AST for TOML

February 24, 2026 ยท View on GitHub

See details: ../src/ast/ast.ts

You can see the AST on the Online DEMO.

Node

interface BaseTOMLNode {
    type: string;
    loc: SourceLocation;
    range: [number, number];
}

All nodes have type, range, loc and parent properties according to ESLint - The AST specification.

Content Nodes

TOMLValue

type TOMLValue = TOMLStringValue | TOMLNumberValue | TOMLBooleanValue | TOMLDateTimeValue

// When expanded, it has the same definition as the following.
interface TOMLValue extends BaseTOMLNode {
    type: "TOMLValue"
    kind: "string" | "integer" | "float" | "boolean" | "offset-date-time" | "local-date-time" | "local-date" | "local-time"
    value: string | number | boolean | Date
    parent: TOMLKey | TOMLKeyValue | TOMLArray
}

This is value.

  • kind ... The kind of value. Each kind has more detailed properties.
  • value ... A value.

TOMLStringValue

interface TOMLStringValue extends BaseTOMLNode {
    type: "TOMLValue"
    kind: "string"
    value: string
    style: "basic" | "literal"
    multiline: boolean
    parent: TOMLKeyValue | TOMLArray
}

This is String value.

e.g.

str1 = "Basic strings"
str2 = """
Multi-line
Basic strings"""
str3 = 'Literal strings'
str4 = '''
Multi-line
Literal strings'''
  • style ... If "basic", the value was defined as (multi-line) basic string. If "literal", the value was defined as (multi-line) literal string.
  • multiline ... If true, the value was defined as multi-line basic string or multi-line literal string.

TOMLIntegerValue

interface TOMLIntegerValue extends BaseTOMLNode {
    type: "TOMLValue"
    kind: "integer"
    value: number
    bigint: bigint
    number: string
    parent: TOMLKeyValue | TOMLArray
}

This is Integer value.

e.g.

int = 42
  • value ... The integer value defined by TOML. However, it can overflow.
  • bigint ... The integer value defined by TOML is stored as BigInt.
  • number ... The integer expressed as a string.

TOMLFloatValue

interface TOMLFloatValue extends BaseTOMLNode {
    type: "TOMLValue"
    kind: "float"
    value: number
    number: string
    parent: TOMLKeyValue | TOMLArray
}

This is Float value.

e.g.

float = 3.14
nan = nan
infinity = inf
  • value ... The float value defined by TOML. The float contains NaN and Infinity.
  • number ... The float expressed as a string.

TOMLBooleanValue

interface TOMLBooleanValue extends BaseTOMLNode {
    type: "TOMLValue"
    kind: "boolean"
    value: boolean
    parent: TOMLKeyValue | TOMLArray
}

This is Boolean.

e.g.

bool1 = true
bool2 = false

TOMLDateTimeValue

interface TOMLDateTimeValue extends BaseTOMLNode {
    type: "TOMLValue"
    kind: "offset-date-time" | "local-date-time" | "local-date" | "local-time"
    value: Date
    datetime: string
    parent: TOMLKeyValue | TOMLArray
}

This is Offset Date-Time or Local Date-Time or Local Date or Local Time value.

e.g.

odt = 1979-05-27T07:32:00Z
ldt = 1979-05-27T07:32:00
ld = 1979-05-27
lt = 07:32:00
  • kind ... If "offset-date-time", the value was defined as offset date-time. If "local-date-time", the value was defined as local date-time. If "local-date", the value was defined as local date. If "local-time", the value was defined as local time.
  • value ... The date is stored, but it may have been truncated to a value that can be represented by JavaScript.
  • datetime ... The date expressed as a string.

TOMLArray

interface TOMLArray extends BaseTOMLNode {
    type: "TOMLArray"
    elements: (TOMLValue | TOMLArray | TOMLInlineTable)[]
    parent: TOMLKeyValue | TOMLArray
}

This is Array.

e.g.

array = [ 1, 2, 3]

TOMLInlineTable

interface TOMLInlineTable extends BaseTOMLNode {
    type: "TOMLInlineTable"
    body: TOMLKeyValue[]
    parent: TOMLKeyValue | TOMLArray
}

This is Inline Table.

e.g.

name = { first = "Tom", last = "Preston-Werner" }

Key/Value Pair

TOMLKeyValue

interface TOMLKeyValue extends BaseTOMLNode {
    type: "TOMLKeyValue"
    key: TOMLKey
    value: TOMLValue | TOMLArray | TOMLInlineTable
    parent: TOMLTopLevelTable | TOMLTable | TOMLInlineTable
}

This is Key/Value Pair.

e.g.

key = "value"

TOMLKey

interface TOMLKey extends BaseTOMLNode {
    type: "TOMLKey"
    keys: (TOMLBare | TOMLStringKey)[]
    parent: TOMLKeyValue | TOMLTable
}

This is Key.

e.g.

physical.color = "orange"

TOMLBare

interface TOMLBare extends BaseTOMLNode {
    type: "TOMLBare"
    name: string
    parent: TOMLKey
}

This is Bare key.

e.g.

bare-key = 42

TOMLQuoted

interface TOMLQuoted extends BaseTOMLNode {
    type: "TOMLQuoted"
    value: string
    style: "basic" | "literal"
    parent: TOMLKey
}

This is Quoted key.

e.g.

"Key1" = 42
'Key2' = 42

Table

TOMLTable

interface TOMLTable extends BaseTOMLNode {
    type: "TOMLTable"
    kind: "standard" | "array"
    key: TOMLKey
    resolvedKey: (string | number)[]
    body: TOMLKeyValue[]
    parent: TOMLTopLevelTable
}

This is Table or Array of Table.

e.g.

[table]
key1 = "some string"

[[array.of.table]]
name = "Hammer"
sku = 738594937

[[array.of.table]]
name = "Nail"
sku = 284758393
  • kind ... If "standard", the table was defined as []. If "array", the table was defined as [[]].
  • resolvedKey ... An array of keys that are actually applied. In the above example, the first [[array.of.table]] is resolved as ["array", "of", "table", 0], the second [[array.of.table]] is resolved as ["array", "of", "table", 1].

Document

TOMLTopLevelTable

interface TOMLTopLevelTable extends BaseTOMLNode {
    type: "TOMLTopLevelTable"
    body: (TOMLKeyValue | TOMLTable)[]
    parent: TOMLProgram
}

Program

interface TOMLProgram extends BaseTOMLNode {
    type: "Program"
    body: [TOMLTopLevelTable]
    sourceType: "module"
    comments: Comment[]
    tokens: Token[]
    parent: null
}

The body of the Program node generated by this parser is an array of TOMLTopLevelTable.