feat(components): [table] export columns (#17252)

* feat(components): [el-table] export columns

* feat: add test and fix

docs/en-US/component/table.md

@@ -332,6 +332,8 @@ table/table-layout
 | scrollTo           | scrolls to a particular set of coordinates                                                                                                                        | ^[Function]`(options: number \| ScrollToOptions, yCoord?: number) => void` |
 | setScrollTop       | set vertical scroll position                                                                                                                                      | ^[Function]`(top?: number) => void`                                        |
 | setScrollLeft      | set horizontal scroll position                                                                                                                                    | ^[Function]`(left?: number) => void`                                       |
+| columns ^(2.7.6)   | Get table columns context.                                                                                                                                        | ^[array]`TableColumnCtx<T>[]`                                              |
+
 
 ## Table-column API
 

packages/components/table/__tests__/table.test.ts

@@ -1019,6 +1019,30 @@ describe('Table.vue', () => {
 
       wrapper.unmount()
     })
+
+    it('get table columns', async () => {
+      const wrapper = mount({
+        components: {
+          ElTable,
+          ElTableColumn,
+        },
+        template: `
+        <div>
+          <el-table ref="table" :data="testData" highlight-current-row>
+            <el-table-column prop="name" sortable />
+            <el-table-column prop="release" sortable />
+          </el-table>
+        </div>
+        `,
+        data() {
+          return { testData: getTestData() }
+        },
+      })
+      const vm = wrapper.vm
+      await doubleWait()
+      expect(vm.$refs.table.columns.length).toBe(2)
+      wrapper.unmount()
+    })
   })
 
   it('hover', async () => {

packages/components/table/src/table-header/utils-helper.ts

@@ -20,7 +20,7 @@ const getAllColumns = <T>(
   return result
 }
 
-const convertToRows = <T>(
+export const convertToRows = <T>(
   originColumns: TableColumnCtx<T>[]
 ): TableColumnCtx<T>[] => {
   let maxLevel = 1

packages/components/table/src/table.vue

@@ -177,6 +177,7 @@ import TableHeader from './table-header'
 import TableBody from './table-body'
 import TableFooter from './table-footer'
 import useUtils from './table/utils-helper'
+import { convertToRows } from './table-header/utils-helper'
 import useStyle from './table/style-helper'
 import useKeyRender from './table/key-render-helper'
 import defaultProps from './table/defaults'
@@ -294,12 +295,17 @@ export default defineComponent({
       return props.emptyText || t('el.table.emptyText')
     })
 
+    const columns = computed(() => {
+      return convertToRows(store.states.originColumns.value)[0]
+    })
+
     useKeyRender(table)
 
     return {
       ns,
       layout,
       store,
+      columns,
       handleHeaderFooterMousewheel,
       handleMouseLeave,
       tableId,