🌊 Merval

The world's first zero-dependency Mermaid diagram validator. Instant syntax validation without CLI calls or heavy dependencies.

🎯 Why Merval?

Tired of installing @mermaid-js/mermaid-cli and its 400+ dependencies (Puppeteer, Chromium, etc.) just to validate a simple diagram? Merval gives you instant Mermaid syntax validation with zero dependencies.

• ⚡ Instant: No CLI calls, no external processes
• 🪶 Zero Dependencies: Pure JavaScript, no Puppeteer, no Chromium
• 🎯 100% Compatible: Tested against Mermaid CLI v11.12.0
• 🚀 Lightning Fast: Direct parsing, no rendering overhead
• 🛡️ Type Safe: Built with TypeScript for robust validation

Supported Diagram Types

• Flowchart (graph/flowchart)
• Sequence Diagram
• Class Diagram
• State Diagram
• Entity Relationship Diagram
• User Journey
• Gantt Chart
• Pie Chart
• Gitgraph
• Mindmap
• Timeline
• xychart-beta (bar/line charts)
• block-beta (block diagrams)

📦 Installation

# Using npm
npm install @aj-archipelago/merval

# Using yarn  
yarn add @aj-archipelago/merval

# Using pnpm
pnpm add @aj-archipelago/merval

🚀 Quick Start

import { validateMermaid } from '@aj-archipelago/merval';

// Instant validation - no CLI, no dependencies!
const result = validateMermaid(`
graph TD
    A[Start] --> B{Decision}
    B -->|Yes| C[Process A]
    B -->|No| D[Process B]
    C --> E[End]
    D --> E[End]
`);

console.log(result.isValid); // true/false
console.log(result.diagramType); // 'flowchart'
console.log(result.errors); // [] or array of error objects

Mermaid Version Compatibility

This validator is tested against Mermaid CLI v11.12.0 to ensure 100% compatibility. The library tracks which version it was validated against and can warn about potential compatibility issues.

Version Information

import { getMermaidVersionInfo, isMermaidVersionSupported } from '@aj-archipelago/merval';

// Get version compatibility info
const versionInfo = getMermaidVersionInfo();
console.log(versionInfo);
// {
//   validatedAgainst: "11.12.0",
//   lastValidated: "2024-10-15", 
//   cliVersion: "@mermaid-js/mermaid-cli@11.12.0"
// }

// Check if a specific version is supported
console.log(isMermaidVersionSupported("11.12.0")); // true
console.log(isMermaidVersionSupported("12.0.0"));   // false

Version-Aware Validation

import { validateMermaid } from '@aj-archipelago/merval';

// Basic validation (no version check)
const result = validateMermaid(mermaidCode);

// Validate with version compatibility check
const result = validateMermaid(mermaidCode, "12.0.0");
if (!result.isValid && result.errors.some(e => e.code === 'VERSION_MISMATCH')) {
  console.log('Warning: This validator was not tested against Mermaid 12.0.0');
}

Updating Mermaid Version Compatibility

When updating this validator to work with a new Mermaid version, use the provided script:

# Update to a new Mermaid version
npm run update-version 12.0.0 2024-11-01

# Or manually run the script
node scripts/update-version.js 12.0.0 2024-11-01

This script will:

1. Update package.json with the new version info
2. Update src/version.ts with the new version constants
3. Build the project
4. Run all tests
5. Provide next steps for full compatibility testing

API

import { validateMermaid, isValidMermaid, getDiagramType } from '@aj-archipelago/merval';

// Basic validation
const result = validateMermaid(`
graph TD
    A[Start] --> B{Decision}
    B -->|Yes| C[Process A]
    B -->|No| D[Process B]
    C --> E[End]
    D --> E[End]
`);

console.log(result.isValid); // true/false
console.log(result.diagramType); // 'flowchart'
console.log(result.errors); // [] or array of error objects

// Simple boolean validation
const isValid = isValidMermaid(mermaidCode); // true/false

// Get diagram type only
const diagramType = getDiagramType(mermaidCode); // 'flowchart', 'sequence', etc.

// Validation with version compatibility check
const result = validateMermaid(mermaidCode, "12.0.0");
if (!result.isValid && result.errors.some(e => e.code === 'VERSION_MISMATCH')) {
  console.log('Version compatibility warning');
}

Error Format

{
  isValid: false,
  diagramType: 'flowchart',
  errors: [
    {
      line: 2,
      column: 15,
      message: "Missing arrow between nodes",
      code: "MISSING_ARROW",
      suggestion: "Add '-->' to connect nodes"
    }
  ]
}

💡 Why Merval?

The Problem with Traditional Mermaid Validation

# Traditional approach - heavy dependencies
npm install @mermaid-js/mermaid-cli
# Installs 400+ packages including:
# - puppeteer (Chromium browser)
# - canvas, cairo, pango, etc.
# - Native dependencies requiring compilation

The Merval Solution

# Merval - zero dependencies
npm install merval
# Installs only merval - that's it!

Merval gives you the same validation accuracy as Mermaid CLI but with:

• Zero dependencies - no Puppeteer, no Chromium, no native compilation
• Instant validation - no CLI process spawning, no file I/O
• Same accuracy - 100% compatible with Mermaid CLI v11.12.0
• TypeScript support - full type safety out of the box

Implementation Strategy

1. Lexical Analysis: Tokenize input into meaningful components
2. Syntax Analysis: Build AST and validate structure
3. Semantic Validation: Check relationships and references
4. Diagram-Specific Rules: Each type has unique validation

Architecture

src/
├── lexer.js          # Tokenize input
├── parser.js         # Parse tokens into AST
├── validators/
│   ├── flowchart.js  # Flowchart-specific validation
│   ├── sequence.js   # Sequence diagram validation
│   ├── xychart.js    # xychart-beta validation
│   └── ...
├── ast/              # AST node definitions
└── index.js          # Main API

License

MIT - Compatible with Mermaid.js MIT license

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Built with 💖 by diagram enthusiasts for diagram enthusiasts.