From 04f5146aa4a87f0eafc9b0059102e218757a511e Mon Sep 17 00:00:00 2001
From: homura <homura.dev@gmail.com>
Date: Wed, 13 Dec 2023 20:44:57 +0800
Subject: [PATCH] feat(codec): throw when duplicated ids are found

---
 packages/codec/src/molecule/layout.ts | 8 ++++++++
 packages/codec/tests/molecule.test.ts | 4 ++++
 2 files changed, 12 insertions(+)

diff --git a/packages/codec/src/molecule/layout.ts b/packages/codec/src/molecule/layout.ts
index 1d987ed79..b0490db56 100644
--- a/packages/codec/src/molecule/layout.ts
+++ b/packages/codec/src/molecule/layout.ts
@@ -338,6 +338,14 @@ export function union<T extends Record<string, BytesCodec>>(
 ): UnionCodec<T> {
   checkShape(itemCodec, Array.isArray(fields) ? fields : Object.keys(fields));
 
+  // check duplicated id
+  if (!Array.isArray(fields)) {
+    const ids = Object.values(fields);
+    if (ids.length !== new Set(ids).size) {
+      throw new Error(`Duplicated id in union: ${ids.join(", ")}`);
+    }
+  }
+
   return createBytesCodec({
     pack(obj) {
       const availableFields: (keyof T)[] = Object.keys(itemCodec);
diff --git a/packages/codec/tests/molecule.test.ts b/packages/codec/tests/molecule.test.ts
index f5fae16e9..aa9a0538f 100644
--- a/packages/codec/tests/molecule.test.ts
+++ b/packages/codec/tests/molecule.test.ts
@@ -229,6 +229,10 @@ test("test union with custom id", (t) => {
   ]));
 });
 
+test("test union with duplicated custom id", (t) => {
+  t.throws(() => union({ key1: Uint8, key2: Uint32LE }, { key1: 0, key2: 0 }));
+});
+
 test("test byteOf", (t) => {
   t.deepEqual(byteOf(Uint8).pack(1), bytify([1]));
   t.throws(() => byteOf(Uint16).pack(1));