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index.js
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/* @flow */
import { decode } from 'he'
import { parseHTML } from './html-parser'
import { parseText } from './text-parser'
import { parseFilters } from './filter-parser'
import { cached, no, camelize } from 'shared/util'
import { genAssignmentCode } from '../directives/model'
import { isIE, isEdge, isServerRendering } from 'core/util/env'
import {
addProp,
addAttr,
baseWarn,
addHandler,
addDirective,
getBindingAttr,
getAndRemoveAttr,
pluckModuleFunction
} from '../helpers'
/*匹配@以及v-on,绑定事件 */
export const onRE = /^@|^v-on:/
/*匹配v-、@以及:*/
export const dirRE = /^v-|^@|^:/
/*匹配v-for中的in以及of*/
export const forAliasRE = /(.*?)\s+(?:in|of)\s+(.*)/
/*v-for参数中带括号的情况匹配,比如(item, index)这样的参数*/
export const forIteratorRE = /\((\{[^}]*\}|[^,]*),([^,]*)(?:,([^,]*))?\)/
/*Github:https://github.com/answershuto*/
const argRE = /:(.*)$/
/*匹配v-bind以及:*/
const bindRE = /^:|^v-bind:/
/*根据点来分开各个级别的正则,比如a.b.c.d解析后可以得到.b .c .d*/
const modifierRE = /\.[^.]+/g
const decodeHTMLCached = cached(decode)
// configurable state
export let warn
let delimiters
let transforms
let preTransforms
let postTransforms
let platformIsPreTag
let platformMustUseProp
let platformGetTagNamespace
/**
* Convert HTML string to AST.
*/
/*将HTML字符串转换成AST*/
export function parse (
template: string,
options: CompilerOptions
): ASTElement | void {
/*警告函数,baseWarn是Vue 编译器默认警告*/
warn = options.warn || baseWarn
platformGetTagNamespace = options.platformGetTagNamespace || no
platformMustUseProp = options.mustUseProp || no
/*检测是否是<pre>标签*/
platformIsPreTag = options.isPreTag || no
preTransforms = pluckModuleFunction(options.modules, 'preTransformNode')
transforms = pluckModuleFunction(options.modules, 'transformNode')
postTransforms = pluckModuleFunction(options.modules, 'postTransformNode')
delimiters = options.delimiters
/*存放ele*/
const stack = []
const preserveWhitespace = options.preserveWhitespace !== false
let root
let currentParent
/*标志位,是否有v-pre属性*/
let inVPre = false
/*标志位,是否是pre标签*/
let inPre = false
let warned = false
/*只发出一次的warning*/
function warnOnce (msg) {
if (!warned) {
warned = true
warn(msg)
}
}
function endPre (element) {
// check pre state
/*是否有v-pre属性,存在则标志位变为false,因为这里已经是结束end,存在v-pre时在start中会被标志为true*/
if (element.pre) {
inVPre = false
}
/*检测是否是<pre>标签*/
if (platformIsPreTag(element.tag)) {
inPre = false
}
}
/*解析HTML*/
parseHTML(template, {
warn,
expectHTML: options.expectHTML,
isUnaryTag: options.isUnaryTag,
canBeLeftOpenTag: options.canBeLeftOpenTag,
shouldDecodeNewlines: options.shouldDecodeNewlines,
start (tag, attrs, unary) {
// check namespace.
// inherit parent ns if there is one
const ns = (currentParent && currentParent.ns) || platformGetTagNamespace(tag)
// handle IE svg bug
/* istanbul ignore if */
/*处理IE的svg bug*/
if (isIE && ns === 'svg') {
attrs = guardIESVGBug(attrs)
}
const element: ASTElement = {
type: 1,
tag,
attrsList: attrs,
attrsMap: makeAttrsMap(attrs),
parent: currentParent,
children: []
}
if (ns) {
element.ns = ns
}
/*如果是被禁止的标签或者是服务端渲染*/
if (isForbiddenTag(element) && !isServerRendering()) {
element.forbidden = true
process.env.NODE_ENV !== 'production' && warn(
'Templates should only be responsible for mapping the state to the ' +
'UI. Avoid placing tags with side-effects in your templates, such as ' +
`<${tag}>` + ', as they will not be parsed.'
)
}
// apply pre-transforms
for (let i = 0; i < preTransforms.length; i++) {
preTransforms[i](element, options)
}
if (!inVPre) {
/*
处理v-pre属性
v-pre元素及其子元素被跳过编译
https://cn.vuejs.org/v2/api/#v-pre
*/
processPre(element)
if (element.pre) {
inVPre = true
}
}
/*检测是否是<pre>标签*/
if (platformIsPreTag(element.tag)) {
inPre = true
}
/*如果有v-pre属性,元素及其子元素不会被编译*/
if (inVPre) {
processRawAttrs(element)
} else {
/*匹配v-for属性*/
processFor(element)
/*匹配if属性,分别处理v-if、v-else以及v-else-if属性*/
processIf(element)
/*处理v-once属性,https://cn.vuejs.org/v2/api/#v-once*/
processOnce(element)
/*处理key属性 https://cn.vuejs.org/v2/api/#key*/
processKey(element)
// determine whether this is a plain element after
// removing structural attributes
/*去掉属性后,确定这是一个普通元素。*/
element.plain = !element.key && !attrs.length
/*处理ref属性 https://cn.vuejs.org/v2/api/#ref*/
processRef(element)
/*处理slot属性 https://cn.vuejs.org/v2/api/#slot*/
processSlot(element)
/*处理组件*/
processComponent(element)
/*转换*/
for (let i = 0; i < transforms.length; i++) {
transforms[i](element, options)
}
/*处理属性*/
processAttrs(element)
}
/*监测根级元素的约束*/
function checkRootConstraints (el) {
if (process.env.NODE_ENV !== 'production') {
/*slot以及templete不能作为根级元素*/
if (el.tag === 'slot' || el.tag === 'template') {
warnOnce(
`Cannot use <${el.tag}> as component root element because it may ` +
'contain multiple nodes.'
)
}
/*以及根级元素不能有v-for*/
if (el.attrsMap.hasOwnProperty('v-for')) {
warnOnce(
'Cannot use v-for on stateful component root element because ' +
'it renders multiple elements.'
)
}
}
}
// tree management
if (!root) {
root = element
/*检测根级元素的约束*/
checkRootConstraints(root)
} else if (!stack.length) {
// allow root elements with v-if, v-else-if and v-else
/*
根级元素是可以用v-if、v-else来写多个条件下的多个根级元素的
比如说
<template>
<div v-if="fff">aaa</div>
<div v-else>bbb</div>
</template>
是完全允许的
*/
if (root.if && (element.elseif || element.else)) {
/*监测根级元素的约束*/
checkRootConstraints(element)
/*在el的ifConditions属性中加入condition*/
addIfCondition(root, {
exp: element.elseif,
block: element
})
} else if (process.env.NODE_ENV !== 'production') {
/*在根级元素包含多个ele的时候,有不含v-else的ele则报出打印*/
warnOnce(
`Component template should contain exactly one root element. ` +
`If you are using v-if on multiple elements, ` +
`use v-else-if to chain them instead.`
)
}
}
/*forbidden标志是否是被禁止的标签(style标签或者script标签)*/
if (currentParent && !element.forbidden) {
if (element.elseif || element.else) {
/*当遇到当前ele有v-else或者v-elseif属性的时候,需要处理if属性,在其上级兄弟元素中必然存在一个v-if属性*/
processIfConditions(element, currentParent)
} else if (element.slotScope) { // scoped slot
currentParent.plain = false
/*slot如果没有则是默认的default*/
const name = element.slotTarget || '"default"'
/*
scopedSlots中存放slot元素 https://cn.vuejs.org/v2/api/#vm-scopedSlots
*/
;(currentParent.scopedSlots || (currentParent.scopedSlots = {}))[name] = element
} else {
currentParent.children.push(element)
element.parent = currentParent
}
}
if (!unary) {
currentParent = element
stack.push(element)
} else {
endPre(element)
}
// apply post-transforms
for (let i = 0; i < postTransforms.length; i++) {
postTransforms[i](element, options)
}
},
end () {
// remove trailing whitespace
/*从stack中取出最后一个ele*/
const element = stack[stack.length - 1]
/*获取该ele的最后一个子节点*/
const lastNode = element.children[element.children.length - 1]
/*该子节点是非<pre>标签的文本*/
if (lastNode && lastNode.type === 3 && lastNode.text === ' ' && !inPre) {
element.children.pop()
}
// pop stack
/*ele出栈*/
stack.length -= 1
currentParent = stack[stack.length - 1]
endPre(element)
},
chars (text: string) {
if (!currentParent) {
if (process.env.NODE_ENV !== 'production') {
if (text === template) {
warnOnce(
'Component template requires a root element, rather than just text.'
)
} else if ((text = text.trim())) {
warnOnce(
`text "${text}" outside root element will be ignored.`
)
}
}
return
}
// IE textarea placeholder bug
/* istanbul ignore if */
if (isIE &&
currentParent.tag === 'textarea' &&
currentParent.attrsMap.placeholder === text) {
return
}
const children = currentParent.children
text = inPre || text.trim()
? isTextTag(currentParent) ? text : decodeHTMLCached(text)
// only preserve whitespace if its not right after a starting tag
: preserveWhitespace && children.length ? ' ' : ''
if (text) {
let expression
if (!inVPre && text !== ' ' && (expression = parseText(text, delimiters))) {
children.push({
type: 2,
expression,
text
})
} else if (text !== ' ' || !children.length || children[children.length - 1].text !== ' ') {
children.push({
type: 3,
text
})
}
}
}
})
return root
}
/*
处理v-pre属性
v-pre元素及其子元素被跳过编译
https://cn.vuejs.org/v2/api/#v-pre
*/
function processPre (el) {
if (getAndRemoveAttr(el, 'v-pre') != null) {
el.pre = true
}
}
/*处理原生属性,将其放入attrs中,以{name, value}的形式*/
function processRawAttrs (el) {
const l = el.attrsList.length
if (l) {
const attrs = el.attrs = new Array(l)
for (let i = 0; i < l; i++) {
attrs[i] = {
name: el.attrsList[i].name,
value: JSON.stringify(el.attrsList[i].value)
}
}
} else if (!el.pre) {
// non root node in pre blocks with no attributes
el.plain = true
}
}
/*处理key属性 https://cn.vuejs.org/v2/api/#key*/
function processKey (el) {
const exp = getBindingAttr(el, 'key')
if (exp) {
if (process.env.NODE_ENV !== 'production' && el.tag === 'template') {
warn(`<template> cannot be keyed. Place the key on real elements instead.`)
}
el.key = exp
}
}
/*处理ref属性 https://cn.vuejs.org/v2/api/#ref*/
function processRef (el) {
const ref = getBindingAttr(el, 'ref')
if (ref) {
el.ref = ref
/*
检测该元素是否存在一个for循环中。
将会沿着parent元素一级一级向上便利寻找是否处于一个for循环中。
当 v-for 用于元素或组件的时候,引用信息将是包含 DOM 节点或组件实例的数组。
*/
el.refInFor = checkInFor(el)
}
}
/*匹配v-for属性*/
function processFor (el) {
let exp
/*取出v-for属性*/
if ((exp = getAndRemoveAttr(el, 'v-for'))) {
/*匹配v-for中的in以及of 以item in sz为例 inMatch = [ 'item of sz', 'item', 'sz', index: 0, input: 'item of sz' ]*/
const inMatch = exp.match(forAliasRE)
/*匹配失败则在非生产环境中打印v-for的无效表达式*/
if (!inMatch) {
process.env.NODE_ENV !== 'production' && warn(
`Invalid v-for expression: ${exp}`
)
return
}
/*在这里是sz*/
el.for = inMatch[2].trim()
/*item*/
const alias = inMatch[1].trim()
/*
因为item可能是被括号包裹的,比如(item, index) in sz这样的形式,匹配出这些项
例:(item, index)匹配得到结果
[ '(item, index, l)',
'item',
' index',
l,
index: 0,
input: '(item, index, l);' ]
*/
const iteratorMatch = alias.match(forIteratorRE)
if (iteratorMatch) {
el.alias = iteratorMatch[1].trim()
el.iterator1 = iteratorMatch[2].trim()
if (iteratorMatch[3]) {
el.iterator2 = iteratorMatch[3].trim()
}
} else {
el.alias = alias
}
}
}
/*匹配if属性,分别处理v-if、v-else以及v-else-if属性*/
function processIf (el) {
/*取出v-if属性*/
const exp = getAndRemoveAttr(el, 'v-if')
if (exp) {
/*存在v-if属性*/
el.if = exp
/*在el的ifConditions属性中加入{exp, block}*/
addIfCondition(el, {
exp: exp,
block: el
})
} else {
/*不存在v-if属性*/
if (getAndRemoveAttr(el, 'v-else') != null) {
el.else = true
}
const elseif = getAndRemoveAttr(el, 'v-else-if')
if (elseif) {
el.elseif = elseif
}
}
}
/*处理if条件*/
function processIfConditions (el, parent) {
/*当遇到当前ele有v-else或者v-elseif属性的时候,需要处理if属性,在其上级兄弟元素中必然存在v-if属性*/
const prev = findPrevElement(parent.children)
if (prev && prev.if) {
addIfCondition(prev, {
exp: el.elseif,
block: el
})
} else if (process.env.NODE_ENV !== 'production') {
warn(
`v-${el.elseif ? ('else-if="' + el.elseif + '"') : 'else'} ` +
`used on element <${el.tag}> without corresponding v-if.`
)
}
}
/*找到上一个ele*/
function findPrevElement (children: Array<any>): ASTElement | void {
let i = children.length
while (i--) {
if (children[i].type === 1) {
return children[i]
} else {
if (process.env.NODE_ENV !== 'production' && children[i].text !== ' ') {
warn(
`text "${children[i].text.trim()}" between v-if and v-else(-if) ` +
`will be ignored.`
)
}
children.pop()
}
}
}
/*在el的ifConditions属性中加入condition*/
function addIfCondition (el, condition) {
if (!el.ifConditions) {
el.ifConditions = []
}
el.ifConditions.push(condition)
}
/*处理v-once属性,https://cn.vuejs.org/v2/api/#v-once*/
function processOnce (el) {
const once = getAndRemoveAttr(el, 'v-once')
if (once != null) {
el.once = true
}
}
/*处理slot属性 https://cn.vuejs.org/v2/api/#slot*/
function processSlot (el) {
if (el.tag === 'slot') {
/*获取name特殊属性:name或者bind:name,用作slot的name https://cn.vuejs.org/v2/api/#slot-1*/
el.slotName = getBindingAttr(el, 'name')
if (process.env.NODE_ENV !== 'production' && el.key) {
warn(
`\`key\` does not work on <slot> because slots are abstract outlets ` +
`and can possibly expand into multiple elements. ` +
`Use the key on a wrapping element instead.`
)
}
} else {
/*获取属性为slot的slot https://cn.vuejs.org/v2/api/#slot*/
const slotTarget = getBindingAttr(el, 'slot')
if (slotTarget) {
el.slotTarget = slotTarget === '""' ? '"default"' : slotTarget
}
if (el.tag === 'template') {
el.slotScope = getAndRemoveAttr(el, 'scope')
}
}
}
/*处理组件*/
function processComponent (el) {
let binding
/*获取is属性,用于动态动态组件 https://cn.vuejs.org/v2/api/#is */
if ((binding = getBindingAttr(el, 'is'))) {
el.component = binding
}
/*inline-template 内置组件 https://cn.vuejs.org/v2/api/#内置的组件*/
if (getAndRemoveAttr(el, 'inline-template') != null) {
el.inlineTemplate = true
}
}
/*处理属性*/
function processAttrs (el) {
/*获取元素属性列表*/
const list = el.attrsList
let i, l, name, rawName, value, modifiers, isProp
for (i = 0, l = list.length; i < l; i++) {
name = rawName = list[i].name
value = list[i].value
/*匹配v-、@以及:,处理ele的特殊属性*/
if (dirRE.test(name)) {
/*标记该ele为动态的*/
// mark element as dynamic
el.hasBindings = true
// modifiers
/*解析表达式,比如a.b.c.d得到结果{b: true, c: true, d:true}*/
modifiers = parseModifiers(name)
if (modifiers) {
/*得到第一级,比如a.b.c.d得到a,也就是上面的操作把所有子级取出来,这个把第一级取出来*/
name = name.replace(modifierRE, '')
}
/*如果属性是v-bind的*/
if (bindRE.test(name)) { // v-bind
/*这样处理以后v-bind:aaa得到aaa*/
name = name.replace(bindRE, '')
/*解析过滤器*/
value = parseFilters(value)
isProp = false
if (modifiers) {
/*
https://cn.vuejs.org/v2/api/#v-bind
这里用来处理v-bind的修饰符
*/
/*.prop - 被用于绑定 DOM 属性。*/
if (modifiers.prop) {
isProp = true
/*将原本用-连接的字符串变成驼峰 aaa-bbb-ccc => aaaBbbCcc*/
name = camelize(name)
if (name === 'innerHtml') name = 'innerHTML'
}
/*.camel - (2.1.0+) 将 kebab-case 特性名转换为 camelCase. (从 2.1.0 开始支持)*/
if (modifiers.camel) {
name = camelize(name)
}
//.sync (2.3.0+) 语法糖,会扩展成一个更新父组件绑定值的 v-on 侦听器。
if (modifiers.sync) {
addHandler(
el,
`update:${camelize(name)}`,
genAssignmentCode(value, `$event`)
)
}
}
if (isProp || platformMustUseProp(el.tag, el.attrsMap.type, name)) {
/*将属性放入ele的props属性中*/
addProp(el, name, value)
} else {
/*将属性放入ele的attr属性中*/
addAttr(el, name, value)
}
} else if (onRE.test(name)) { // v-on
/*处理v-on以及bind*/
name = name.replace(onRE, '')
addHandler(el, name, value, modifiers, false, warn)
} else { // normal directives
/*去除@、:、v-*/
name = name.replace(dirRE, '')
// parse arg
const argMatch = name.match(argRE)
/*比如:fun="functionA"解析出fun="functionA"*/
const arg = argMatch && argMatch[1]
if (arg) {
name = name.slice(0, -(arg.length + 1))
}
/*将参数加入到ele的directives中去*/
addDirective(el, name, rawName, value, arg, modifiers)
if (process.env.NODE_ENV !== 'production' && name === 'model') {
checkForAliasModel(el, value)
}
}
} else {
/*处理常规的字符串属性*/
// literal attribute
if (process.env.NODE_ENV !== 'production') {
const expression = parseText(value, delimiters)
if (expression) {
/*
插入属性内部会被删除,请改用冒号或者v-bind
比如应该用<div :id="test">来代替<div id="{{test}}">
*/
warn(
`${name}="${value}": ` +
'Interpolation inside attributes has been removed. ' +
'Use v-bind or the colon shorthand instead. For example, ' +
'instead of <div id="{{ val }}">, use <div :id="val">.'
)
}
}
/*将属性放入ele的attr属性中*/
addAttr(el, name, JSON.stringify(value))
}
}
}
/*检测该元素是否存在一个for循环中,将会沿着parent元素一级一级向上便利寻找是否处于一个for循环中。*/
function checkInFor (el: ASTElement): boolean {
let parent = el
while (parent) {
if (parent.for !== undefined) {
return true
}
parent = parent.parent
}
return false
}
/*解析表达式,比如a.b.c.d得到结果{b: true, c: true, d:true}*/
function parseModifiers (name: string): Object | void {
/*根据点来分开各个级别的正则,比如a.b.c.d解析后可以得到.b .c .d*/
const match = name.match(modifierRE)
if (match) {
const ret = {}
match.forEach(m => { ret[m.slice(1)] = true })
return ret
}
}
function makeAttrsMap (attrs: Array<Object>): Object {
const map = {}
for (let i = 0, l = attrs.length; i < l; i++) {
if (
process.env.NODE_ENV !== 'production' &&
map[attrs[i].name] && !isIE && !isEdge
) {
warn('duplicate attribute: ' + attrs[i].name)
}
map[attrs[i].name] = attrs[i].value
}
return map
}
// for script (e.g. type="x/template") or style, do not decode content
function isTextTag (el): boolean {
return el.tag === 'script' || el.tag === 'style'
}
/*判断是否是被禁止的标签(style标签或者script标签)*/
function isForbiddenTag (el): boolean {
return (
el.tag === 'style' ||
(el.tag === 'script' && (
!el.attrsMap.type ||
el.attrsMap.type === 'text/javascript'
))
)
}
const ieNSBug = /^xmlns:NS\d+/
const ieNSPrefix = /^NS\d+:/
/* istanbul ignore next */
function guardIESVGBug (attrs) {
const res = []
for (let i = 0; i < attrs.length; i++) {
const attr = attrs[i]
if (!ieNSBug.test(attr.name)) {
attr.name = attr.name.replace(ieNSPrefix, '')
res.push(attr)
}
}
return res
}
function checkForAliasModel (el, value) {
let _el = el
while (_el) {
if (_el.for && _el.alias === value) {
warn(
`<${el.tag} v-model="${value}">: ` +
`You are binding v-model directly to a v-for iteration alias. ` +
`This will not be able to modify the v-for source array because ` +
`writing to the alias is like modifying a function local variable. ` +
`Consider using an array of objects and use v-model on an object property instead.`
)
}
_el = _el.parent
}
}