Support :enter and :leave for transformers

[ikitommi]

Currently, the schema-defined transforming functions are all applied before any other transformations. There should be a way to define the order they are run. Interceptors to the rescue?

currently

(m/decode 
  [:and {:decode/string (constantly (partial str "olipa_"))} string?] 
  "kerran" 
  mt/string-transformer)
; "olipa_kerran"

with interceptors

;; function maps to :enter
(m/decode 
  [:and {:decode/string (constantly (partial str "olipa_"))} string?] 
  "kerran" 
  mt/string-transformer)
; "olipa_kerran"

(m/decode
  [:and {:decode/string (constantly {:enter (partial str "olipa_")})} string?]
  "kerran"
  mt/string-transformer)
; "olipa_kerran"

(m/decode
  [:and {:decode/string (constantly {:leave (partial str "_ihminen")})} string?]
  "kerran"
  mt/string-transformer)
; "kerran_ihminen"

(m/decode
  [:and {:decode/string (constantly {:enter (partial str "olipa_")
                                     :leave (partial str "_ihminen")})} string?]
  "kerran"
  mt/string-transformer)
; "olipa_kerran_ihminen"

[ikitommi]

maybe even support multiple interceptors via vector syntax?

(m/decode
  [:and {:decode/string (constantly [str (partial str "id_") #(str % "23") keyword]} keyword?]
  "1"
  mt/string-transformer)
; :id_123