add remove-unchanged API

Author: humorless

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Added
 
 - Enable print tests in babashka
+- Add namespace `lambdaisland.deep-diff2.strip` ns with `remove-unchanged` API
 
 ## Fixed
 

src/lambdaisland/deep_diff2/strip.cljc

@@ -0,0 +1,43 @@
+(ns lambdaisland.deep-diff2.strip
+  "Provide API for manipulate the diff structure data "
+  (:require [clojure.walk :refer [postwalk]]
+            #?(:clj [lambdaisland.deep-diff2.diff-impl]
+               :cljs [lambdaisland.deep-diff2.diff-impl :refer [Mismatch Deletion Insertion]]))
+  #?(:clj (: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)))
+
+(defn extend-flatten
+  "Flatten, which can apply on hashmap"
+  [x]
+  (filter (complement coll?)
+          (rest (tree-seq coll? seq x))))
+
+(defn has-diff-item?
+  "Checks if there are any diff items in x or sub-tree of x"
+  [x]
+  (some
+   #(or (= :- %) (= :+ %))
+   (extend-flatten x)))
+
+(defn remove-unchanged
+  "Postwalk diff, removing values that are unchanged"
+  [diff]
+  (postwalk
+   (fn [x]
+     (cond
+       (map-entry? x) (cond
+                        (diff-item? (key x)) (do
+                                               ;(println "cond 1, keep" x)
+                                               x)
+                        (has-diff-item? (val x)) (do
+                                                    ;(println "cond 2, keep" x)
+                                                   x))
+       :else          x))
+   diff))
+

test/lambdaisland/deep_diff2/strip_test.cljc

@@ -0,0 +1,23 @@
+(ns lambdaisland.deep-diff2.strip-test
+  (:require [clojure.test :refer [deftest testing is are]]
+            [lambdaisland.deep-diff2.diff-impl :as diff]
+            [lambdaisland.deep-diff2.strip :as strip]
+            [lambdaisland.deep-diff2 :as ddiff]))
+
+(deftest strip-test
+  (testing "removing the same items"
+    (let [x {:a 1 :b 2 :d {:e 1} :g [:e [:k 14 :g 15]]}
+          y {:a 1 :c 3 :d {:e 15} :g [:e [:k 14 :g 15]]}]
+      (is (= (ddiff/diff x y)
+             {:a 1
+              (diff/->Deletion :b) 2
+              :d {:e (diff/->Mismatch 1 15)}
+              :g [:e [:k 14 :g 15]]
+              (diff/->Insertion :c) 3}))))
+  (testing "removing the same items"
+    (let [x {:a 1 :b 2 :d {:e 1} :g [:e [:k 14 :g 15]]}
+          y {:a 1 :c 3 :d {:e 15} :g [:e [:k 14 :g 15]]}]
+      (is (= (strip/remove-unchanged (ddiff/diff x y))
+             {(diff/->Deletion :b) 2
+              :d {:e (diff/->Mismatch 1 15)}
+              (diff/->Insertion :c) 3})))))