SNOMED CT ECL Formatter

A Visual Studio Code extension that provides syntax highlighting and document formatting for SNOMED CT Expression Constraint Language (ECL).

Features

• Syntax Highlighting: Full TextMate grammar for ECL syntax
• Document Formatting: Intelligent formatting with complexity-aware line breaking
• Range Formatting: Format selected text regions
• Idempotent: Formatting the same text multiple times produces identical results

Web Formatter

Try the online ECL formatter: https://mattcordell.github.io/ecl-formatter/

Format ECL expressions directly in your browser without installing the extension. The web version uses the same formatting logic as the VS Code extension, ensuring consistent results.

Features:

• Format ECL expressions online
• Copy formatted output to clipboard
• Example expressions included
• Mobile-friendly responsive design
• Works in all modern browsers

Installation

From VSIX

1. Download the .vsix file from releases
2. In VS Code: Extensions → ... → Install from VSIX
3. Select the downloaded file

From Source

git clone https://github.com/MattCordell/ecl-formatter.git
cd ecl-formatter
npm install
npm run build

Press F5 to launch Extension Development Host for testing.

Usage

File Extensions

The extension activates for files with extensions:

• .ecl
• .snomed-ecl

Format Document

• Command: Format Document
• Keyboard: Shift+Alt+F (Windows/Linux) or Shift+Option+F (macOS)
• Command Palette: "Format Document"

Format Selection

• Select text
• Command: Format Selection
• Command Palette: "Format Selection"

Configuration

{
  "ecl.formatter.indentSize": 2  // Number of spaces per indent level
}

ECL Syntax Overview

SNOMED CT Expression Constraint Language (ECL) is a formal language for defining constraints on SNOMED CT concepts.

Examples:

// Simple concept reference
404684003 |Clinical finding|

// Descendant constraint
<< 404684003

// Refinement
<< 404684003: 363698007 = << 39057004

// Compound expression
<< 404684003 AND << 987654321

// With filters
<< 404684003 {{ term = "heart" }}

// Reverse attribute (brief syntax)
< 91723000 : R 363698007 = < 125605004

// Reverse attribute (long syntax)
< 91723000 : reverseOf 363698007 = < 125605004

// Dotted attribute
< 125605004 . 363698007

// Chained dotted attributes
<< 19829001 . < 47429007 . 363698007

Architecture

• src/extension.ts - VS Code extension entry point
• src/parser/ - Chevrotain-based lexer and parser
  • lexer.ts - Token definitions
  • parser.ts - Grammar rules (CST)
  • ast.ts - AST node type definitions
  • visitor.ts - CST to AST transformation
• src/formatter/ - Document formatting
  • format.ts - Pure formatting function
  • formatter.ts - VS Code providers
  • printer.ts - AST to formatted text
  • rules.ts - Formatting logic and complexity detection
• syntaxes/ - TextMate grammar for syntax highlighting
• src/test/ - Test suite (vitest)

Contributing

Please read CONTRIBUTING.md for details on our documentation standards, code style, and development process.

Resources

• ECL Specification
• ECL ANTLR Grammar
• SNOMED International

License

[License information to be added]

Acknowledgments

Built with Chevrotain parser framework.