add multi-path implementation

src/clj/com/rpl/specter.clj

@@ -203,3 +203,9 @@
   ([cond-fn if-path] (cond-path cond-fn if-path))
   ([cond-fn if-path else-path]
     (cond-path cond-fn if-path nil else-path)))
+
+(defn multi-path
+  "A path that branches on multiple paths. For updates,
+   applies updates to the paths in order."
+  [& paths]
+  (->MultiPath (->> paths (map comp-paths*) doall)))

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

@@ -47,6 +47,7 @@
 (defprotocol CoerceTransformFunctions
   (coerce-path [this]))
 
+
 (defn no-prot-error-str [obj]
   (str "Protocol implementation cannot be found for object.
         Extending Specter protocols should not be done inline in a deftype definition
@@ -519,3 +520,21 @@
       structure
       )))
 
+(deftype MultiPath [paths])
+
+(extend-protocol StructurePath
+  MultiPath
+  (select* [this structure next-fn]
+    (->> (.paths this)
+         (mapcat #(compiled-select* % structure))
+         (mapcat next-fn)
+         doall
+         ))
+  (transform* [this structure next-fn]
+    (reduce
+      (fn [structure selector]
+        (compiled-transform* selector next-fn structure))
+      structure
+      (.paths this))
+    ))
+

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

@@ -345,3 +345,20 @@
        (= (select (if-path [k1 pred] k2 k3) m)
           (select k m)) 
        ))))
+
+(defspec multi-path-test
+  (for-all+
+    [k1 (max-size 3 gen/keyword)
+    k2 (max-size 3 gen/keyword)
+    m (max-size 5
+                (gen-map-with-keys
+                 gen/keyword
+                 gen/int
+                 k1
+                 k2))
+    ]
+    (= (transform (multi-path k1 k2) inc m)
+       (->> m
+            (transform k1 inc)
+            (transform k2 inc)))
+    ))