How to compare data structures in clojure and highlight differences

What I really searched for was difform. Using clojure.data/diff is nice but does not work well in a unit test where larger structures are compared. Here is an example where data/diff does not perform as well as difform in my opinion:

(defn example []
  (let [data [{:foo 1} {:value [{:bar 2}]}]]
    (diff data
          [{:value [{:bar 2}]}])

    (difform data
          [{:value [{:bar 2}]}])))

;; => diff output
;; => [[{:foo 1} {:value [{:bar 2}]}] [{:value [{:bar 2}]}] nil]

;; => difform output
   [{:
 - foo 1} {:
   value [{:bar 2}]}]
;; => nil

Take a look at clojure.data/diff: http://clojure.github.io/clojure/clojure.data-api.html#clojure.data/diff

Examples:

async-demo.core> (use 'clojure.data)
nil
async-demo.core> (diff {:a 2 :b 4} {:a 2})
({:b 4} nil {:a 2})
async-demo.core> (diff [1 2 3 4] [1 2 6 7])
[[nil nil 3 4] [nil nil 6 7] [1 2]]
async-demo.core> (diff #{"one" "two" "three"} #{"one" "fourty-four"})
[#{"two" "three"} #{"fourty-four"} #{"one"}]

Differ is a recent library that seems to do a nice job:

(def person-map {:name "Robin"
                 :age 25
                 :sex :male
                 :phone {:home 99999999
                         :work 12121212})

(def person-diff (differ/diff person-map {:name "Robin Heggelund Hansen"
                                          :age 26
                                          :phone {:home 99999999})

;; person-diff will now be [{:name "Robin Heggelund Hansen"
;;                           :age 26}
;;                          {:sex 0
;;                           :phone {:work 0}]

EDITED: fix Differ repo URL that change from gitlab to GitHub

You can also visually diff two data structures using the gui-diff library.

(gui-diff {:a 1} {:a 2}) will shell out to an OS-appropriate gui diffing program to diff the two, potentially very large, data structures.