# AST for YAML

See details: [../src/ast.ts](../src/ast.ts)

## Node

```ts
interface Node {
    type: string;
    loc: SourceLocation;
    range: [number, number];
}
```

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

## Content Nodes

### YAMLMapping

```ts
interface YAMLMapping extends Node {
    type: "YAMLMapping"
    style: "block" | "flow"
    pairs: YAMLPair[]
    parent: YAMLDocument | YAMLPair | YAMLSequence | YAMLWithMeta
}
```

This is mappings.

- `style` ... If `"block"`, it is [block style mapping]. If `"flow"`, it is [flow style mapping]. e.g. `{ foo: bar }`
- `pairs` ... An array of `key: value` pairs.

### YAMLPair

```ts
interface YAMLPair extends Node {
    type: "YAMLPair"
    key: YAMLMapping | YAMLSequence | YAMLScalar | YAMLAlias | YAMLWithMeta | null
    value: YAMLMapping | YAMLSequence | YAMLScalar | YAMLAlias | YAMLWithMeta | null
    parent: YAMLMapping
}
```

This is `key: value` pairs.

### YAMLSequence

```ts
interface YAMLSequence extends Node {
    type: "YAMLSequence"
    style: "block" | "flow"
    entries: (YAMLMapping | YAMLSequence | YAMLScalar | YAMLAlias | YAMLWithMeta)[]
    parent: YAMLDocument | YAMLPair | YAMLSequence | YAMLWithMeta
}
```

This is sequences.

- `style` ... If `"block"`, it is [block style sequence]. If `"flow"`, it is [flow style sequence]. e.g. `{ foo: bar }`
- `entries` ... An array of sequence entries.

### YAMLScalar

```ts
interface YAMLScalar extends Node {
    type: "YAMLScalar"
    style: "plain" | "double-quoted" | "single-quoted" | "literal" | "folded"
    value: string | number | boolean | null
    parent: YAMLDocument | YAMLPair | YAMLSequence | YAMLWithMeta
}
```

This is scalars.

#### YAMLPlainScalar

```ts
interface YAMLPlainScalar extends YAMLScalar {
    style: "plain"
    strValue: string
    raw: string
}
```

This is [plain style scalars] (unquoted scalars).

#### YAMLDoubleQuotedScalar

```ts
interface YAMLDoubleQuotedScalar extends YAMLScalar {
    style: "double-quoted"
    strValue: string
    value: string
    raw: string
}
```

This is [double-quoted style scalars].

#### YAMLSingleQuotedScalar

```ts
interface YAMLSingleQuotedScalar extends YAMLScalar {
    style: "single-quoted"
    strValue: string
    value: string
    raw: string
}
```

This is [single-quoted style scalars].

#### YAMLBlockLiteralScalar

```ts
interface YAMLBlockLiteralScalar extends YAMLScalar {
    style: "literal"
    chomping: "clip" | "keep" | "strip"
    indent: null | number
    value: string
}
```

This is [literal style scalars].

e.g.

```yaml
|
foo
bar
```

- `chomping`
  - `"clip"` ... The chomping indicator is not specified.
  - `"strip"` ... The `-` chomping indicator is specified.
  - `"keep"` ... The `+` chomping indicator is specified.
- `indent` ... The specified indentation indicator. It is null if not specified.

#### YAMLBlockFoldedScalar

```ts
interface YAMLBlockFoldedScalar extends YAMLScalar {
    style: "folded"
    chomping: "clip" | "keep" | "strip"
    indent: null | number
    value: string
}
```

This is [folded style scalars].

e.g.

```yaml
>
foo
bar
```

### YAMLAlias

```ts
interface YAMLAlias extends Node {
    type: "YAMLAlias"
    name: string
    parent: YAMLDocument | YAMLPair | YAMLSequence | YAMLWithMeta
}
```

This is [aliases].

## Tag and Anchor

### YAMLWithMeta

```ts
interface YAMLWithMeta extends Node {
    type: "YAMLWithMeta"
    anchor: YAMLAnchor | null
    tag: YAMLTag | null
    value: YAMLMapping | YAMLSequence | YAMLScalar | YAMLAlias | null
    parent: YAMLDocument | YAMLPair | YAMLSequence
}
```

If it has a tag or anchor, the content node will be wrapped in this node.

### YAMLAnchor

```ts
interface YAMLAnchor extends Node {
    type: "YAMLAnchor"
    name: string
    parent: YAMLWithMeta
}
```

### YAMLTag

```ts
interface YAMLTag extends Node {
    type: "YAMLTag"
    tag: string
    parent: YAMLWithMeta
}
```

## Document

### YAMLDocument

```ts
interface YAMLDocument extends Node {
    type: "YAMLDocument"
    directives: YAMLDirective[]
    content: YAMLMapping | YAMLSequence | YAMLScalar | YAMLAlias | YAMLWithMeta | null
    parent: YAMLProgram
    anchors: { [key: string]: YAMLAnchor[] }
    // YAML version
    version: string
}
```

### YAMLDirective

```ts
interface YAMLDirective extends Node {
    type: "YAMLDirective"
    value: string
    parent: YAMLDocument
}
```

This is directives. In the following example, `%YAML 1.2` is represented by this node.

```yaml
%YAML 1.2
---
"foo"
```

### Program

```js
extend interface Program {
    body: YAMLDocument[]
}
```

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

[ESLint - The AST specification]: https://eslint.org/docs/developer-guide/working-with-custom-parsers#the-ast-specification
[block style mapping]: https://yaml.org/spec/1.2/spec.html#id2798057
[flow style mapping]: https://yaml.org/spec/1.2/spec.html#id2790832
[block style sequence]: https://yaml.org/spec/1.2/spec.html#id2797382
[flow style sequence]: https://yaml.org/spec/1.2/spec.html#id2790320
[plain style scalars]: https://yaml.org/spec/1.2/spec.html#id2788859
[double-quoted style scalars]: https://yaml.org/spec/1.2/spec.html#id2787109
[single-quoted style scalars]: https://yaml.org/spec/1.2/spec.html#id2788097
[literal style scalars]: https://yaml.org/spec/1.2/spec.html#id2795688
[folded style scalars]: https://yaml.org/spec/1.2/spec.html#id2796251
[aliases]: https://yaml.org/spec/1.2/spec.html#id2786196