Phx Techdebt Skill for Claude

Technical Debt Detection

Find and eliminate duplicate code patterns, anti-patterns, and refactoring opportunities in Elixir/Phoenix projects.

Iron Laws - Never Violate These

• Search before refactoring - Understand full scope of duplication before extracting
• Three strikes rule - Extract shared code only after 3+ duplications
• Prefer composition - Use behaviours and protocols over inheritance-style abstractions
• Test coverage first - Ensure tests exist before refactoring duplicated code

Analysis Checklist

1. Run Credo for Automated Detection

Run mix credo --strict.

Focus on:

• Design issues (duplication, complexity)
• Consistency issues (naming, patterns)
• Refactoring opportunities

2. Find Duplicate Ecto Query Patterns

Use Grep to search for repeated Repo calls (Repo.get!, Repo.get, Repo.one) in lib/**/*.ex.

Use Grep to find duplicate query patterns (from.*in.*where) in lib/**/*.ex.

3. Find Duplicate Validation Logic

Use Grep with output_mode: "count" to count def changeset occurrences in lib/**/*.ex.

Use Grep to find repeated validations (validate_required, validate_format) in lib/**/*.ex.

4. Find Copy-Pasted Controller Actions

Use Grep to find similar action patterns (def create, def update, def delete) in lib/*_web/**/*.ex.

Common Duplication Patterns

| Pattern | Symptom | Solution |

|---------|---------|----------|

| Repeated queries | Same Repo.get in multiple contexts | Create shared query module |

| Duplicate validations | Same validate_* calls | Extract to shared changeset |

| Similar controllers | Copy-pasted CRUD actions | Use Phoenix generators consistently |

| Repeated transforms | Same Enum.map patterns | Extract to domain module |

Reporting Format

For each duplication found, report:

• Location: File paths and line numbers
• Pattern: What code is duplicated
• Extraction: Suggested shared function/module
• Effort: Low/Medium/High to fix

Usage

Run /phx-techdebt to analyze the codebase and generate a prioritized report of technical debt with specific remediation steps.