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

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)
# 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

Search AI Tools

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Install this agent skill to your Project

SKILL.md