empty selectors and nil count as identity path now fixing #5, remove IDENTITY-PATH in favor of nil

src/clj/com/rpl/specter.clj

@@ -124,8 +124,6 @@
 
 (def FIRST (->FirstStructurePath))
 
-(def IDENTITY-PATH (->IdentityPath))
-
 (defn srange-dynamic [start-fn end-fn] (->SRangePath start-fn end-fn))
 
 (defn srange [start end] (srange-dynamic (fn [_] start) (fn [_] end)))

src/clj/com/rpl/specter/impl.clj

@@ -121,6 +121,9 @@
   (or (fn? obj) (obj-extends? StructurePath obj)))
 
 (extend-protocol CoerceTransformFunctions
+  nil ; needs its own path because it doesn't count as an Object
+  (coerce-path [this]
+    (coerce-structure-path nil))
 
   TransformFunctions
   (coerce-path [this]
@@ -145,6 +148,8 @@
     ))
 
 (defn- combine-same-types [[^TransformFunctions f & _ :as all]]
+  (if (empty? all)
+    (coerce-path nil)
     (let [^ExecutorFunctions exs (.executors f)
 
           t (.type exs)
@@ -168,7 +173,7 @@
                  (combiner (.selector curr) (.selector next))
                  (combiner (.updater curr) (.updater next))
                  ))
-             all)))
+              all))))
 
 (defn coerce-structure-vals [^TransformFunctions tfns]
   (if (= (extype tfns) :svalspath)
@@ -448,16 +453,6 @@
     (->> structure ((.view-fn this)) next-fn)
     ))
 
-(deftype IdentityPath [])
-
-(extend-protocol StructurePath
-  IdentityPath
-  (select* [this structure next-fn]
-    (next-fn structure))
-  (update* [this structure next-fn]
-    (next-fn structure)
-    ))
-
 (deftype PutValCollector [val])
 
 (extend-protocol Collector
@@ -466,3 +461,11 @@
     (.val this)
     ))
 
+
+(extend-protocol StructurePath
+  nil
+  (select* [this structure next-fn]
+    (next-fn structure))
+  (update* [this structure next-fn]
+    (next-fn structure)
+    ))

test/clj/com/rpl/specter/core_test.clj

@@ -232,8 +232,8 @@
   (for-all+
     [i gen/int
      afn (gen/elements [inc dec])]
-    (and (= [i] (select IDENTITY-PATH i))
-         (= (afn i) (update IDENTITY-PATH afn i)))))
+    (and (= [i] (select nil i))
+         (= (afn i) (update nil afn i)))))
 
 (defspec putval-test
   (for-all+
@@ -245,3 +245,29 @@
       (assoc m kw (+ c (get m kw)))
       )))
 
+(defspec empty-selector-test
+  (for-all+
+   [v (gen/vector gen/int)]
+   (= [v]
+      (select [] v)
+      (select nil v)
+      (select (comp-paths) v)
+      (select (comp-paths nil) v)
+      (select [nil nil nil] v)
+      )))
+
+(defspec empty-selector-update-test
+  (for-all+
+   [kw gen/keyword
+    m (max-size 10 (gen-map-with-keys gen/keyword gen/int kw))]
+   (and (= m
+           (update nil identity m)
+           (update [] identity m)
+           (update (comp-paths []) identity m)
+           (update (comp-paths nil nil) identity m)
+           )
+        (= (update kw inc m)
+           (update [nil kw] inc m)
+           (update (comp-paths kw nil) inc m)
+           (update (comp-paths nil kw nil) inc m)
+           ))))