From 29a988445e8cee36a96c09bb72dba1480422f980 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=99=B3=E5=BB=B7=E5=AE=89?=
 <73953029+nrps9909@users.noreply.github.com>
Date: Thu, 27 Aug 2026 02:53:20 +0800
Subject: [PATCH] fix: preserve source when removing nested values

---
 src/utils/set.ts    |  5 ++++-
 tests/utils.test.ts | 12 +++++-------
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/utils/set.ts b/src/utils/set.ts
index 7d465a56..5d4cb3f5 100644
--- a/src/utils/set.ts
+++ b/src/utils/set.ts
@@ -25,7 +25,10 @@ function internalSet<Entity = any, Output = Entity, Value = any>(
 
   // Delete prop if `removeIfUndefined` and value is undefined
   if (removeIfUndefined && value === undefined && restPath.length === 1) {
-    delete clone[path][restPath[0]];
+    const origin = clone[path];
+    const child = Array.isArray(origin) ? [...origin] : { ...origin };
+    delete child[restPath[0]];
+    clone[path] = child;
   } else {
     clone[path] = internalSet(clone[path], restPath, value, removeIfUndefined);
   }
diff --git a/tests/utils.test.ts b/tests/utils.test.ts
index 842c172d..195e1c1f 100644
--- a/tests/utils.test.ts
+++ b/tests/utils.test.ts
@@ -59,14 +59,12 @@ describe('utils', () => {
       expect(set({}, ['notExist'], undefined, true)).toEqual({});
 
       // Delete value
-      const target = set(
-        { keep: { light: 2333 } },
-        ['keep', 'light'],
-        undefined,
-        true,
-      );
-      expect(target).toEqual({ keep: {} });
+      const source = { keep: { light: 2333, bamboo: 1 } };
+      const target = set(source, ['keep', 'light'], undefined, true);
+      expect(target).toEqual({ keep: { bamboo: 1 } });
       expect('light' in target.keep).toBeFalsy();
+      expect(source).toEqual({ keep: { light: 2333, bamboo: 1 } });
+      expect(target.keep).not.toBe(source.keep);
 
       // Mid path not exist
       const midTgt = set(