text: /* @flow */
  
  import he from 'he'
  import { parseHTML } from './html-parser'
  import { parseText } from './text-parser'
  import { parseFilters } from './filter-parser'
  import { genAssignmentCode } from '../directives/model'
  import { extend, cached, no, camelize, hyphenate } from 'shared/util'
  import { isIE, isEdge, isServerRendering } from 'core/util/env'
  
  import {
    addProp,
    addAttr,
    baseWarn,
    addHandler,
    addDirective,
    getBindingAttr,
    getAndRemoveAttr,
    getRawBindingAttr,
    pluckModuleFunction,
    getAndRemoveAttrByRegex
  } from '../helpers'
  
  export const onRE = /^@|^v-on:/
  export const dirRE = process.env.VBIND_PROP_SHORTHAND
    ? /^v-|^@|^:|^\.|^#/
    : /^v-|^@|^:|^#/
  export const forAliasRE = /([\s\S]*?)\s+(?:in|of)\s+([\s\S]*)/
  export const forIteratorRE = /,([^,\}\]]*)(?:,([^,\}\]]*))?$/
  const stripParensRE = /^\(|\)$/g
  const dynamicArgRE = /^\[.*\]$/
  
  const argRE = /:(.*)$/
  export const bindRE = /^:|^\.|^v-bind:/
  const propBindRE = /^\./
  const modifierRE = /\.[^.\]]+(?=[^\]]*$)/g
  
  const slotRE = /^v-slot(:|$)|^#/
  
  const lineBreakRE = /[\r\n]/
  const whitespaceRE = /\s+/g
  
  const invalidAttributeRE = /[\s"'<>\/=]/
  
  const decodeHTMLCached = cached(he.decode)
  
  export const emptySlotScopeToken = `_empty_`
  
  // configurable state
  export let warn: any
  let delimiters
  let transforms
  let preTransforms
  let postTransforms
  let platformIsPreTag
  let platformMustUseProp
  let platformGetTagNamespace
  let maybeComponent
  
  export function createASTElement (
    tag: string,
    attrs: Array<ASTAttr>,
    parent: ASTElement | void
  ): ASTElement {
    return {
      type: 1,
      tag,
      attrsList: attrs,
      attrsMap: makeAttrsMap(attrs),
      rawAttrsMap: {},
      parent,
      children: []
    }
  }
  
   // 解析 template 模板, 把模板解析成 AST
  export function parse (
    template: string,
    options: CompilerOptions
  ): ASTElement | void {
    warn = options.warn || baseWarn
  
    platformIsPreTag = options.isPreTag || no
    platformMustUseProp = options.mustUseProp || no
    platformGetTagNamespace = options.getTagNamespace || no
    const isReservedTag = options.isReservedTag || no
    maybeComponent = (el: ASTElement) => !!el.component || !isReservedTag(el.tag)
  
    transforms = pluckModuleFunction(options.modules, 'transformNode')
    preTransforms = pluckModuleFunction(options.modules, 'preTransformNode')
    postTransforms = pluckModuleFunction(options.modules, 'postTransformNode')
  
    delimiters = options.delimiters
  
    const stack = []
    const preserveWhitespace = options.preserveWhitespace !== false
    const whitespaceOption = options.whitespace
    let root
    let currentParent
    let inVPre = false
    let inPre = false
    let warned = false
  
    function warnOnce (msg, range) {
      if (!warned) {
        warned = true
        warn(msg, range)
      }
    }
  
    function closeElement (element) {
      trimEndingWhitespace(element)
      if (!inVPre && !element.processed) {
        element = processElement(element, options)
      }
      // tree management
      if (!stack.length && element !== root) {
        // allow root elements with v-if, v-else-if and v-else
        if (root.if && (element.elseif || element.else)) {
          if (process.env.NODE_ENV !== 'production') {
            checkRootConstraints(element)
          }
          addIfCondition(root, {
            exp: element.elseif,
            block: element
          })
        } else if (process.env.NODE_ENV !== 'production') {
          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.`,
            { start: element.start }
          )
        }
      }
      if (currentParent && !element.forbidden) {
        if (element.elseif || element.else) {
          processIfConditions(element, currentParent)
        } else {
          if (element.slotScope) {
            // scoped slot
            // keep it in the children list so that v-else(-if) conditions can
            // find it as the prev node.
            const name = element.slotTarget || '"default"'
            ;(currentParent.scopedSlots || (currentParent.scopedSlots = {}))[name] = element
          }
          currentParent.children.push(element)
          element.parent = currentParent
        }
      }
  
      // final children cleanup
      // filter out scoped slots
      element.children = element.children.filter(c => !(c: any).slotScope)
      // remove trailing whitespace node again
      trimEndingWhitespace(element)
  
      // check pre state
      if (element.pre) {
        inVPre = false
      }
      if (platformIsPreTag(element.tag)) {
        inPre = false
      }
      // apply post-transforms
      for (let i = 0; i < postTransforms.length; i++) {
        postTransforms[i](element, options)
      }
    }
  
    function trimEndingWhitespace (el) {
      // remove trailing whitespace node
      if (!inPre) {
        let lastNode
        while (
          (lastNode = el.children[el.children.length - 1]) &&
          lastNode.type === 3 &&
          lastNode.text === ' '
        ) {
          el.children.pop()
        }
      }
    }
  
    function checkRootConstraints (el) {
      if (el.tag === 'slot' || el.tag === 'template') {
        warnOnce(
          `Cannot use <${el.tag}> as component root element because it may ` +
          'contain multiple nodes.',
          { start: el.start }
        )
      }
      if (el.attrsMap.hasOwnProperty('v-for')) {
        warnOnce(
          'Cannot use v-for on stateful component root element because ' +
          'it renders multiple elements.',
          el.rawAttrsMap['v-for']
        )
      }
    }
  
    parseHTML(template, {
      warn,
      expectHTML: options.expectHTML,
      isUnaryTag: options.isUnaryTag,
      canBeLeftOpenTag: options.canBeLeftOpenTag,
      shouldDecodeNewlines: options.shouldDecodeNewlines,
      shouldDecodeNewlinesForHref: options.shouldDecodeNewlinesForHref,
      shouldKeepComment: options.comments,
      outputSourceRange: options.outputSourceRange,
      start (tag, attrs, unary, start, end) {
        // check namespace.
        // inherit parent ns if there is one
        // 获取 namespace
        const ns = (currentParent && currentParent.ns) || platformGetTagNamespace(tag)
  
        /* istanbul ignore if */
        // 处理 IE svg 问题
        if (isIE && ns === 'svg') {
          attrs = guardIESVGBug(attrs)
        }
  
        let element: ASTElement = createASTElement(tag, attrs, currentParent)
        if (ns) {
          element.ns = ns
        }
  
        if (process.env.NODE_ENV !== 'production') {
          if (options.outputSourceRange) {
            element.start = start
            element.end = end
            element.rawAttrsMap = element.attrsList.reduce((cumulated, attr) => {
              cumulated[attr.name] = attr
              return cumulated
            }, {})
          }
          attrs.forEach(attr => {
            if (invalidAttributeRE.test(attr.name)) {
              warn(
                `Invalid dynamic argument expression: attribute names cannot contain ` +
                `spaces, quotes, <, >, / or =.`,
                {
                  start: attr.start + attr.name.indexOf(`[`),
                  end: attr.start + attr.name.length
                }
              )
            }
          })
        }
  
        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.',
            { start: element.start }
          )
        }
  
        // apply pre-transforms
        for (let i = 0; i < preTransforms.length; i++) {
          element = preTransforms[i](element, options) || element
        }
  
        if (!inVPre) {
          processPre(element)
          if (element.pre) {
            inVPre = true
          }
        }
        if (platformIsPreTag(element.tag)) {
          inPre = true
        }
        if (inVPre) {
          processRawAttrs(element)
        } else if (!element.processed) {
          // structural directives
          processFor(element)
          processIf(element)
          processOnce(element)
        }
  
        if (!root) {
          root = element
          if (process.env.NODE_ENV !== 'production') {
            checkRootConstraints(root)
          }
        }
  
        if (!unary) {
          currentParent = element
          stack.push(element)
        } else {
          closeElement(element)
        }
      },
  
      end (tag, start, end) {
        const element = stack[stack.length - 1]
        // pop stack
        stack.length -= 1
        currentParent = stack[stack.length - 1]
        if (process.env.NODE_ENV !== 'production' && options.outputSourceRange) {
          element.end = end
        }
        closeElement(element)
      },
  
      chars (text: string, start: number, end: number) {
        if (!currentParent) {
          if (process.env.NODE_ENV !== 'production') {
            if (text === template) {
              warnOnce(
                'Component template requires a root element, rather than just text.',
                { start }
              )
            } else if ((text = text.trim())) {
              warnOnce(
                `text "${text}" outside root element will be ignored.`,
                { start }
              )
            }
          }
          return
        }
        // IE textarea placeholder bug
        /* istanbul ignore if */
        if (isIE &&
          currentParent.tag === 'textarea' &&
          currentParent.attrsMap.placeholder === text
        ) {
          return
        }
        const children = currentParent.children
        if (inPre || text.trim()) {
          text = isTextTag(currentParent) ? text : decodeHTMLCached(text)
        } else if (!children.length) {
          // remove the whitespace-only node right after an opening tag
          text = ''
        } else if (whitespaceOption) {
          if (whitespaceOption === 'condense') {
            // in condense mode, remove the whitespace node if it contains
            // line break, otherwise condense to a single space
            text = lineBreakRE.test(text) ? '' : ' '
          } else {
            text = ' '
          }
        } else {
          text = preserveWhitespace ? ' ' : ''
        }
        if (text) {
          if (!inPre && whitespaceOption === 'condense') {
            // condense consecutive whitespaces into single space
            text = text.replace(whitespaceRE, ' ')
          }
          let res
          let child: ?ASTNode
          if (!inVPre && text !== ' ' && (res = parseText(text, delimiters))) {
            child = {
              type: 2,
              expression: res.expression,
              tokens: res.tokens,
              text
            }
          } else if (text !== ' ' || !children.length || children[children.length - 1].text !== ' ') {
            child = {
              type: 3,
              text
            }
          }
          if (child) {
            if (process.env.NODE_ENV !== 'production' && options.outputSourceRange) {
              child.start = start
              child.end = end
            }
            children.push(child)
          }
        }
      },
      comment (text: string, start, end) {
        // adding anything as a sibling to the root node is forbidden
        // comments should still be allowed, but ignored
        if (currentParent) {
          const child: ASTText = {
            type: 3,
            text,
            isComment: true
          }
          if (process.env.NODE_ENV !== 'production' && options.outputSourceRange) {
            child.start = start
            child.end = end
          }
          currentParent.children.push(child)
        }
      }
    })
    return root
  }
  
  function processPre (el) {
    if (getAndRemoveAttr(el, 'v-pre') != null) {
      el.pre = true
    }
  }
  
  function processRawAttrs (el) {
    const list = el.attrsList
    const len = list.length
    if (len) {
      const attrs: Array<ASTAttr> = el.attrs = new Array(len)
      for (let i = 0; i < len; i++) {
        attrs[i] = {
          name: list[i].name,
          value: JSON.stringify(list[i].value)
        }
        if (list[i].start != null) {
          attrs[i].start = list[i].start
          attrs[i].end = list[i].end
        }
      }
    } else if (!el.pre) {
      // non root node in pre blocks with no attributes
      el.plain = true
    }
  }
  
  export function processElement (
    element: ASTElement,
    options: CompilerOptions
  ) {
    processKey(element)
  
    // determine whether this is a plain element after
    // removing structural attributes
    element.plain = (
      !element.key &&
      !element.scopedSlots &&
      !element.attrsList.length
    )
  
    processRef(element)
    processSlotContent(element)
    processSlotOutlet(element)
    processComponent(element)
    for (let i = 0; i < transforms.length; i++) {
      element = transforms[i](element, options) || element
    }
    processAttrs(element)
    return element
  }
  
  function processKey (el) {
    const exp = getBindingAttr(el, 'key')
    if (exp) {
      if (process.env.NODE_ENV !== 'production') {
        if (el.tag === 'template') {
          warn(
            `<template> cannot be keyed. Place the key on real elements instead.`,
            getRawBindingAttr(el, 'key')
          )
        }
        if (el.for) {
          const iterator = el.iterator2 || el.iterator1
          const parent = el.parent
          if (iterator && iterator === exp && parent && parent.tag === 'transition-group') {
            warn(
              `Do not use v-for index as key on <transition-group> children, ` +
              `this is the same as not using keys.`,
              getRawBindingAttr(el, 'key'),
              true /* tip */
            )
          }
        }
      }
      el.key = exp
    }
  }
  
  function processRef (el) {
    const ref = getBindingAttr(el, 'ref')
    if (ref) {
      el.ref = ref
      el.refInFor = checkInFor(el)
    }
  }
  
  export function processFor (el: ASTElement) {
    let exp
    if ((exp = getAndRemoveAttr(el, 'v-for'))) {
      const res = parseFor(exp)
      if (res) {
        extend(el, res)
      } else if (process.env.NODE_ENV !== 'production') {
        warn(
          `Invalid v-for expression: ${exp}`,
          el.rawAttrsMap['v-for']
        )
      }
    }
  }
  
  type ForParseResult = {
    for: string;
    alias: string;
    iterator1?: string;
    iterator2?: string;
  };
  
  export function parseFor (exp: string): ?ForParseResult {
    const inMatch = exp.match(forAliasRE)
    if (!inMatch) return
    const res = {}
    res.for = inMatch[2].trim()
    const alias = inMatch[1].trim().replace(stripParensRE, '')
    const iteratorMatch = alias.match(forIteratorRE)
    if (iteratorMatch) {
      res.alias = alias.replace(forIteratorRE, '').trim()
      res.iterator1 = iteratorMatch[1].trim()
      if (iteratorMatch[2]) {
        res.iterator2 = iteratorMatch[2].trim()
      }
    } else {
      res.alias = alias
    }
    return res
  }
  
  function processIf (el) {
    const exp = getAndRemoveAttr(el, 'v-if')
    if (exp) {
      el.if = exp
      addIfCondition(el, {
        exp: exp,
        block: el
      })
    } else {
      if (getAndRemoveAttr(el, 'v-else') != null) {
        el.else = true
      }
      const elseif = getAndRemoveAttr(el, 'v-else-if')
      if (elseif) {
        el.elseif = elseif
      }
    }
  }
  
  function processIfConditions (el, parent) {
    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.`,
        el.rawAttrsMap[el.elseif ? 'v-else-if' : 'v-else']
      )
    }
  }
  
  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[i]
          )
        }
        children.pop()
      }
    }
  }
  
  export function addIfCondition (el: ASTElement, condition: ASTIfCondition) {
    if (!el.ifConditions) {
      el.ifConditions = []
    }
    el.ifConditions.push(condition)
  }
  
  function processOnce (el) {
    const once = getAndRemoveAttr(el, 'v-once')
    if (once != null) {
      el.once = true
    }
  }
  
  // handle content being passed to a component as slot,
  // e.g. <template slot="xxx">, <div slot-scope="xxx">
  function processSlotContent (el) {
    let slotScope
    if (el.tag === 'template') {
      slotScope = getAndRemoveAttr(el, 'scope')
      /* istanbul ignore if */
      if (process.env.NODE_ENV !== 'production' && slotScope) {
        warn(
          `the "scope" attribute for scoped slots have been deprecated and ` +
          `replaced by "slot-scope" since 2.5. The new "slot-scope" attribute ` +
          `can also be used on plain elements in addition to <template> to ` +
          `denote scoped slots.`,
          el.rawAttrsMap['scope'],
          true
        )
      }
      el.slotScope = slotScope || getAndRemoveAttr(el, 'slot-scope')
    } else if ((slotScope = getAndRemoveAttr(el, 'slot-scope'))) {
      /* istanbul ignore if */
      if (process.env.NODE_ENV !== 'production' && el.attrsMap['v-for']) {
        warn(
          `Ambiguous combined usage of slot-scope and v-for on <${el.tag}> ` +
          `(v-for takes higher priority). Use a wrapper <template> for the ` +
          `scoped slot to make it clearer.`,
          el.rawAttrsMap['slot-scope'],
          true
        )
      }
      el.slotScope = slotScope
    }
  
    // slot="xxx"
    const slotTarget = getBindingAttr(el, 'slot')
    if (slotTarget) {
      el.slotTarget = slotTarget === '""' ? '"default"' : slotTarget
      el.slotTargetDynamic = !!(el.attrsMap[':slot'] || el.attrsMap['v-bind:slot'])
      // preserve slot as an attribute for native shadow DOM compat
      // only for non-scoped slots.
      if (el.tag !== 'template' && !el.slotScope) {
        addAttr(el, 'slot', slotTarget, getRawBindingAttr(el, 'slot'))
      }
    }
  
    // 2.6 v-slot syntax
    if (process.env.NEW_SLOT_SYNTAX) {
      if (el.tag === 'template') {
        // v-slot on <template>
        const slotBinding = getAndRemoveAttrByRegex(el, slotRE)
        if (slotBinding) {
          if (process.env.NODE_ENV !== 'production') {
            if (el.slotTarget || el.slotScope) {
              warn(
                `Unexpected mixed usage of different slot syntaxes.`,
                el
              )
            }
            if (el.parent && !maybeComponent(el.parent)) {
              warn(
                `<template v-slot> can only appear at the root level inside ` +
                `the receiving component`,
                el
              )
            }
          }
          const { name, dynamic } = getSlotName(slotBinding)
          el.slotTarget = name
          el.slotTargetDynamic = dynamic
          el.slotScope = slotBinding.value || emptySlotScopeToken // force it into a scoped slot for perf
        }
      } else {
        // v-slot on component, denotes default slot
        const slotBinding = getAndRemoveAttrByRegex(el, slotRE)
        if (slotBinding) {
          if (process.env.NODE_ENV !== 'production') {
            if (!maybeComponent(el)) {
              warn(
                `v-slot can only be used on components or <template>.`,
                slotBinding
              )
            }
            if (el.slotScope || el.slotTarget) {
              warn(
                `Unexpected mixed usage of different slot syntaxes.`,
                el
              )
            }
            if (el.scopedSlots) {
              warn(
                `To avoid scope ambiguity, the default slot should also use ` +
                `<template> syntax when there are other named slots.`,
                slotBinding
              )
            }
          }
          // add the component's children to its default slot
          const slots = el.scopedSlots || (el.scopedSlots = {})
          const { name, dynamic } = getSlotName(slotBinding)
          const slotContainer = slots[name] = createASTElement('template', [], el)
          slotContainer.slotTarget = name
          slotContainer.slotTargetDynamic = dynamic
          slotContainer.children = el.children.filter((c: any) => {
            if (!c.slotScope) {
              c.parent = slotContainer
              return true
            }
          })
          slotContainer.slotScope = slotBinding.value || emptySlotScopeToken
          // remove children as they are returned from scopedSlots now
          el.children = []
          // mark el non-plain so data gets generated
          el.plain = false
        }
      }
    }
  }
  
  function getSlotName (binding) {
    let name = binding.name.replace(slotRE, '')
    if (!name) {
      if (binding.name[0] !== '#') {
        name = 'default'
      } else if (process.env.NODE_ENV !== 'production') {
        warn(
          `v-slot shorthand syntax requires a slot name.`,
          binding
        )
      }
    }
    return dynamicArgRE.test(name)
      // dynamic [name]
      ? { name: name.slice(1, -1), dynamic: true }
      // static name
      : { name: `"${name}"`, dynamic: false }
  }
  
  // handle <slot/> outlets
  function processSlotOutlet (el) {
    if (el.tag === 'slot') {
      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.`,
          getRawBindingAttr(el, 'key')
        )
      }
    }
  }
  
  function processComponent (el) {
    let binding
    if ((binding = getBindingAttr(el, 'is'))) {
      el.component = binding
    }
    if (getAndRemoveAttr(el, 'inline-template') != null) {
      el.inlineTemplate = true
    }
  }
  
  function processAttrs (el) {
    const list = el.attrsList
    let i, l, name, rawName, value, modifiers, syncGen, isDynamic
    for (i = 0, l = list.length; i < l; i++) {
      name = rawName = list[i].name
      value = list[i].value
      if (dirRE.test(name)) {
        // mark element as dynamic
        el.hasBindings = true
        // modifiers
        modifiers = parseModifiers(name.replace(dirRE, ''))
        // support .foo shorthand syntax for the .prop modifier
        if (process.env.VBIND_PROP_SHORTHAND && propBindRE.test(name)) {
          (modifiers || (modifiers = {})).prop = true
          name = `.` + name.slice(1).replace(modifierRE, '')
        } else if (modifiers) {
          name = name.replace(modifierRE, '')
        }
        if (bindRE.test(name)) { // v-bind
          name = name.replace(bindRE, '')
          value = parseFilters(value)
          isDynamic = dynamicArgRE.test(name)
          if (isDynamic) {
            name = name.slice(1, -1)
          }
          if (
            process.env.NODE_ENV !== 'production' &&
            value.trim().length === 0
          ) {
            warn(
              `The value for a v-bind expression cannot be empty. Found in "v-bind:${name}"`
            )
          }
          if (modifiers) {
            if (modifiers.prop && !isDynamic) {
              name = camelize(name)
              if (name === 'innerHtml') name = 'innerHTML'
            }
            if (modifiers.camel && !isDynamic) {
              name = camelize(name)
            }
            if (modifiers.sync) {
              syncGen = genAssignmentCode(value, `$event`)
              if (!isDynamic) {
                addHandler(
                  el,
                  `update:${camelize(name)}`,
                  syncGen,
                  null,
                  false,
                  warn,
                  list[i]
                )
                if (hyphenate(name) !== camelize(name)) {
                  addHandler(
                    el,
                    `update:${hyphenate(name)}`,
                    syncGen,
                    null,
                    false,
                    warn,
                    list[i]
                  )
                }
              } else {
                // handler w/ dynamic event name
                addHandler(
                  el,
                  `"update:"+(${name})`,
                  syncGen,
                  null,
                  false,
                  warn,
                  list[i],
                  true // dynamic
                )
              }
            }
          }
          if ((modifiers && modifiers.prop) || (
            !el.component && platformMustUseProp(el.tag, el.attrsMap.type, name)
          )) {
            addProp(el, name, value, list[i], isDynamic)
          } else {
            addAttr(el, name, value, list[i], isDynamic)
          }
        } else if (onRE.test(name)) { // v-on
          name = name.replace(onRE, '')
          isDynamic = dynamicArgRE.test(name)
          if (isDynamic) {
            name = name.slice(1, -1)
          }
          addHandler(el, name, value, modifiers, false, warn, list[i], isDynamic)
        } else { // normal directives
          name = name.replace(dirRE, '')
          // parse arg
          const argMatch = name.match(argRE)
          let arg = argMatch && argMatch[1]
          isDynamic = false
          if (arg) {
            name = name.slice(0, -(arg.length + 1))
            if (dynamicArgRE.test(arg)) {
              arg = arg.slice(1, -1)
              isDynamic = true
            }
          }
          addDirective(el, name, rawName, value, arg, isDynamic, modifiers, list[i])
          if (process.env.NODE_ENV !== 'production' && name === 'model') {
            checkForAliasModel(el, value)
          }
        }
      } else {
        // literal attribute
        if (process.env.NODE_ENV !== 'production') {
          const res = parseText(value, delimiters)
          if (res) {
            warn(
              `${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">.',
              list[i]
            )
          }
        }
        addAttr(el, name, JSON.stringify(value), list[i])
        // #6887 firefox doesn't update muted state if set via attribute
        // even immediately after element creation
        if (!el.component &&
            name === 'muted' &&
            platformMustUseProp(el.tag, el.attrsMap.type, name)) {
          addProp(el, name, 'true', list[i])
        }
      }
    }
  }
  
  function checkInFor (el: ASTElement): boolean {
    let parent = el
    while (parent) {
      if (parent.for !== undefined) {
        return true
      }
      parent = parent.parent
    }
    return false
  }
  
  function parseModifiers (name: string): Object | void {
    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, attrs[i])
      }
      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'
  }
  
  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.rawAttrsMap['v-model']
        )
      }
      _el = _el.parent
    }
  }
  