fix: pass refs to functional component stubs

Fixes vuejs#1292

Author: xanf

Diff for: packages/create-instance/create-component-stubs.js

@@ -42,7 +42,6 @@ function getCoreProperties(componentOptions: Component): Object {
     props: componentOptions.props,
     on: componentOptions.on,
     key: componentOptions.key,
-    ref: componentOptions.ref,
     domProps: componentOptions.domProps,
     class: componentOptions.class,
     staticClass: componentOptions.staticClass,
@@ -96,6 +95,7 @@ export function createStubFromComponent(
       return h(
         tagName,
         {
+          // ref: componentOptions.functional ? context.data.ref : undefined,
           attrs: componentOptions.functional
             ? {
                 ...context.props,

Diff for: test/specs/mounting-options/stubs.spec.js

@@ -525,6 +525,30 @@ describeWithShallowAndMount('options.stub', mountingMethod => {
     expect(wrapper.html()).to.contain('h1')
   })
 
+  it('maintains refs to components', () => {
+    const FunctionalComponentPassingRef = {
+      functional: true,
+      render: (h, context) => h('div', context.data)
+    }
+
+    const TestComponent = {
+      template: `
+        <div>
+          <test-component ref="normalChild" />
+          <test-functional-component ref="functionalChild" />
+        </div>
+      `,
+      components: {
+        testComponent: Component,
+        testFunctionalComponent: FunctionalComponentPassingRef
+      }
+    }
+
+    const wrapper = mountingMethod(TestComponent)
+    expect(wrapper.vm.$refs.normalChild).to.exist
+    expect(wrapper.vm.$refs.functionalChild).to.exist
+  })
+
   it('uses original component stub', () => {
     const Stub = {
       template: '<div />'