fix(step): fix steps doesn't work with v-for children (#1119)

Co-authored-by: 07akioni <07akioni2@gmail.com>

CHANGELOG.en-US.md

@@ -2,6 +2,10 @@
 
 ## Pending
 
+### Fixes
+
+- Fix `n-step` doesn't work with `v-for` children.
+
 ### Feats
 
 - `useDialog` option add `style` prop, closes [#1054](https://github.com/TuSimple/naive-ui/issues/1054).

CHANGELOG.zh-CN.md

@@ -2,6 +2,10 @@
 
 ## Pending
 
+### Fixes
+
+- 修复 `n-step` 无法使用 `v-for` 的子元素
+
 ### Feats
 
 - `useDialog` 选项新增 `style` 属性，关闭 [#1054](https://github.com/TuSimple/naive-ui/issues/1054)

src/steps/src/Steps.tsx

@@ -14,7 +14,7 @@ import type { MergedTheme, ThemeProps } from '../../_mixins'
 import { useConfig, useTheme } from '../../_mixins'
 import { stepsLight } from '../styles'
 import style from './styles/index.cssr'
-import { ExtractPublicPropTypes, getSlot } from '../../_utils'
+import { ExtractPublicPropTypes, flatten, getSlot } from '../../_utils'
 import type { StepsTheme } from '../styles'
 
 function stepWithIndex (step: VNodeChild, i: number): VNode | null {
@@ -87,7 +87,7 @@ export default defineComponent({
           this.vertical && `${mergedClsPrefix}-steps--vertical`
         ]}
       >
-        {stepsWithIndex(getSlot(this))}
+        {stepsWithIndex(flatten(getSlot(this)))}
       </div>
     )
   }