fix(utils): [vnode] flattedChildren support subTree

packages/components/tabs/__tests__/tabs.test.tsx

@@ -1,4 +1,4 @@
-import { nextTick, ref } from 'vue'
+import { defineComponent, nextTick, ref } from 'vue'
 import { mount } from '@vue/test-utils'
 import { describe, expect, test, vi } from 'vitest'
 import { EVENT_CODE } from '@element-plus/constants'
@@ -8,6 +8,17 @@ import TabNav from '../src/tab-nav'
 import type { TabPaneName } from '../src/tabs'
 import type { TabsPaneContext } from '@element-plus/tokens'
 
+const Comp = defineComponent({
+  components: {
+    TabPane,
+  },
+  template: `
+  <TabPane name="tab1" label="tab1">
+    Tab 1 content
+  </TabPane>
+    `,
+})
+
 describe('Tabs.vue', () => {
   test('create', async () => {
     const wrapper = mount(() => (
@@ -754,4 +765,17 @@ describe('Tabs.vue', () => {
     expect(navItemsWrapper[2].classes('is-active')).toBe(true)
     expect(navItemsWrapper[3].classes('is-active')).toBe(false)
   })
+
+  test('tab-pane nested', async () => {
+    const wrapper = mount(() => (
+      <Tabs>
+        <Comp />
+      </Tabs>
+    ))
+
+    const panesWrapper = wrapper.findAllComponents(TabPane)
+    await nextTick()
+
+    expect(panesWrapper.length).toBe(1)
+  })
 })

packages/utils/vue/vnode.ts

@@ -159,6 +159,9 @@ export const flattedChildren = (
       result.push(...flattedChildren(child.children))
     } else {
       result.push(child)
+      if (isVNode(child) && child.component && child.component.subTree) {
+        result.push(...flattedChildren(child.component.subTree.children))
+      }
     }
   })
   return result