DRY Check Skill

Purpose: Prevent code duplication by scanning new/modified code against multi-mono shared libraries.

Use when:

• Running Standards Audit phase
• Reviewing pull requests for DRY violations
• Checking if utility function already exists
• Validating components use @metasaver/core-components
• Ensuring services use @metasaver/core-service-utils

Target libraries (packages/):

• @metasaver/core-utils - String helpers (capitalize, toKebabCase, toCamelCase), color helpers, style helpers (cn)
• @metasaver/core-service-utils - Service factory, middleware, auth, health checks
• @metasaver/core-database - Database client utilities
• @metasaver/core-agent-utils - Agent factory patterns
• @metasaver/core-mcp-utils - MCP server utilities
• @metasaver/core-workflow-utils - Workflow with HITL

Target components (components/):

• @metasaver/core-components - Core UI: ZButton, ZCard, ZDataTable, ZErrorBoundary, ZLoading
• @metasaver/core-layouts - Layouts: ZAdminLayout, ZUserDropdown, useImpersonation

---

What This Skill Catches

Violation Type	Library	Examples
String utilities	@metasaver/core-utils	capitalize(), toKebabCase(), toCamelCase()
Style utilities	@metasaver/core-utils	cn(), getColorClasses()
Service patterns	@metasaver/core-service-utils	createService(), authMiddleware(), healthCheck()
Database clients	@metasaver/core-database	createClient(), database types
Core UI components	@metasaver/core-components	ZButton, ZCard, ZDataTable, ZErrorBoundary
Layout components	@metasaver/core-layouts	ZAdminLayout, ZUserDropdown, useImpersonation

---

Workflow

1. Identify Modified Files

Get list of new/modified files from git:

# Staged files
git diff --cached --name-only --diff-filter=AM

# Uncommitted changes
git diff --name-only --diff-filter=AM

# Specific branch vs main
git diff main...HEAD --name-only --diff-filter=AM

Filter to code files only: .ts, .tsx, .js, .jsx

2. Extract Signatures

For each modified file, extract:

• Function signatures: export function functionName(), export const functionName = ()
• Type definitions: export type TypeName, export interface InterfaceName
• Component definitions: export function ComponentName(), export const ComponentName: React.FC
• Zod schemas: export const schemaName = z.object()

Use Grep tool with patterns from templates/extraction-patterns.txt

3. Scan Shared Libraries

For each extracted signature, check if similar exists in shared packages:

Scan multi-mono packages/:

# Search utils for function
grep -r "export.*functionName" packages/utils/src/

# Search service-utils for middleware/factory
grep -r "export.*functionName" packages/service-utils/src/

# Search database for client utilities
grep -r "export.*functionName" packages/database/src/

Scan multi-mono components/:

# Search core components
grep -r "export.*ZComponentName" components/core/src/

# Search layouts
grep -r "export.*ZLayoutName" components/layouts/src/

Use fuzzy matching for similar names (e.g., capitalize matches toCapitalize, capitalizeFirst)

4. Compare Implementations

If potential match found:

1. Read both implementations (new code vs library)
2. Compare function signatures and logic
3. Calculate similarity score (0-100%)
4. Flag if similarity > 70%

Comparison heuristics:

• Same parameter count and types = +30%
• Same return type = +20%
• Similar variable names = +20%
• Similar control flow = +30%

5. Generate Report

For each violation, output using format from templates/violation-report.txt:

❌ VIOLATION: [file]:[line] [signature]
   Duplicates: @metasaver/[package]/[module].[export]
   Similarity: [score]%
   FIX: import { [export] } from '@metasaver/[package]/[module]'

   [Brief comparison of implementations]

For clean scans:

✅ DRY CHECK PASSED
   Files scanned: [count]
   Signatures checked: [count]
   No duplications found

---

Output Format

See templates/violation-report.txt for complete format specification.

Console output example:

🔍 DRY CHECK: Scanning 3 modified files...

❌ VIOLATION: src/utils/text.ts:5 capitalize()
   Duplicates: @metasaver/core-utils.capitalize()
   Similarity: 95%
   FIX: import { capitalize } from '@metasaver/core-utils'

   Both implementations capitalize first letter using same algorithm.

❌ VIOLATION: src/components/Button.tsx:10 Button
   Duplicates: @metasaver/core-components.ZButton
   Similarity: 85%
   FIX: import { ZButton } from '@metasaver/core-components'

   Local Button component has same props and styling as ZButton.

📊 SUMMARY:
   Files scanned: 3
   Signatures checked: 12
   Violations: 2
   Clean signatures: 10

---

Examples

Example 1: String Helper Violation

Input:

// src/utils/text.ts
export function capitalize(str: string): string {
  return str.charAt(0).toUpperCase() + str.slice(1).toLowerCase();
}

Output:

❌ VIOLATION: src/utils/text.ts:2 capitalize()
   Duplicates: @metasaver/core-utils.capitalize()
   Similarity: 100%
   FIX: import { capitalize } from '@metasaver/core-utils'

Example 2: Component Duplication

Input:

// src/components/Button.tsx
export function Button({ children, variant, onClick }) {
  return (
    <button className={buttonVariants({ variant })} onClick={onClick}>
      {children}
    </button>
  );
}

Output:

❌ VIOLATION: src/components/Button.tsx:2 Button
   Duplicates: @metasaver/core-components.ZButton
   Similarity: 90%
   FIX: import { ZButton } from '@metasaver/core-components'

Example 3: Clean Scan

Input: 3 modified files with unique implementations

Output:

✅ DRY CHECK PASSED
   Files scanned: 3
   Signatures checked: 8
   No duplications found

---

Template Files

• templates/extraction-patterns.txt - Regex patterns for extracting signatures
• templates/violation-report.txt - Output format specification
• templates/scan-script.sh.template - Shell script for batch scanning

---

Tool Usage

Step	Tool	Purpose
1	Bash	Run git diff to get modified files
2	Grep	Extract function/type signatures
3	Bash/Grep	Search shared library packages
4	Read	Compare implementations
5	Direct output	Format and display results

---

Related Skills

• /skill cross-cutting/coding-standards - DRY principle reference
• /skill cross-cutting/serena-code-reading - Code analysis workflow
• /skill domain/monorepo-audit - Monorepo structure validation