rename _h -> _c so that vue-template-es2015-compiler can use the new internal createElement without breaking backwards compatibility

Author: yyx990803

flow/component.js

@@ -81,7 +81,7 @@ declare interface Component {
   _render: () => VNode;
   __patch__: (a: Element | VNode | void, b: VNode) => any;
   // createElement
-  _h: (vnode?: VNode, data?: VNodeData, children?: VNodeChildren) => VNode | void;
+  _c: (vnode?: VNode, data?: VNodeData, children?: VNodeChildren) => VNode | void;
   // renderStatic
   _m: (index: number, isInFor?: boolean) => VNode | VNodeChildren;
   // markOnce

src/compiler/codegen/index.js

@@ -31,7 +31,7 @@ export function generate (
   transforms = pluckModuleFunction(options.modules, 'transformCode')
   dataGenFns = pluckModuleFunction(options.modules, 'genData')
   platformDirectives = options.directives || {}
-  const code = ast ? genElement(ast) : '_h("div")'
+  const code = ast ? genElement(ast) : '_c("div")'
   staticRenderFns = prevStaticRenderFns
   onceCount = prevOnceCount
   return {
@@ -62,7 +62,7 @@ function genElement (el: ASTElement): string {
       const data = el.plain ? undefined : genData(el)
 
       const children = el.inlineTemplate ? null : genChildren(el, true)
-      code = `_h('${el.tag}'${
+      code = `_c('${el.tag}'${
         data ? `,${data}` : '' // data
       }${
         children ? `,${children}` : '' // children
@@ -336,7 +336,7 @@ function genSlot (el: ASTElement): string {
 // componentName is el.component, take it as argument to shun flow's pessimistic refinement
 function genComponent (componentName, el): string {
   const children = el.inlineTemplate ? null : genChildren(el, true)
-  return `_h(${componentName},${genData(el)}${
+  return `_c(${componentName},${genData(el)}${
     children ? `,${children}` : ''
   })`
 }

src/core/instance/render.js

@@ -32,9 +32,11 @@ export function initRender (vm: Component) {
   vm.$scopedSlots = {}
   // bind the createElement fn to this instance
   // so that we get proper render context inside it.
-  // args order: tag, data, children, needNormalization
-  // the needNormalization flag is disabled for the public version.
-  vm._h = (a, b, c, d) => createElement(vm, a, b, c, d, false)
+  // args order: tag, data, children, needNormalization, alwaysNormalize
+  // internal version is used by render functions compiled from templates
+  vm._c = (a, b, c, d) => createElement(vm, a, b, c, d, false)
+  // normalization is always applied for the public version, used in
+  // user-written render functions.
   vm.$createElement = (a, b, c, d) => createElement(vm, a, b, c, d, true)
   if (vm.$options.el) {
     vm.$mount(vm.$options.el)

test/unit/modules/compiler/compiler-options.spec.js

@@ -51,7 +51,7 @@ describe('compile options', () => {
             result[validator.name] = null
           })
           // generate code
-          return `_h('validate',{props:{
+          return `_c('validate',{props:{
             field:${JSON.stringify(el.validate.field)},
             groups:${JSON.stringify(el.validate.groups)},
             validators:${JSON.stringify(el.validators)},