From 2dd6432c6969b7ffe1c4a87d3d2a00e2f1025411 Mon Sep 17 00:00:00 2001
From: nathanmarz <nathan@nathanmarz.com>
Date: Sun, 7 May 2017 19:36:50 -0400
Subject: [PATCH] add set-elem navigator and change semantics of map-key to
 only navigate if the key exists (for consistency with set-elem)

---
 CHANGES.md                          |  1 +
 src/clj/com/rpl/specter.cljc        | 34 +++++++++++++++++++++++------
 test/com/rpl/specter/core_test.cljc |  8 ++++++-
 3 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/CHANGES.md b/CHANGES.md
index 3b702b1..dcc6306 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -2,6 +2,7 @@
 
 * Added `pred=`, `pred<`, `pred>`, `pred<=`, `pred>=` for filtering using common comparisons
 * Add `map-key` navigator
+* Add `set-elem` navigator
 
 ## 1.0.1
 
diff --git a/src/clj/com/rpl/specter.cljc b/src/clj/com/rpl/specter.cljc
index eb4d71e..499adc3 100644
--- a/src/clj/com/rpl/specter.cljc
+++ b/src/clj/com/rpl/specter.cljc
@@ -869,17 +869,37 @@
                             structure)))))
 
 (defrichnav
-  ^{:doc "Navigates to the given key in the map (not to the value). Navigates regardless
-          of whether the key currently exists in the map. For transforms, will assoc nil
-          value if key doesn't currently exist in map."}
+  ^{:doc "Navigates to the given key in the map (not to the value). Navigates only if the
+          key currently exists in the map."}
   map-key
   [key]
   (select* [this vals structure next-fn]
-    (next-fn vals key))
+    (if (contains? structure key)
+      (next-fn vals key)
+      NONE
+      ))
   (transform* [this vals structure next-fn]
-    (let [newkey (next-fn vals key)
-          oldval (get structure key)]
-      (-> structure (dissoc key) (assoc newkey oldval))
+    (if (contains? structure key)
+      (let [newkey (next-fn vals key)
+            oldval (get structure key)]
+        (-> structure (dissoc key) (assoc newkey oldval))
+        )
+      structure
+      )))
+
+(defrichnav
+  ^{:doc "Navigates to the given element in the set only if it exists in the set."}
+  set-elem
+  [elem]
+  (select* [this vals structure next-fn]
+    (if (contains? structure elem)
+      (next-fn vals elem)
+      NONE
+      ))
+  (transform* [this vals structure next-fn]
+    (if (contains? structure elem)
+      (-> structure (disj elem) (conj (next-fn vals elem)))
+      structure
       )))
 
 (def ^{:doc "Navigate to the specified keys one after another. If navigate to NONE,
diff --git a/test/com/rpl/specter/core_test.cljc b/test/com/rpl/specter/core_test.cljc
index 1f9f682..dcd9318 100644
--- a/test/com/rpl/specter/core_test.cljc
+++ b/test/com/rpl/specter/core_test.cljc
@@ -1528,11 +1528,17 @@
     ))
 
 (deftest map-key-test
-  (is (= {:b nil :c 3} (setval (s/map-key :a) :b {:c 3})))
+  (is (= {:c 3} (setval (s/map-key :a) :b {:c 3})))
   (is (= {:b 2} (setval (s/map-key :a) :b {:a 2})))
   (is (= {:b 2} (setval (s/map-key :a) :b {:a 2 :b 1})))
   )
 
+(deftest set-elem-test
+  (is (= #{:b :d} (setval (s/set-elem :a) :x #{:b :d})))
+  (is (= #{:x :a} (setval (s/set-elem :b) :x #{:b :a})))
+  (is (= #{:a} (setval (s/set-elem :b) :a #{:b :a})))
+  )
+
 #?(:clj
   (do
     (defprotocolpath FooPP)