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

When to Use

Triggers: "find duplicate code", "DRY violations", "refactor similar code", "detect code duplication", "similar validation logic", "repeated patterns", "copy-paste code", "exact duplicates"

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) ❌ ❌ Quick Start Workflow

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)

Parse both outputs, prioritize by severity

Step 4: Refactor (Claude Code with user approval)

Extract shared functions, consolidate patterns, verify tests

Reference Documentation

For detailed information, see:

Detection Commands - PMD CPD and Semgrep command details Complete Workflow - Detection, analysis, and presentation phases Refactoring Strategies - Approaches for addressing violations