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bc89f92 Feb 7, 2019
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AST for <template lang="html">

Some types are featured from ESTree.

You can use the type definition of this AST:

import { AST } from "vue-eslint-parser"

export function create(context) {
    return context.parserServices.defineTemplateBodyVisitor(
        // Event handlers for <template>.
            VElement(node: AST.VElement): void {
        // Event handlers for <script>. (optional)
            Program(node: AST.ESLintProgram): void {

AST has the types of ESLint's AST with the prefix ESLint.
See details: ../src/ast/nodes.ts


extend interface Node {
    range: [ number ]
  • This AST spec enhances the Node nodes like ESLint.
  • The range property is an array which has 2 integers. The 1st integer is the offset of the start location of the node. The 2nd integer is the offset of the end location of the node.


interface VIdentifier <: Node {
    type: "VIdentifier"
    name: string
    rawName: string
  • This is similar to Identifier nodes but this name property can include any characters except U+0000-U+001F, U+007F-U+009F, U+0020, U+0022, U+0027, U+003E, U+002F, U+003D, U+FDD0-U+FDEF, U+FFFE, U+FFFF, U+1FFFE, U+1FFFF, U+2FFFE, U+2FFFF, U+3FFFE, U+3FFFF, U+4FFFE, U+4FFFF, U+5FFFE, U+5FFFF, U+6FFFE, U+6FFFF, U+7FFFE, U+7FFFF, U+8FFFE, U+8FFFF, U+9FFFE, U+9FFFF, U+AFFFE, U+AFFFF, U+BFFFE, U+BFFFF, U+CFFFE, U+CFFFF, U+DFFFE, U+DFFFF, U+EFFFE, U+EFFFF, U+FFFFE, U+FFFFF, U+10FFFE and U+10FFFF.
  • This is attribute names.


interface VText <: Node {
    type: "VText"
    value: string
  • Plain text of HTML.
  • HTML entities in the value property are decoded.


interface VExpressionContainer <: Node {
    type: "VExpressionContainer"
    expression: Expression | null
    references: [ Reference ]

interface Reference {
    id: Identifier
    mode: "rw" | "r" | "w"
    variable: Variable | null

interface VForExpression <: Expression {
    type: "VForExpression"
    left: [ Pattern ]
    right: Expression

interface VOnExpression <: Expression {
    type: "VOnExpression"
    body: [ Statement ]

interface VSlotScopeExpression <: Expression {
    type: "VSlotScopeExpression"
    params: [ Pattern | RestElement ]

interface VFilterSequenceExpression <: Expression {
    type: "VFilterSequenceExpression"
    expression: Expression
    filters: [ VFilter ]

interface VFilter <: Node {
    type: "VFilter"
    callee: Identifier
    arguments: [ Expression ]
  • This is mustaches or directive values.
  • If syntax errors exist, VExpressionContainer#expression is null.
  • If it's an empty mustache, VExpressionContainer#expression is null. (e.g., {{ /* a comment */ }})
  • Reference is objects but not Node. Those are external references which are in the expression.
  • Reference#variable is the variable which is defined by a VElement. If a reference uses a global variable or a member of VM, this is null.
  • VForExpression is an expression node like ForInStatement but it has an array as left property and does not have body property. This is the value of v-for directives.
  • VOnExpression is an expression node like BlockStatement but it does not have braces. This is the value of v-on directives only if the v-on directive doesn't have that argument.
  • VSlotScopeExpression is an expression node like VariableDeclarator. This is the value of v-slot directives, slot-scope attributes, and scope attributes.
  • VFilterSequenceExpression is an expression node for Vue.js Filters syntax.

Note: vue-eslint-parser transforms v-for="(x, i) in list" to for(let [x, i] in list); then gives the configured parser (espree by default) it. This implies that it needs the capability to parse ES2015 destructuring in order to parse v-for directives.


interface VDirectiveKey <: Node {
    type: "VDirectiveKey"
    name: VIdentifier
    argument: VExpressionContainer | VIdentifier | null
    modifiers: [ VIdentifier ]
  • The name property doesn't have v- prefix. It's dropped.
  • The argument property is a VExpressionContainer node if it's a dynamic argument.
  • In the shorthand of v-bind case, the property is "bind" and the name.rawName property is ":".
  • In the shorthand of v-bind with .prop modifier case, the property is "bind" and the name.rawName property is "." and the modifiers property includes a VIdentifier node of "prop".
  • In the shorthand of v-on case, the property is "on" and the name.rawName property is @.
  • In the shorthand of v-slot case, the property is "slot" and the name.rawName property is #.
  • Otherwise, shorthand property is always false.


interface VLiteral <: Node {
    type: "VAttributeValue"
    value: string
  • This is similar to Literal nodes but this is not always quoted.
  • HTML entities in the value property are decoded.


interface VAttribute <: Node {
    type: "VAttribute"
    directive: false
    key: VIdentifier
    value: VLiteral | null

interface VDirective <: Node {
    type: "VAttribute"
    directive: true
    key: VDirectiveKey
    value: VExpressionContainer | null
  • If their attribute value does not exist, the value property is null.
  • The slot-scope attribute becomes directive:true specially.


interface VStartTag <: Node {
    type: "VStartTag"
    attributes: [ VAttribute ]


interface VEndTag <: Node {
    type: "VEndTag"


interface VElement <: Node {
    type: "VElement"
    namespace: string
    name: string
    startTag: VStartTag
    children: [ VText | VExpressionContainer | VElement ]
    endTag: VEndTag | null
    variables: [ Variable ]

interface Variable {
    id: Identifier
    kind: "v-for" | "scope"
    references: [ Reference ]
  • Variable is objects but not Node. Those are variable declarations that child elements can use. The elements which have v-for directives or a special attribute scope can declare variables.
  • Variable#references is an array of references which use this variable.


interface VRootElement <: VElement {
    tokens: [ Token ]
    comments: [ Token ]
    errors: [ ParseError ]

interface Token <: Node {
    type: string
    value: string

interface ParseError <: Error {
    code?: string
    message: string
    index: number
    lineNumber: number
    column: number


extend interface Program {
    templateBody: VRootElement | null

This spec enhances Program nodes as it has the root node of <template>. This supports only HTML for now. However, I'm going to add other languages Vue.js supports. The AST of other languages may be different form to VElement.