chore: update return types in form item lookup functions

Author: RylanBot

packages/components/form/utils/index.ts

@@ -1,19 +1,22 @@
 import { get, has, isArray, isEmpty, isObject } from 'lodash-es';
-import { FormItemInstance } from '../FormItem';
+import type { FormItemInstance } from '../FormItem';
 import type { NamePath } from '../type';
 
 /**
  * 在 `formMap` 中查找指定的 `FormItem`
  * (仅查找当前层级)
  */
-export function findFormItem(name: NamePath, formMapRef: React.MutableRefObject<Map<any, any>>) {
+export function findFormItem(
+  name: NamePath,
+  formMapRef: React.MutableRefObject<Map<any, any>>,
+): React.RefObject<FormItemInstance> | undefined {
   if (!formMapRef.current) return;
   // 提取所有 map key
   const mapKeys = [...formMapRef.current.keys()];
   // 转译为字符串后比对 key 兼容数组格式
   const key = mapKeys.find((key) => String(key) === String(name));
   // 拿到 key 引用地址获取 value
-  return formMapRef.current.get(key) as React.RefObject<FormItemInstance>;
+  return formMapRef.current.get(key);
 }
 
 /**
@@ -24,8 +27,8 @@ export function findFormItemDeep(
   name: NamePath,
   formMapRef: React.MutableRefObject<Map<any, any>>,
   depth = 0,
-): React.RefObject<FormItemInstance> | null {
-  if (!formMapRef?.current) return null;
+): React.RefObject<FormItemInstance> | undefined {
+  if (!formMapRef?.current) return;
   const targetPath = Array.isArray(name) ? name : [name];
   for (const [key, ref] of formMapRef.current.entries()) {
     const formItem = ref?.current;
@@ -38,7 +41,6 @@ export function findFormItemDeep(
     const found = findFormItemDeep(name, formListMapRef, depth + 1);
     if (found) return found;
   }
-  return null;
 }
 
 // { user: { name: '' } } => [['user', 'name']]