fix(nerv-server): extend the method of renderVodeToString to support void and array vnode

packages/nerv-server/__tests__/render.spec.js

@@ -1,5 +1,5 @@
 /** @jsx createElement */
-import { Component, createElement } from 'nervjs'
+import { Component, createElement, Fragment } from 'nervjs'
 import sinon from 'sinon'
 import { renderToString } from '../src'
 const render = renderToString
@@ -92,6 +92,16 @@ describe('render', () => {
         `<svg><image xlink:href="#"></image><foreignObject><div xlinkHref="#"></div></foreignObject><g><image xlink:href="#"></image></g></svg>`
       )
     })
+
+    it('should render Fragment child elements', () => {
+      const rendered = render(
+        <Fragment>
+          {[1].map(() => <div>Fragment</div>)}
+        </Fragment>
+      )
+      const expected = `<div>Fragment</div>`
+      expect(rendered).toEqual(expected)
+    })
   })
 
   describe('Functional component', () => {

packages/nerv-server/src/index.ts

@@ -157,7 +157,14 @@ function renderVNodeToString (vnode, parent, context, isSvg?: boolean) {
       context = extend(clone(context), instance.getChildContext())
     }
     return renderVNodeToString(rendered, vnode, context, isSvg)
+  } else if (Array.isArray(vnode)) {
+    let result = ''
+    vnode.forEach((vnodeItem) => {
+      result += renderVNodeToString(vnodeItem, {}, {})
+    })
+    return result
   }
+  return ''
 }
 
 export function renderToString (input: any): string {