@lanexio/parser-grammar-xml

This page documents @lanexio/parser-grammar-xml, the XML grammar package implementing XML 1.0 5th Edition with optional DTD validation, external entity resolution, and comprehensive attribute-level DTD information.

• Version: Stable
• Module name: parser-grammar-xml
• Package: @lanexio/parser-grammar-xml
• Import path: @lanexio/parser-grammar-xml
• Layer: 2 (Grammar)
• Runtime: Universal
• Module format: ESM
• Stability: Stable
• Primary use case: Parse XML documents into a flat AST with optional DTD validation.

Layer contract

Layer 2 dependency rules

This package depends only on Layer 1 core packages. It does not import from query, bridge, devtools, or entry packages. Grammar packs never depend on other grammar packs.

When to use this module

• You need to parse XML 1.0 documents into a traversable AST.
• You need optional DTD validation (content models, required attributes, ID/IDREF consistency).
• You need to resolve external DTD subsets via a callback.
• You need access to parsed DTD declarations (element, attribute-list, entity).

Module boundary

Boundary	Description
Inputs	Uint8Array (source bytes) + optional ParseXmlOptions
Outputs	LexTree (flat AST)
Side effects	None (the parser does no I/O; external DTD resolved via callback)
Determinism	Yes
External dependencies	@lanexio/parser-core
Never-throw guarantee	Yes
Security surface	None (parse only, no output generation; no entity expansion)

Installation

1. Install the package.

   pnpm

   pnpm add @lanexio/parser-grammar-xml

   npm

   npm install @lanexio/parser-grammar-xml

   yarn

   yarn add @lanexio/parser-grammar-xml

2. Import the named export.

   import { parseXml } from '@lanexio/parser-grammar-xml';

Peer dependencies

Requirement	Required	Layer	Notes
@lanexio/parser-core	Yes	1	^1.0.0

Basic Usage

import { parseXml } from '@lanexio/parser-grammar-xml';

const encoder = new TextEncoder();
const bytes = encoder.encode('<root><item id="1">value</item></root>');

const tree = parseXml(bytes);

console.log(tree.nodeCount);

DTD validation

import { parseXml } from '@lanexio/parser-grammar-xml';

const encoder = new TextEncoder();
const tree = parseXml(
  encoder.encode('<!DOCTYPE root [ <!ELEMENT root (#PCDATA)> ]><root>text</root>'),
  { validate: true }
);

Exports

Export	Type	Description
parseXml	(bytes: Uint8Array, options?: ParseXmlOptions) => LexTree	Parse XML. Never throws.
XmlKind	const object	Numeric kind IDs for all XML node types.
XmlField	const object	Numeric field IDs for XML element slots.
XML_FIELD_NAMES_BY_ID	readonly string[]	Field name lookup by numeric field ID.
XML_KIND_NAMES_BY_ID	readonly Record<number, string>	Kind-name lookup by numeric ID.
xmlGrammar	LanexioParserPureGrammar	Grammar descriptor for use with parser-pure.
xmlRegistration	GrammarRegistration	Registration for the unified grammar registry.
xmlReuseOracle	ReuseOracle	Incremental reuse oracle.

Options

ParseXmlOptions

Field	Type	Required	Default	Description
validate	boolean	No	false	When true, validates against the DTD after parsing.
resolveExternal	ExternalResolver	No	undefined	Callback for resolving external DTD subset references. The parser does no I/O.
baseUri	string	No	""	Base URI for resolving relative SYSTEM identifiers.

Return shape

Property	Type	Description
root	LexNode	Root node of the XML document.
nodeCount	number	Total nodes in the tree.
source	Uint8Array	Original parsed bytes.

Exported types

Type	Purpose	Notes
ParseXmlOptions	Options for parseXml	See options table above.
ExternalResolver	Callback for resolving external DTD subsets	(publicId, systemId, baseUri) => Uint8Array | null
DtdInfo	Parsed DTD declarations	Elements, attlists, entities
DtdElementDecl	DTD element declaration	Name and content model
DtdAttlistDecl	DTD attribute-list declaration	Element name and attr defs
DtdAttrDef	Single attribute definition in ATTLIST	Name, type, default
DtdEntityDecl	DTD entity declaration	Name and value
XmlKindType	Union of all XmlKind values	Type-safe kind reference
XmlFieldType	Union of all XmlField values	Type-safe field reference

Configuration and Extension

DTD resolution

The resolveExternal callback allows callers to provide external DTD content without the parser performing network I/O. The parser’s no-expand security model prevents billion-laughs attacks.

Accessibility

Accessibility requirements

• No direct accessibility surface. The XML parser produces flat AST data structures.

Accessibility checklist

Concern	Status
Generated output semantics	Not applicable (data format)
ARIA attributes in serialized output	Not applicable
Semantic element round-trip	Not applicable

Security

Security considerations

• parseXml never throws on any byte sequence.
• The parser uses a no-expand security model for entities (billion-laughs guarantee).

Threat	Mitigation	Status
Malformed input byte sequence	Panic-free guarantee: all inputs accepted, errors produce LexError AST nodes	Implemented
Billion-laughs (entity expansion)	No entity expansion: entities are tracked but not substituted in parsed output	Implemented

Companion packages

Package	Relationship	Layer	Notes
@lanexio/parser-core	Requires	1	Provides LexTree, LexNode, LexCursor
@lanexio/parser	Consumes	6	Unified entry point

Changelog

Version	Date	Status	Notable changes
1.0.0	2026-05-29	Current	Initial stable release. Apache-2.0.

Migration notes

• None.

Related Content

Flat AST How the 16-byte node layout works.

Stability Guarantees Never-throw, panic-free, and 3-token recovery.