refactor: cache v-once and purely static trees separately

src/compiler/codegen/index.js

@@ -86,10 +86,16 @@ export function genElement (el: ASTElement, state: CodegenState): string {
 }
 
 // hoist static sub-trees out
-function genStatic (el: ASTElement, state: CodegenState): string {
+function genStatic (el: ASTElement, state: CodegenState, once: ?boolean): string {
   el.staticProcessed = true
   state.staticRenderFns.push(`with(this){return ${genElement(el, state)}}`)
-  return `_m(${state.staticRenderFns.length - 1}${el.staticInFor ? ',true' : ''})`
+  return `_m(${
+    state.staticRenderFns.length - 1
+  },${
+    el.staticInFor ? 'true' : 'false'
+  },${
+    once ? 'true' : 'false'
+  })`
 }
 
 // v-once
@@ -115,7 +121,7 @@ function genOnce (el: ASTElement, state: CodegenState): string {
     }
     return `_o(${genElement(el, state)},${state.onceId++},${key})`
   } else {
-    return genStatic(el, state)
+    return genStatic(el, state, true)
   }
 }
 

src/core/instance/render-helpers/render-static.js

@@ -7,12 +7,19 @@ import { cloneVNode, cloneVNodes } from 'core/vdom/vnode'
  */
 export function renderStatic (
   index: number,
-  isInFor?: boolean
+  isInFor: boolean,
+  isOnce: boolean
 ): VNode | Array<VNode> {
-  // static trees can be rendered once and cached on the contructor options
-  // so every instance shares the same cached trees
-  const options = this.$options
-  const cached = options.cached || (options.cached = [])
+  // render fns generated by compiler < 2.5.4 does not provide v-once
+  // information to runtime so be conservative
+  const isOldVersion = arguments.length < 3
+  // if a static tree is generated by v-once, it is cached on the instance;
+  // otherwise it is purely static and can be cached on the shared options
+  // across all instances.
+  const renderFns = this.$options.staticRenderFns
+  const cached = isOldVersion || isOnce
+    ? (this._staticTrees || (this._staticTrees = []))
+    : (renderFns.cached || (renderFns.cached = []))
   let tree = cached[index]
   // if has already-rendered static tree and not inside v-for,
   // we can reuse the same tree by doing a shallow clone.
@@ -22,7 +29,7 @@ export function renderStatic (
       : cloneVNode(tree)
   }
   // otherwise, render a fresh tree.
-  tree = cached[index] = options.staticRenderFns[index].call(this._renderProxy, null, this)
+  tree = cached[index] = renderFns[index].call(this._renderProxy, null, this)
   markStatic(tree, `__static__${index}`, false)
   return tree
 }

test/unit/modules/compiler/codegen.spec.js

@@ -478,7 +478,7 @@ describe('codegen', () => {
     // have "inline-template'"
     assertCodegen(
       '<my-component inline-template><p><span>hello world</span></p></my-component>',
-      `with(this){return _c('my-component',{inlineTemplate:{render:function(){with(this){return _m(0)}},staticRenderFns:[function(){with(this){return _c('p',[_c('span',[_v("hello world")])])}}]}})}`
+      `with(this){return _c('my-component',{inlineTemplate:{render:function(){with(this){return _m(0,false,false)}},staticRenderFns:[function(){with(this){return _c('p',[_c('span',[_v("hello world")])])}}]}})}`
     )
     // "have inline-template attrs, but not having exactly one child element
     assertCodegen(
@@ -498,7 +498,7 @@ describe('codegen', () => {
   it('generate static trees inside v-for', () => {
     assertCodegen(
       `<div><div v-for="i in 10"><p><span></span></p></div></div>`,
-      `with(this){return _c('div',_l((10),function(i){return _c('div',[_m(0,true)])}))}`,
+      `with(this){return _c('div',_l((10),function(i){return _c('div',[_m(0,true,false)])}))}`,
       [`with(this){return _c('p',[_c('span')])}`]
     )
   })