From e03a8060214d122ea2ebadf9e8a368f7f593d9f4 Mon Sep 17 00:00:00 2001
From: Philip Aston <philipa@mail.com>
Date: Sun, 10 Jun 2012 13:11:36 +0100
Subject: [PATCH] clojure.data/diff: cope with falsey values in maps

---
 src/clj/clojure/data.clj           |   18 +++++++++++++++++-
 test/clojure/test_clojure/data.clj |    3 ++-
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/clj/clojure/data.clj b/src/clj/clojure/data.clj
index 6e8dbcf..345b234 100644
--- a/src/clj/clojure/data.clj
+++ b/src/clj/clojure/data.clj
@@ -30,6 +30,22 @@
      (vec (repeat (apply max (keys m))  nil))
      m)))
 
+(defn- diff-associative-key
+  "Diff associative things a and b, comparing only the key k."
+  [a b k]
+  (let [va (get a k)
+        vb (get b k)
+        [a* b* ab] (diff va vb)
+        in-a (contains? a k)
+        in-b (contains? b k)
+        same (and in-a in-b
+                  (or (not (nil? ab))
+                      (and (nil? va) (nil? vb))))]
+    [(when (and in-a (or (not (nil? a*)) (not same))) {k a*})
+     (when (and in-b (or (not (nil? b*)) (not same))) {k b*})
+     (when same {k ab})
+     ]))
+
 (defn- diff-associative
   "Diff associative things a and b, comparing only keys in ks."
   [a b ks]
@@ -38,7 +54,7 @@
      (doall (map merge diff1 diff2)))
    [nil nil nil]
    (map
-    (fn [k] (map #(when % {k %}) (diff (get a k) (get b k))))
+    (partial diff-associative-key a b)
     ks)))
 
 (defn- diff-sequential
diff --git a/test/clojure/test_clojure/data.clj b/test/clojure/test_clojure/data.clj
index 9bab766..5a241e0 100644
--- a/test/clojure/test_clojure/data.clj
+++ b/test/clojure/test_clojure/data.clj
@@ -27,5 +27,6 @@
        [#{1} #{3} #{2}] (HashSet. [1 2]) (HashSet. [2 3])
        [nil nil [1 2]] [1 2] (into-array [1 2])
        [nil nil [1 2]] (into-array [1 2]) [1 2]
-       [{:a {:c [1]}} {:a {:c [0]}} {:a {:c [nil 2] :b 1}}] {:a {:b 1 :c [1 2]}} {:a {:b 1 :c [0 2]}}))
+       [{:a {:c [1]}} {:a {:c [0]}} {:a {:c [nil 2] :b 1}}] {:a {:b 1 :c [1 2]}} {:a {:b 1 :c [0 2]}}
+       [{:a nil} {:a false} {:b nil :c false}] {:a nil :b nil :c false} {:a false :b nil :c false}))
 
-- 
1.7.9.5