redplanetlabs#235 - submap sub map should maintain properties of pa…

…rent map

WORK IN PROGRESS

TODO: check if additional map types need support, implement and test submap! nav

Adding new SubMap protocol to handle the different implementations of key selection (including one that maintains order to be used for sorted-map)

Adding test to ensure order preserved for a large map

src/clj/com/rpl/specter.cljc

@@ -905,10 +905,10 @@
   submap
   [m-keys]
   (select* [this structure next-fn]
-    (next-fn (select-keys structure m-keys)))
+    (next-fn (n/get-submap structure m-keys)))
 
   (transform* [this structure next-fn]
-    (let [submap (select-keys structure m-keys)
+    (let [submap (n/get-submap structure m-keys)
           newmap (next-fn submap)]
       (merge (reduce dissoc structure m-keys)
              newmap))))

src/clj/com/rpl/specter/navs.cljc

@@ -691,3 +691,32 @@
     ((:end-fn end-fn) structure start)
     (end-fn structure)
     ))
+
+(defn- maintain-sorted-submap [structure m-keys]
+  (let [ordered-select-keys (fn [map keyseq]
+                                (let [s (set keyseq)]
+                                  (into (empty map) (select-keys map s))))]
+    (ordered-select-keys structure m-keys)))
+
+(defprotocol SubMap
+  (get-submap [structure m-keys]))
+
+(extend-protocol SubMap
+  nil
+  (get-submap [structure m-keys] nil)
+
+  #?(:clj clojure.lang.PersistentArrayMap :cljs cljs.core/PersistentArrayMap)
+  #?(:clj
+     (get-submap [structure m-keys]
+       (maintain-sorted-submap structure m-keys)))
+
+  #?(:clj clojure.lang.PersistentHashMap :cljs cljs.core/PersistentHashMap)
+  #?(:clj
+     (get-submap [structure m-keys]
+       (select-keys structure m-keys)))
+
+  #?(:clj clojure.lang.PersistentTreeMap :cljs cljs.core/PersistentTreeMap)
+  #?(:clj
+     (get-submap [structure m-keys]
+       (maintain-sorted-submap structure m-keys)))
+  )

src/clj/com/rpl/specter/protocols.cljc

@@ -25,3 +25,4 @@
 
 (defprotocol ImplicitNav
   (implicit-nav [obj]))
+

test/com/rpl/specter/core_test.cljc

@@ -623,7 +623,11 @@
   (is (= {:a {:new 1}
           :c {:new 1
               :old 1}}
-         (setval [s/ALL s/LAST (s/submap [])] {:new 1} {:a nil, :c {:old 1}}))))
+         (setval [s/ALL s/LAST (s/submap [])] {:new 1} {:a nil, :c {:old 1}})))
+  (let [range50 (range 50)]
+    (is (= (take-nth 2 range50)
+           (select [(s/submap (take-nth 2 range50)) s/MAP-KEYS] (apply sorted-map (interleave range50 range50))))))
+  )
 
 (deftest nil->val-test
   (is (= {:a #{:b}}