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code-clone-assistant

Detect and refactor code duplication with PMD CPD. TRIGGERS - code clones, DRY violations, duplicate code.

personAuthor: jakexiaohubgithub
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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: