render-template

Render templates with variable substitution, supporting various syntax formats and helper functions.

When to Use

• Format commit messages with dynamic data
• Generate report sections with variables
• Create formatted outputs from templates
• Replace placeholders in text templates
• Consolidate formatting logic across Skills

Instructions

Step 1: Receive Template and Data

Accept template string and variable data.

Expected Input:

• template: String (template with placeholders)
• variables: Object (key-value pairs for substitution)
• syntax: String (optional: mustache|shell|mixed, default: mustache)

Supported Syntax:

• Mustache: {{variable}}, {{object.property}}
• Shell: ${variable}, ${VARIABLE}
• Mixed: Supports both

Step 2: Parse Template

Identify all placeholders in template.

Placeholder Patterns:

• {{variable}}: Simple variable
• {{object.property}}: Nested property
• {{#if condition}}...{{/if}}: Conditional (optional)
• {{#each array}}...{{/each}}: Loop (optional)

Step 3: Resolve Variables

Replace placeholders with values from variables object.

Resolution Rules:

• Direct match: {{name}} → variables.name
• Nested property: {{user.name}} → variables.user.name
• Missing variable: Replace with empty string or keep placeholder (configurable)
• Undefined: Replace with empty string

Step 4: Apply Filters (Optional)

Support simple filters if specified.

Common Filters:

• {{variable | uppercase}}: Convert to uppercase
• {{variable | lowercase}}: Convert to lowercase
• {{variable | capitalize}}: Capitalize first letter
• {{date | format:YYYY-MM-DD}}: Format date

Step 5: Return Rendered Output

Return final rendered string.

Expected Output: String (template with variables replaced)

Error Handling

• Missing Variables: Replace with empty string or warn (configurable)
• Invalid Template Syntax: Return error describing syntax issue
• Circular References: Detect and return error
• Type Mismatch: Convert to string automatically

Examples

Example 1: Simple Variable Substitution

Input:

{
  "template": "Hello {{name}}, your score is {{score}}!",
  "variables": {
    "name": "Alice",
    "score": 95
  },
  "syntax": "mustache"
}

Output:

Hello Alice, your score is 95!

Example 2: Nested Properties

Input:

{
  "template": "User: {{user.name}} ({{user.email}})\nRole: {{user.role}}",
  "variables": {
    "user": {
      "name": "Bob",
      "email": "bob@example.com",
      "role": "admin"
    }
  }
}

Output:

User: Bob (bob@example.com)
Role: admin

Example 3: Shell Syntax

Input:

{
  "template": "Version: ${VERSION}\nDate: ${RELEASE_DATE}",
  "variables": {
    "VERSION": "0.8.0",
    "RELEASE_DATE": "2025-10-17"
  },
  "syntax": "shell"
}

Output:

Version: 0.8.0
Date: 2025-10-17

Example 4: Commit Message Template

Input:

{
  "template": "{{type}}({{scope}}): {{description}}\n\n{{body}}\n\n🤖 Generated with Claude Code\nCo-Authored-By: Claude <noreply@anthropic.com>",
  "variables": {
    "type": "feat",
    "scope": "auth",
    "description": "add OAuth2 support",
    "body": "Implemented OAuth2 flow with token refresh.\nSupports Google and GitHub providers."
  }
}

Output:

feat(auth): add OAuth2 support

Implemented OAuth2 flow with token refresh.
Supports Google and GitHub providers.

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>

Example 5: Missing Variables

Input:

{
  "template": "Name: {{name}}\nAge: {{age}}\nCity: {{city}}",
  "variables": {
    "name": "Alice"
  }
}

Output (with empty string replacement):

Name: Alice
Age:
City:

Output (with keep placeholder):

Name: Alice
Age: {{age}}
City: {{city}}

Example 6: Report Header Template

Input:

{
  "template": "# {{reportType}} Report: {{version}}\n\n**Generated**: {{timestamp}}\n**Status**: {{statusEmoji}} {{status}}\n**Version**: {{version}}",
  "variables": {
    "reportType": "Bug Hunting",
    "version": "2025-10-17",
    "timestamp": "2025-10-17 14:30:00 UTC",
    "statusEmoji": "✅",
    "status": "success"
  }
}

Output:

# Bug Hunting Report: 2025-10-17

**Generated**: 2025-10-17 14:30:00 UTC
**Status**: ✅ success
**Version**: 2025-10-17

Validation

• [ ] Replaces simple variables correctly
• [ ] Handles nested properties
• [ ] Supports multiple syntax formats
• [ ] Handles missing variables gracefully
• [ ] Converts types to strings
• [ ] Preserves formatting (line breaks, indentation)
• [ ] Detects circular references
• [ ] Returns clear error messages

Supporting Files

None required - pure template rendering logic.

Integration with Other Skills

This Skill consolidates formatting logic used by:

• format-commit-message: Use render-template for message formatting
• generate-report-header: Use render-template for header generation
• format-todo-list: Use render-template for activeForm generation
• generate-changelog: Use render-template for section formatting

Example Integration:

Instead of: Hard-coded string formatting in each Skill
Use: render-template Skill with predefined templates
Result: Consistent formatting, easier to maintain