fix(core): handle edge cases for functional component returning arrays

fix vuejs#7282

src/core/vdom/create-component.js

@@ -107,7 +107,7 @@ export function createComponent (
   context: Component,
   children: ?Array<VNode>,
   tag?: string
-): VNode | void {
+): VNode | Array<VNode> | void {
   if (isUndef(Ctor)) {
     return
   }

src/core/vdom/create-element.js

@@ -30,7 +30,7 @@ export function createElement (
   children: any,
   normalizationType: any,
   alwaysNormalize: boolean
-): VNode {
+): VNode | Array<VNode> {
   if (Array.isArray(data) || isPrimitive(data)) {
     normalizationType = children
     children = data
@@ -48,7 +48,7 @@ export function _createElement (
   data?: VNodeData,
   children?: any,
   normalizationType?: number
-): VNode {
+): VNode | Array<VNode> {
   if (isDef(data) && isDef((data: any).__ob__)) {
     process.env.NODE_ENV !== 'production' && warn(
       `Avoid using observed data object as vnode data: ${JSON.stringify(data)}\n` +
@@ -117,7 +117,9 @@ export function _createElement (
     vnode = createComponent(tag, data, context, children)
   }
   if (isDef(vnode)) {
-    if (ns) applyNS(vnode, ns)
+    if (ns && !Array.isArray(vnode)) {
+      applyNS(vnode, ns)
+    }
     return vnode
   } else {
     return createEmptyVNode()

src/core/vdom/create-functional-component.js

@@ -3,6 +3,7 @@
 import VNode from './vnode'
 import { createElement } from './create-element'
 import { resolveInject } from '../instance/inject'
+import { normalizeChildren } from '../vdom/helpers/normalize-children'
 import { resolveSlots } from '../instance/render-helpers/resolve-slots'
 import { installRenderHelpers } from '../instance/render-helpers/index'
 
@@ -47,8 +48,8 @@ function FunctionalRenderContext (
 
   if (options._scopeId) {
     this._c = (a, b, c, d) => {
-      const vnode: ?VNode = createElement(contextVm, a, b, c, d, needNormalization)
-      if (vnode) {
+      const vnode = createElement(contextVm, a, b, c, d, needNormalization)
+      if (vnode && !Array.isArray(vnode)) {
         vnode.fnScopeId = options._scopeId
         vnode.fnContext = parent
       }
@@ -67,7 +68,7 @@ export function createFunctionalComponent (
   data: VNodeData,
   contextVm: Component,
   children: ?Array<VNode>
-): VNode | void {
+): VNode | Array<VNode> | void {
   const options = Ctor.options
   const props = {}
   const propOptions = options.props
@@ -91,14 +92,23 @@ export function createFunctionalComponent (
   const vnode = options.render.call(null, renderContext._c, renderContext)
 
   if (vnode instanceof VNode) {
-    vnode.fnContext = contextVm
-    vnode.fnOptions = options
-    if (data.slot) {
-      (vnode.data || (vnode.data = {})).slot = data.slot
+    setFunctionalContextForVNode(vnode, data, contextVm, options)
+    return vnode
+  } else if (Array.isArray(vnode)) {
+    const vnodes = normalizeChildren(vnode) || []
+    for (let i = 0; i < vnodes.length; i++) {
+      setFunctionalContextForVNode(vnodes[i], data, contextVm, options)
     }
+    return vnodes
   }
+}
 
-  return vnode
+function setFunctionalContextForVNode (vnode, data, vm, options) {
+  vnode.fnContext = vm
+  vnode.fnOptions = options
+  if (data.slot) {
+    (vnode.data || (vnode.data = {})).slot = data.slot
+  }
 }
 
 function mergeProps (to, from) {

test/unit/features/options/functional.spec.js

@@ -186,6 +186,62 @@ describe('Options functional', () => {
     expect(vnode).toEqual(createEmptyVNode())
   })
 
+  // #7282
+  it('should normalize top-level arrays', () => {
+    const Foo = {
+      functional: true,
+      render (h) {
+        return [h('span', 'hi'), null]
+      }
+    }
+    const vm = new Vue({
+      template: `<div><foo/></div>`,
+      components: { Foo }
+    }).$mount()
+    expect(vm.$el.innerHTML).toBe('<span>hi</span>')
+  })
+
+  it('should work when used as named slot and returning array', () => {
+    const Foo = {
+      template: `<div><slot name="test"/></div>`
+    }
+
+    const Bar = {
+      functional: true,
+      render: h => ([
+        h('div', 'one'),
+        h('div', 'two'),
+        h(Baz)
+      ])
+    }
+
+    const Baz = {
+      functional: true,
+      render: h => h('div', 'three')
+    }
+
+    const vm = new Vue({
+      template: `<foo><bar slot="test"/></foo>`,
+      components: { Foo, Bar }
+    }).$mount()
+
+    expect(vm.$el.innerHTML).toBe('<div>one</div><div>two</div><div>three</div>')
+  })
+
+  it('should apply namespace when returning arrays', () => {
+    const Child = {
+      functional: true,
+      render: h => ([h('foo'), h('bar')])
+    }
+    const vm = new Vue({
+      template: `<svg><child/></svg>`,
+      components: { Child }
+    }).$mount()
+
+    expect(vm.$el.childNodes[0].namespaceURI).toContain('svg')
+    expect(vm.$el.childNodes[1].namespaceURI).toContain('svg')
+  })
+
   it('should work with render fns compiled from template', done => {
     // code generated via vue-template-es2015-compiler
     var render = function (_h, _vm) {