phx-techdebt

Name: phx-techdebt
Author: oliver-kriska/claude-elixir-phoenix

$npx mdskill add oliver-kriska/claude-elixir-phoenix/phx-techdebt

Analyze Elixir/Phoenix code for duplication and refactoring opportunities.

Detects duplicate code patterns and anti-patterns in Elixir/Phoenix projects.
Uses Credo for automated analysis and Grep for pattern searching.
Applies three strikes rule and prefers composition over inheritance.
Outputs prioritized list of refactoring opportunities with test coverage requirements.

SKILL.md

.github/skills/phx-techdebtView on GitHub ↗

---
name: phx-techdebt
description: Analyze Elixir/Phoenix technical debt — duplicates, refactoring opportunities,
  credo issues. Use when asked about code quality, cleanup, or what to improve.
---

# Technical Debt Detection

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

## Iron Laws - Never Violate These

1. **Search before refactoring** - Understand full scope of duplication before extracting
2. **Three strikes rule** - Extract shared code only after 3+ duplications
3. **Prefer composition** - Use behaviours and protocols over inheritance-style abstractions
4. **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:

1. **Location**: File paths and line numbers
2. **Pattern**: What code is duplicated
3. **Extraction**: Suggested shared function/module
4. **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.

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ecto:n1-check	Detect N+1 query anti-patterns specifically — Repo calls inside Enum/for loops, missing preloads on associations. Use when N+1 is explicitly suspected, NOT for unrelated Ecto questions or wider database performance.