*Problem:*
When attempting to validate a vector containing an optional map, the spec will validate correctly if the vector contains a valid map. If however the optional map does not satisfy the spec misleading error messages are produced. It would be nice if on a partial match of an optional map that some indication of this would be given to the user.
*Example REPL session to illustrate problem:*
The optional nested map (:optional-nested-map) below fails validation because :nested-element-b is a string instead of an int however the explain report says the spec fails at the parent predicate: :user/vector-schema at: [:element-value] predicate: string?.
It would be more helpful for the user in this case if spec reported that the optional nested map at :optional-nested-map had failed due to ::nested-element-b failing the int? predicate.
{code:xml}
user=> (require '[clojure.spec :as s])
nil
user=> (s/def ::nested-element-a string?)
:user/nested-element-a
user=> (s/def ::nested-element-b int?)
:user/nested-element-b
user=> (s/def ::nested-element-schema
(s/keys :opt-un [::nested-element-a ::nested-element-b]))
:user/nested-element-schema
user=> (s/def ::vector-schema
(s/cat :tag-kw #{:tag}
:optional-nested-map (s/? (s/spec ::nested-element-schema))
:element-value string?))
:user/vector-schema
user=> (s/valid? ::vector-schema [:tag {:nested-element-a "bla" :nested-element-b 10} "Element"])
true
user=> (s/valid? ::vector-schema [:tag {:nested-element-a "bla" :nested-element-b ""} "Element"])
false
user=> (s/explain ::vector-schema [:tag {:nested-element-a "bla" :nested-element-b ""} "Element"])
In: [1] val: {:nested-element-a "bla", :nested-element-b ""} fails spec: :user/vector-schema at: [:element-value] predicate: string?
nil
user=>
