Strip unchanged values from a deep-diff2 report

diff-util.clj

;; solution attempt for https://github.com/lambdaisland/deep-diff2/issues/13

(require '[clojure.walk :refer [postwalk]]
         lambdaisland.deep-diff2.diff-impl
         '[lambdaisland.deep-diff2 :as ddiff])
(import '[lambdaisland.deep_diff2.diff_impl Mismatch Deletion Insertion])

(defn diff-item?
  "Checks if x is a Mismatch, Deletion, or Insertion"
  [x]
  (or (instance? Mismatch x)
      (instance? Deletion x)
      (instance? Insertion x)))

(def diff-or-col? #(or (coll? %) (diff-item? %)))

(defn remove-unchanged
  "Postwalk diff, removing values that are unchanged"
  [diff]
  (postwalk
    (fn [x]
      (cond
        (map-entry? x) (when (diff-or-coll? (val x)) x)
        (map? x)       (not-empty x)
        (coll? x)      (not-empty (into (empty x) (filter diff-or-coll?) x))
        :else          x))
    diff))

;; example usage
(ddiff/pretty-print (remove-unchanged (ddiff/diff a b)))