fix(components): [popper] prioritise user's popper-style (#12833)

* fix(components): [popper] prioritise users popper-style

fix: #12831

* test: fix packages/popper testcase

packages/components/popper/__tests__/content.test.tsx

@@ -75,14 +75,14 @@ describe('<ElPopperContent />', () => {
       expect(wrapper.classes()).toEqual(['el-popper', 'is-dark'])
       expect(wrapper.vm.contentStyle).toHaveLength(3)
       expect(wrapper.vm.contentStyle[0]).toHaveProperty('zIndex')
-      expect(wrapper.vm.contentStyle[1]).toEqual({})
-      expect(wrapper.vm.contentStyle[2]).toEqual(
+      expect(wrapper.vm.contentStyle[1]).toEqual(
         expect.objectContaining({
           position: 'absolute',
           top: '0',
           left: '0',
         })
       )
+      expect(wrapper.vm.contentStyle[2]).toEqual({})
     })
 
     it('should be able to be pure and themed', async () => {
@@ -108,7 +108,7 @@ describe('<ElPopperContent />', () => {
         popperStyle: style,
       })
 
-      expect(wrapper.vm.contentStyle[1]).toEqual(style)
+      expect(wrapper.vm.contentStyle[2]).toEqual(style)
     })
 
     it('should be able to emit events', async () => {

packages/components/popper/src/composables/use-content-dom.ts

@@ -29,8 +29,8 @@ export const usePopperContentDOM = (
   const contentStyle = computed<StyleValue[]>(() => {
     return [
       { zIndex: unref(contentZIndex) } as CSSProperties,
-      props.popperStyle || {},
       unref(styles).popper as CSSProperties,
+      props.popperStyle || {},
     ]
   })
   const ariaModal = computed<string | undefined>(() =>