fix: add v-show style in ssr if style is binding to an array

web/server/directives/show just add style.display='none', no matter style is object or array; If
style is an array, it will lost additional property while tranformed into object in
shared/utils#toObject;

fix vuejs#7813

Author: lupengyu

src/platforms/web/server/directives/show.js

@@ -3,6 +3,10 @@
 export default function show (node: VNodeWithData, dir: VNodeDirective) {
   if (!dir.value) {
     const style: any = node.data.style || (node.data.style = {})
-    style.display = 'none'
+    if (Array.isArray(style)) {
+      style.push({ display: 'none' })
+    } else {
+      style.display = 'none'
+    }
   }
 }

test/ssr/ssr-string.spec.js

@@ -267,6 +267,17 @@ describe('SSR: renderToString', () => {
     })
   })
 
+  it('v-show directive merge with style', done => {
+    renderVmWithOptions({
+      template: '<div :style="[{lineHeight: 1}]" v-show="false"><span>inner</span></div>'
+    }, res => {
+      expect(res).toContain(
+        '<div data-server-rendered="true" style="line-height:1;display:none;"><span>inner</span></div>'
+      )
+      done()
+    })
+  })
+
   it('v-show directive not passed to child', done => {
     renderVmWithOptions({
       template: '<foo v-show="false"></foo>',