Is there any way within a query to propagate the current rule environment (`%`) into it? I am frequently in a situation where I need a subquery for an existence check (i.e. “any of these values may match”) but need a rule in the subquery. E.g. a rule like

[(rule-any-matches ?e ?test-values)
 [(q '[:find ?e
       :in $ [?test-value ...]
       :where (some-other-rule ?e ?test-value)] $ ?test-values) [[?_ignored]]]]

My google-fu seems to be failing me. Does anyone happen to know where in the docs the behavior of a pull reverse lookup + isComponent=true + cardinality=one is specified as returning the result not in a vector? e.g.,

;; schema 
{:db/ident       :not-a-component
 :db/cardinality :db.cardinality/one
 :db/valueType   :db.type/ref}
{:db/ident       :a-component
 :db/cardinality :db.cardinality/one
 :db/valueType   :db.type/ref
 :db/isComponent true}

(d/pull db
        '[{:_not-a-component [:title]}]
        [:id "a"])
=> {:_not-a-component [{:title "foo"}]}

(d/pull db
        '[{:_a-component [:title]}]
        [:id "a"])
=> {:_a-component {:title "foo"}}