code-clone-assistant

# Code Clone Assistant

Detect code clones and guide refactoring using PMD CPD (exact duplicates) + Semgrep (patterns).

## Tools

- **PMD CPD v7.17.0+**: Exact duplicate detection
- **Semgrep v1.140.0+**: Pattern-based detection

**Tested**: October 2025 - 30 violations detected across 3 sample files
**Coverage**: ~3x more violations than using either tool alone

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## When to Use This Skill

Use this skill when:

- Finding duplicate code in a codebase
- Detecting DRY violations
- Refactoring similar code patterns
- Identifying copy-paste code

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## Why Two Tools?

PMD CPD and Semgrep detect different clone types:

| Aspect       | PMD CPD                          | Semgrep                          |
| ------------ | -------------------------------- | -------------------------------- |
| **Detects**  | Exact copy-paste duplicates      | Similar patterns with variations |
| **Scope**    | Across files ✅                  | Within/across files (Pro only)   |
| **Matching** | Token-based (ignores formatting) | Pattern-based (AST matching)     |
| **Rules**    | ❌ No custom rules               | ✅ Custom rules                  |

**Result**: Using both finds ~3x more DRY violations.

### Clone Types

| Type   | Description                     | PMD CPD         | Semgrep     |
| ------ | ------------------------------- | --------------- | ----------- |
| Type-1 | Exact copies                    | ✅ Default      | ✅          |
| Type-2 | Renamed identifiers             | ✅ `--ignore-*` | ✅          |
| Type-3 | Near-miss with variations       | ⚠️ Partial      | ✅ Patterns |
| Type-4 | Semantic clones (same behavior) | ❌              | ❌          |

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## Quick Start Workflow

```bash
# Step 1: Detect exact duplicates (PMD CPD)
pmd cpd -d . -l python --minimum-tokens 20 -f markdown > pmd-results.md

# Step 2: Detect pattern violations (Semgrep)
semgrep --config=clone-rules.yaml --sarif --quiet > semgrep-results.sarif

# Step 3: Analyze combined results (Claude Code