XML Engine

A lightning-fast, zero-dependency, modular XML parsing, XPath generation, and indexing engine designed specifically for VS Code. Provides intelligent element indexing, XPath generation (absolute and child-predicate modes), and an XPath search engine.

Overview

The XML Engine is a complete rewrite and consolidation of legacy XML extensions (xml-xpath, xml-element-indexer) into a single cohesive, high-performance architecture. By ditching slow DOM-based parsers in favor of a custom Regex-based token streaming engine, this extension operates instantly on massive XML documents without locking up the VS Code UI.

Requirements

• VS Code 1.74+
• Node.js 18+

Installation

1. Clone or copy this extension to your local machine
2. Open the folder in VS Code
3. Press F5 to launch the extension in debug mode

Or package as a VSIX:

npm install -g @vscode/vsce
vsce package

Features

• Blazing Fast Tokenizer: Custom regex-based XML token stream parser that extracts tags, attributes, and text content while preserving byte-offsets. Skips CDATA and Comments automatically.
• Intelligent Indexing:
  • Parent-Scoped Sibling Indexing: Standard XPath indexing where elements are numbered relative to their identical siblings under the same parent.
  • Global Depth Indexing: Numbers elements based on their global depth position in the tree.
  • Attribute-Based Partitioning: Numbers elements relative to a configured partitioning attribute (e.g., [@id='foo'][1]).
• Robust XPath Generation:
  • Absolute XPath: Generates precise positional paths like /catalog[1]/book[2]/title[1].
  • Successor-Predicate XPath: Generates smart, human-readable descendant paths using landmark attributes or identifying children (e.g., //book[@id='b1']//title).
  • Child-Predicate XPath: Uses child elements as predicates for precise identification (e.g., //book[title='Clean Code']/author).
• XPath Search Engine: A fully custom, dependency-free XPath 1.0 subset evaluator that executes lightning-fast searches against the token stream.
• VS Code Presentation Layer:
  • Live UI Badges: Injects [1], [2] inline text editor decorations using window.createTextEditorDecorationType.
  • Status Bar: Displays the XPath of the element currently under the cursor.
  • Tree View: A sidebar explorer showing the XML structure combined with the engine's indices.
  • Hover Provider: Markdown popups on tag hover displaying the XPath and a direct "Copy" action.
  • CodeLens: Injects inline "Copy XPath" actions above important tags or virtual roots.
  • Search QuickPick: A live search interface to query and navigate to XPath matches.

Usage

Basic Usage

1. Open any XML file in VS Code
2. The extension automatically indexes elements
3. Element indices appear inline (e.g., [1], [2])
4. The status bar shows the XPath at cursor position

Commands

Indexing Modes

• full: Index all elements in the document
• cursor: Index elements around the cursor only
• inline: Index elements as you type
• range: Index elements within a configurable range

XPath Generation Strategies

Absolute (default):

/catalog[1]/book[2]/title[1]

Child-Predicate:

//book[title='Clean Code'][author='Robert Martin']/isbn

Configuration

The extension is highly configurable via standard VS Code settings (settings.json):

General Settings

XPath Generation

Indexing Options

Visual Options

Performance

Example Configuration

{
  "xmlEngine.enabled": true,
  "xmlEngine.mode": "cursor",
  "xmlEngine.xpathGenerationStrategy": "child-predicate",
  "xmlEngine.preferredAttributes": ["id", "type", "name", "key"],
  "xmlEngine.childPredicateIdentifyingChildren": ["title", "name", "label", "id", "key", "value"],
  "xmlEngine.indexColor": "#7ec699",
  "xmlEngine.enableCache": true,
  "xmlEngine.cacheSize": 100
}

Architecture

src/
├── engine/           # Core XML logic (headless)
│   ├── tokenizer.js      # Regex-based XML parser
│   ├── indexer.js      # Element indexing
│   ├── path/           # XPath generation
│   │   ├── absolute.js
│   │   └── child-predicate.js
│   └── search/         # XPath evaluator
├── vscode/         # VS Code integration
│   ├── extension.js     # Entry point
│   ├── config-manager.js
│   ├── decoration-manager.js
│   ├── status-bar.js
│   ├── tree-view.js
│   ├── hover-provider.js
│   ├── search-ui.js
│   └── copy-lens.js
└── shared/         # Common utilities
    ├── constants.js
    ├── logger.js
    └── debug.js

Development

Install dependencies:

npm install

Run tests:

npm run test

Run integration tests:

npm run test:integration

Debug the extension:

1. Press F5 in VS Code to launch extension host
2. Open an XML file to test

Keybindings

All keybindings require the editor to be an XML language file (xml, xsl, xsd, wsdl, xaml, svg, xhtml):

Language Support

The extension activates for these languages:

• XML (.xml)
• XSL (.xsl, .xslt)
• XSD (.xsd)
• WSDL (.wsdl)
• XAML (.xaml)
• SVG (.svg)
• XHTML (.xhtml)

License

MIT