fix(runtime-dom): useCssVars work with static vnode

packages/runtime-dom/__tests__/helpers/useCssVars.spec.ts

@@ -2,6 +2,7 @@ import {
   ref,
   render,
   useCssVars,
+  createStaticVNode,
   h,
   reactive,
   nextTick,
@@ -140,4 +141,26 @@ describe('useCssVars', () => {
       expect((c as HTMLElement).style.getPropertyValue(`--color`)).toBe('red')
     }
   })
+
+  test('with createStaticVNode', async () => {
+    const state = reactive({ color: 'red' })
+    const root = document.createElement('div')
+
+    const App = {
+      setup() {
+        useCssVars(() => state)
+        return () => [
+          h('div'),
+          createStaticVNode('<div>1</div><div><span>2</span></div>', 2),
+          h('div')
+        ]
+      }
+    }
+
+    render(h(App), root)
+    await nextTick()
+    for (const c of [].slice.call(root.children as any)) {
+      expect((c as HTMLElement).style.getPropertyValue(`--color`)).toBe('red')
+    }
+  })
 })

packages/runtime-dom/src/helpers/useCssVars.ts

@@ -4,6 +4,7 @@ import {
   warn,
   VNode,
   Fragment,
+  Static,
   onUpdated,
   watchEffect
 } from '@vue/runtime-core'
@@ -53,5 +54,25 @@ function setVarsOnVNode(vnode: VNode, vars: Record<string, string>) {
     }
   } else if (vnode.type === Fragment) {
     ;(vnode.children as VNode[]).forEach(c => setVarsOnVNode(c, vars))
+  } else if (vnode.type === Static) {
+    const { el, anchor } = vnode
+    let current: HTMLElement | null = el as HTMLElement
+    while (current) {
+      setVarsOnElement(current, vars)
+      if (current === anchor) break
+      current = current.nextSibling as HTMLElement
+    }
+  }
+
+  function setVarsOnElement(el: HTMLElement, vars: Record<string, string>) {
+    const style = el.style
+    for (const key in vars) {
+      style.setProperty(`--${key}`, vars[key])
+    }
+
+    for (var i = 0; i < el.children.length; i++) {
+      const n = el.children[i]
+      setVarsOnElement(n as HTMLElement, vars)
+    }
   }
 }