More functional API

[currentoor]

Right now we have a single global -pluck multimethod. This works for now but it's rigid. We can't override a particular key in certain contexts without mutating the behavior everywhere.

Higher order functions would allow more flexibility. Something like

(defmulti pluck-handler
  (fn [k env init-result] k))

(defmethod pluck-handler :default [k env init-result]
  (get init-result k))

(defmethod pluck-handler :data-source/fields [k {db :db} {:keys [data-source/fields-str]}]
  (clojure.edn/read-string fields-str))

(def pluck (adstage.pluck-api/buildpluck-handler-fn
            ;; The subroutine that handles wrapping the pull results.
            :pluck-handler pluck-handler
            ;; Keys the pluck API should wrap.
            :pluckable? (fn [key] (contains? (methods pluck-handler) key))
            ;; Map of pluck API keys to Datomic keys.
            :prepluck-handler  {:data-source/fields :data-source/fields-str}))

(pluck {:db db} [:db/id :data-source/fields] 17592186057566)

;; =>
{:db/id              17592186057566
 :data-source/fields ["spend" "clicks" "ctr"]}

So instead of providing pluck, we provide a pluck factory.

[currentoor]

This would also address #1.

[adstage-david]

This seems like a reasonable idea to me. It's not much different from the sente setup - as long as it's well documented I think it'd work fine.