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Custom Policies

Create policies tailored to your organization’s standards and requirements.

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Creating a Custom Policy

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Step 1: Define the Policy

Create a YAML file in your repository: 
# policies/require-logging.yaml
id: require-logging
name: Require Structured Logging
description: |
  All API handlers must use the company logging library
  instead of console.log for proper log aggregation.

severity: warning
enabled: true

patterns:
  - type: regex
    value: "console\\.(log|debug|info|warn|error)\\s*\\("
    files:
      - "src/api/**/*.ts"
      - "src/handlers/**/*.ts"
    message: "Use logger instead of console in API handlers"

suggestions:
  - "Import the logger: import { logger } from '@company/logging'"
  - "Replace console.log with logger.info"
  - "Replace console.error with logger.error"

references:
  - url: https://wiki.company.com/logging-standards
    title: Company Logging Standards

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Step 2: Register the Policy

Add to .mergeguide.yaml: 
custom_policies:
  - ./policies/*.yaml
  - ./policies/**/*.yaml

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Step 3: Test the Policy

# Validate syntax
mergeguide check --policy ./policies/require-logging.yaml

# Test against your code
mergeguide check --policy ./policies/require-logging.yaml

# View policy details
mergeguide policies  # View active policies

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Step 4: Deploy

Commit the policy file to your repository. It will be automatically loaded.

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Real-World Examples

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Require Company Imports

Ensure internal packages are used: 
id: require-company-auth
name: Use Company Auth Library
description: External auth libraries are not approved; use @company/auth

severity: error
enabled: true

patterns:
  - type: regex
    value: "from ['\"]passport['\"]"
    message: "Use @company/auth instead of passport"

  - type: regex
    value: "from ['\"]jsonwebtoken['\"]"
    message: "Use @company/auth for JWT handling"

suggestions:
  - "Import from @company/auth: import { authenticate } from '@company/auth'"

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Enforce API Standards

Require specific response formats: 
id: api-response-format
name: Standard API Response Format
description: API responses must use the standard response wrapper

severity: warning
enabled: true

patterns:
  - type: regex
    value: "res\\.json\\(\\{(?!.*success|error)"
    files:
      - "src/api/**/*.ts"
    message: "API responses must use standard format with success/error field"

suggestions:
  - "Use apiResponse helper: return apiResponse.success(data)"
  - "For errors: return apiResponse.error(message, statusCode)"

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Database Query Standards

Enforce ORM usage: 
id: require-orm
name: Require ORM for Database Access
description: Direct SQL queries are not allowed; use the ORM

severity: error
enabled: true

patterns:
  - type: regex
    value: "\\.(query|execute)\\s*\\(['\"]\\s*(SELECT|INSERT|UPDATE|DELETE)"
    message: "Use ORM methods instead of raw SQL"

  - type: ast
    language: typescript
    value: |
      CallExpression[callee.property.name="raw"][arguments.0.type="Literal"]
    message: "Avoid .raw() queries; use ORM query builder"

suggestions:
  - "Use Repository pattern: userRepository.findById(id)"
  - "For complex queries, create a named query in the repository"

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React Component Standards

Enforce component patterns: 
id: react-component-standards
name: React Component Standards
description: Enforce team React patterns

severity: warning
enabled: true

patterns:
  - type: regex
    value: "class\\s+\\w+\\s+extends\\s+(React\\.)?Component"
    message: "Use functional components with hooks instead of class components"

  - type: regex
    value: "useEffect\\([^,]+\\)\\s*$"
    message: "useEffect must have a dependency array"

  - type: regex
    value: "any\\s*[;,)>]"
    files:
      - "src/components/**/*.tsx"
    message: "Avoid 'any' type in component props"

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Git Commit Standards

Enforce commit message format: 
id: commit-message-format
name: Commit Message Format
description: Commits must follow conventional commits format

severity: error
enabled: true

patterns:
  - type: commit-message
    value: "^(feat|fix|docs|style|refactor|test|chore)(\\(.+\\))?: .{10,}"
    message: "Commit must follow format: type(scope): description"

suggestions:
  - "Example: feat(auth): add OAuth2 support"
  - "Example: fix(api): handle null response"
  - "See https://conventionalcommits.org"

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Policy Organization

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Directory Structure

policies/
├── security/
│   ├── no-internal-secrets.yaml
│   └── require-auth-headers.yaml
├── quality/
│   ├── require-logging.yaml
│   └── no-deprecated-apis.yaml
├── standards/
│   ├── naming-conventions.yaml
│   └── file-structure.yaml
└── team-specific/
    ├── frontend-rules.yaml
    └── backend-rules.yaml

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Loading Policies

# .mergeguide.yaml
custom_policies:
  - ./policies/**/*.yaml

# Or selectively:
custom_policies:
  - ./policies/security/*.yaml
  - ./policies/quality/*.yaml

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Sharing Policies

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Organization-Wide Policies

Store in a shared repository: 
# policies-repo/.mergeguide-policies/
security/
quality/
standards/
Reference in projects: 
# .mergeguide.yaml
extends:
  - "@company/policies"  # npm package
  # or
  - "github:company/policies"  # GitHub repo

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Publishing as npm Package

{
  "name": "@company/mergeguide-policies",
  "version": "1.0.0",
  "files": ["policies/**/*.yaml"],
  "mergeguide": {
    "policies": "./policies"
  }
}

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Advanced Techniques

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Conditional Policies

Apply policies based on context: 
id: strict-production-checks
name: Strict Production Checks
enabled: true

conditions:
  branches:
    - main
    - release/*
  files:
    - "src/**"
    - "!src/**/*.test.*"

patterns:
  - type: regex
    value: "console\\."
    message: "No console statements in production code"

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Policy Inheritance

Extend built-in policies: 
id: company-secrets-policy
extends: no-hardcoded-secrets

# Add company-specific patterns
patterns:
  - type: regex
    value: "COMPANY_SECRET_\\w+"
    message: "Company secret pattern detected"

# Override settings
settings:
  detect_aws_keys: true
  custom_patterns:
    - "INTERNAL_API_KEY_\\w+"

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Multi-Language Policies

id: no-debug-logging
name: No Debug Logging
description: Remove debug logging before merge

patterns:
  - type: regex
    value: "console\\.debug"
    languages: [javascript, typescript]
    message: "Remove console.debug"

  - type: regex
    value: "logging\\.debug"
    languages: [python]
    message: "Remove logging.debug"

  - type: regex
    value: "log\\.Debug"
    languages: [go]
    message: "Remove log.Debug"

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Testing Custom Policies

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Unit Testing

# Create test file
cat > test-policy.ts << 'EOF'
console.log("This should trigger");
logger.info("This should not");
EOF

# Run policy
mergeguide check --policy ./policies/require-logging.yaml test-policy.ts

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Integration Testing

# policies/require-logging.test.yaml
policy: require-logging

tests:
  - name: "Should detect console.log"
    code: "console.log('test');"
    expect: violation

  - name: "Should allow logger.info"
    code: "logger.info('test');"
    expect: pass

  - name: "Should detect console.error"
    code: "console.error('error');"
    expect: violation
Run tests: 
mergeguide policies test ./policies/require-logging.yaml