feat(runtime-core): implement RFC-0020

BREAKING CHANGE: data no longer supports object format (per RFC-0020)

packages/runtime-core/__tests__/apiOptions.spec.ts

@@ -634,9 +634,9 @@ describe('api: options', () => {
     test('data property is already declared in props', () => {
       const Comp = {
         props: { foo: Number },
-        data: {
+        data: () => ({
           foo: 1
-        },
+        }),
         render() {}
       }
 
@@ -649,9 +649,9 @@ describe('api: options', () => {
 
     test('computed property is already declared in data', () => {
       const Comp = {
-        data: {
+        data: () => ({
           foo: 1
-        },
+        }),
         computed: {
           foo() {}
         },
@@ -699,9 +699,9 @@ describe('api: options', () => {
 
     test('methods property is already declared in data', () => {
       const Comp = {
-        data: {
+        data: () => ({
           foo: 2
-        },
+        }),
         methods: {
           foo() {}
         },