Transducer debug

sample.clj

(ns sample
  (:require [clojure.pprint :refer [pprint]]))

(def tap-fn
  pprint)

(add-tap #'tap-fn)

(defn xdebug [xf]
  (fn [rf]
    (let [f (xf rf)]
      (fn
        ([]
         (tap> {:init {}})
         (f))
        ([acc]
         (tap> {:complete {:acc acc}})
         (f acc))
        ([acc value]
         (tap> {:step (array-map :acc acc :value value)})
         (f acc value))))))

(def xf
  (xdebug (map inc)))

(into [] xf (range 5))
;; => [1 2 3 4 5]
;; prints:
;; {:step

(sequence xf (range 5))
;; => (1 2 3 4 5)
;; prints:
;; {:step {:acc nil, :value 0}}
;; {:step {:acc nil, :value 1}}
;; {:step {:acc nil, :value 2}}
;; {:step {:acc nil, :value 3}}
;; {:step {:acc nil, :value 4}}
;; {:complete {:acc nil}}

(transduce xf + (range 5))
;; => 15
;; {:step {:acc 0, :value 0}}
;; {:step {:acc 1, :value 1}}
;; {:step {:acc 3, :value 2}}
;; {:step {:acc 6, :value 3}}
;; {:step {:acc 10, :value 4}}
;; {:complete {:acc 15}}