From 4bcf345d7c757bb34ccd6c0cbdec9428f9d83985 Mon Sep 17 00:00:00 2001
From: Nikita Prokopov <niki@tonsky.me>
Date: Mon, 21 Oct 2024 14:31:59 +0200
Subject: [PATCH] Fixes read-handlers with multiple arities (closes #49)

---
 src/cognitect/transit.cljs  | 32 +++++++++++++++++---------------
 test/transit/test/core.cljs | 30 ++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 15 deletions(-)

diff --git a/src/cognitect/transit.cljs b/src/cognitect/transit.cljs
index 6ba787a..fb86ec2 100644
--- a/src/cognitect/transit.cljs
+++ b/src/cognitect/transit.cljs
@@ -115,21 +115,23 @@
      (t/reader (name type)
        (opts-merge
          #js {:handlers
-              (clj->js
-                (merge
-                  {"$"    (fn [v] (symbol v))
-                   ":"    (fn [v] (keyword v))
-                   "set"  (fn [v] (into #{} v))
-                   "list" (fn [v] (into () (.reverse v)))
-                   "cmap" (fn [v]
-                            (loop [i 0 ret (transient {})]
-                              (if (< i (alength v))
-                                (recur (+ i 2)
-                                  (assoc! ret (aget v i) (aget v (inc i))))
-                                (persistent! ret))))
-                   "with-meta"
-                          (fn [v] (with-meta (aget v 0) (aget v 1)))}
-                  (dissoc (:handlers opts) :default)))
+              (reduce-kv
+                (fn [m tag handler]
+                  (gobj/set m (clj->js tag) #(handler %))
+                  m)
+                #js {"$"    (fn [v] (symbol v))
+                     ":"    (fn [v] (keyword v))
+                     "set"  (fn [v] (into #{} v))
+                     "list" (fn [v] (into () (.reverse v)))
+                     "cmap" (fn [v]
+                              (loop [i 0 ret (transient {})]
+                                (if (< i (alength v))
+                                  (recur (+ i 2)
+                                    (assoc! ret (aget v i) (aget v (inc i))))
+                                  (persistent! ret))))
+                     "with-meta"
+                            (fn [v] (with-meta (aget v 0) (aget v 1)))}
+                (dissoc (:handlers opts) :default))
               :defaultHandler (-> opts :handlers :default)
               :mapBuilder (MapBuilder.)
               :arrayBuilder (VectorBuilder.)
diff --git a/test/transit/test/core.cljs b/test/transit/test/core.cljs
index dc7ce5c..6cce15e 100644
--- a/test/transit/test/core.cljs
+++ b/test/transit/test/core.cljs
@@ -131,6 +131,36 @@
   (is (= (t/read cr "[\"~:foo\", 1]")
          [:foo 1])))
 
+(deftest test-read-custom-arities
+  (is (= (t/read (t/reader :json
+                   {:handlers
+                    {"custom" (fn [x]
+                                x)}})
+           "[\"~#custom\",\"abc\"]")
+        "abc"))
+  (is (= (t/read (t/reader :json 
+                   {:handlers
+                    {"custom" (fn
+                                ([] nil)
+                                ([x] x))}})
+           "[\"~#custom\",\"abc\"]")
+        "abc"))
+  (is (= (t/read (t/reader :json 
+                   {:handlers
+                    {"custom" (fn
+                                ([x] x)
+                                ([x y] [x y]))}})
+           "[\"~#custom\",\"abc\"]")
+        "abc"))
+  (is (= (t/read (t/reader :json 
+                   {:handlers
+                    {"custom" (fn
+                                ([] nil)
+                                ([x] x)
+                                ([x y] [x y]))}})
+           "[\"~#custom\",\"abc\"]")
+        "abc")))
+
 (def cw
   (t/writer :json
     {:handlers