Is there a way to not include a key when using s/coll-of + kind map? + conform-keys true? For example,

(s/conform
  (s/coll-of
    (s/and (s/tuple #{"a"} boolean?)
           (s/conformer (fn [[_ v]] nil)))
    :kind map?
    :conform-keys true)
  {"a" true})
=> {nil nil}

no way to do that

in general, use of conformers to do arbitrary transforms is considered an anti-pattern (conformer really exists for building new spec types primarily)

Yep - definitely in a gray area. Thanks.