From e31192fd31919eb029c87fd9177cb054ec11b9de Mon Sep 17 00:00:00 2001
From: Jim Berlage <james.berlage@gmail.com>
Date: Mon, 3 Dec 2018 16:10:19 -0600
Subject: [PATCH] Allows for an arbitrary number of props in merge-props

---
 src/reagent/core.cljs            |  8 +++++---
 src/reagent/impl/util.cljs       | 20 +++++++++++--------
 test/reagent/impl/util_test.cljs | 34 ++++++++++++++++++++++++++++++++
 test/reagenttest/runtests.cljs   |  1 +
 4 files changed, 52 insertions(+), 11 deletions(-)
 create mode 100644 test/reagent/impl/util_test.cljs

diff --git a/src/reagent/core.cljs b/src/reagent/core.cljs
index b465109..344bb3d 100644
--- a/src/reagent/core.cljs
+++ b/src/reagent/core.cljs
@@ -195,10 +195,12 @@
   (dom/dom-node this))
 
 (defn merge-props
-  "Utility function that merges two maps, handling :class and :style
+  "Utility function that merges some maps, handling :class and :style
   specially, like React's transferPropsTo."
-  [defaults props]
-  (util/merge-props defaults props))
+  ([] (util/merge-props))
+  ([defaults] (util/merge-props defaults))
+  ([defaults props] (util/merge-props defaults props))
+  ([defaults props & others] (apply util/merge-props (concat [defaults props] others))))
 
 (defn flush
   "Render dirty components immediately to the DOM.
diff --git a/src/reagent/impl/util.cljs b/src/reagent/impl/util.cljs
index 6fabd93..23a14a8 100644
--- a/src/reagent/impl/util.cljs
+++ b/src/reagent/impl/util.cljs
@@ -123,14 +123,18 @@
       p2
       (assoc p2 :style style))))
 
-(defn merge-props [p1 p2]
-  (if (nil? p1)
-    p2
-    (do
-      (assert (map? p1)
-              (str "Property must be a map, not " (pr-str p1)))
-      (merge-style p1 (merge-class p1 (merge p1 p2))))))
-
+(defn merge-props
+  ([] nil)
+  ([p] p)
+  ([p1 p2]
+   (if (nil? p1)
+     p2
+     (do
+       (assert (map? p1)
+               (str "Property must be a map, not " (pr-str p1)))
+       (merge p1 (merge-style p1 (merge-class p1 p2))))))
+  ([p1 p2 & ps]
+   (apply merge-props (cons (merge-props p1 p2) ps))))
 
 (def ^:dynamic *always-update* false)
 
diff --git a/test/reagent/impl/util_test.cljs b/test/reagent/impl/util_test.cljs
new file mode 100644
index 0000000..81dfdea
--- /dev/null
+++ b/test/reagent/impl/util_test.cljs
@@ -0,0 +1,34 @@
+(ns reagent.impl.util-test
+  (:require [clojure.test :refer [deftest is testing]]
+            [reagent.impl.util :as util]))
+
+(deftest merge-props-test
+  (testing "It handles no arguments"
+    (is (nil? (util/merge-props))))
+  (testing "It handles one argument"
+    (is (nil? (util/merge-props nil)))
+    (is (= {:foo :bar} (util/merge-props {:foo :bar}))))
+  (testing "It handles two arguments"
+    (is (= {:disabled false :style {:flex 1 :flex-direction "row"} :class "foo bar"}
+           (util/merge-props {:disabled true :style {:flex 1} :class "foo"}
+                             {:disabled false :style {:flex-direction "row"} :class "bar"}))))
+  (testing "It handles n arguments"
+    (is (= {:disabled false
+            :checked true
+            :style {:align-items "flex-end"
+                    :justify-content "center"}
+            :class "foo bar baz quux"}
+           (util/merge-props {:disabled false
+                              :checked false
+                              :style {:align-items "flex-end"}
+                              :class "foo"}
+                             {:disabled false
+                              :checked false
+                              :class "bar"}
+                             {:disabled true
+                              :style {:justify-content "center"}
+                              :class "baz"}
+                             {:disabled false
+                              :checked true
+                              :class "quux"}
+                             nil)))))
diff --git a/test/reagenttest/runtests.cljs b/test/reagenttest/runtests.cljs
index b32d68a..24c108f 100644
--- a/test/reagenttest/runtests.cljs
+++ b/test/reagenttest/runtests.cljs
@@ -8,6 +8,7 @@
             [reagenttest.testwithlet]
             [reagenttest.testwrap]
             [reagent.impl.template-test]
+            [reagent.impl.util-test]
             [cljs.test :as test]
             [doo.runner :as doo :include-macros true]
             [reagent.core :as r]