Duplicate code detector: flag copy-paste and suggest refactors

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2name: Duplicate Code Detector3description: Identifies duplicate code patterns across the codebase and suggests refactoring opportunities4

5on:6  workflow_dispatch:7  schedule: daily8

9permissions:10  contents: read11  issues: read12  pull-requests: read13

14safe-outputs:15  create-issue:16    expires: 2d17    title-prefix: "[duplicate-code] "18    labels: [code-quality, automated-analysis]19    assignees: copilot20    group: true21    max: 32223timeout-minutes: 1524---2526# Duplicate Code Detection2728Analyze code to identify duplicated patterns using semantic analysis. Report significant findings that require refactoring.2930## Task3132Detect and report code duplication by:33341. **Analyzing Recent Commits**: Review changes in the latest commits352. **Detecting Duplicated Code**: Identify similar or duplicated code patterns using semantic analysis363. **Reporting Findings**: Create a detailed issue if significant duplication is detected (threshold: >10 lines or 3+ similar patterns)3738## Context3940- **Repository**: ${{ github.repository }}41- **Commit ID**: ${{ github.event.head_commit.id }}42- **Triggered by**: @${{ github.actor }}4344## Analysis Workflow4546### 1. Changed Files Analysis4748Identify and analyze modified files:49- Determine files changed in the recent commits using `git log` and `git diff`50- Focus on source code files (programming language files)51- **Exclude test files** from analysis (files matching patterns: `*_test.*`, `*.test.*`, `*.spec.*`, `test_*.*`, or located in directories named `test`, `tests`, `__tests__`, or `spec`)52- **Exclude generated files** and build artifacts53- **Exclude workflow files** from analysis (files under `.github/workflows/*`)54- Use code exploration tools to understand file structure55- Read modified file contents to examine changes5657### 2. Duplicate Detection5859Apply analysis to find duplicates:6061**Pattern Search**:62- Search for duplication indicators using grep and code search:63  - Similar function signatures64  - Repeated logic blocks65  - Similar variable naming patterns66  - Near-identical code blocks67- Look for functions with similar names across different files68- Identify structural similarities in code organization6970**Semantic Analysis**:71- Compare code blocks for logical similarity beyond textual matching72- Identify different implementations of the same functionality73- Look for copy-paste patterns with minor variations7475### 3. Duplication Evaluation7677Assess findings to identify true code duplication:7879**Duplication Types**:80- **Exact Duplication**: Identical code blocks in multiple locations81- **Structural Duplication**: Same logic with minor variations (different variable names, etc.)82- **Functional Duplication**: Different implementations of the same functionality83- **Copy-Paste Programming**: Similar code blocks that could be extracted into shared utilities8485**Assessment Criteria**:86- **Severity**: Amount of duplicated code (lines of code, number of occurrences)87- **Impact**: Where duplication occurs (critical paths, frequently called code)88- **Maintainability**: How duplication affects code maintainability89- **Refactoring Opportunity**: Whether duplication can be easily refactored9091### 4. Issue Reporting9293Create separate issues for each distinct duplication pattern found (maximum 3 patterns per run). Each pattern should get its own issue to enable focused remediation.9495**When to Create Issues**:96- Only create issues if significant duplication is found (threshold: >10 lines of duplicated code OR 3+ instances of similar patterns)97- **Create one issue per distinct duplication pattern** - do NOT bundle multiple patterns in a single issue98- Limit to the top 3 most significant patterns if more are found99- Use the `create_issue` tool from safe-outputs MCP **once for each pattern**100101**Issue Contents for Each Pattern**:102- **Executive Summary**: Brief description of this specific duplication pattern103- **Duplication Details**: Specific locations and code blocks for this pattern only104- **Severity Assessment**: Impact and maintainability concerns for this pattern105- **Refactoring Recommendations**: Suggested approaches to eliminate this pattern106- **Code Examples**: Concrete examples with file paths and line numbers for this pattern107108## Detection Scope109110### Report These Issues111112- Identical or nearly identical functions in different files113- Repeated code blocks that could be extracted to utilities114- Similar classes or modules with overlapping functionality115- Copy-pasted code with minor modifications116- Duplicated business logic across components117118### Skip These Patterns119120- Standard boilerplate code (imports, exports, package declarations)121- Test setup/teardown code (acceptable duplication in tests)122- **All test files** (files matching: `*_test.*`, `*.test.*`, `*.spec.*`, `test_*.*`, or in `test/`, `tests/`, `__tests__/`, `spec/` directories)123- **All workflow files** (files under `.github/workflows/*`)124- Configuration files with similar structure125- Language-specific patterns (constructors, getters/setters)126- Small code snippets (<5 lines) unless highly repetitive127- Generated code or vendored dependencies128129### Analysis Depth130131- **Primary Focus**: Files changed in recent commits (excluding test files and workflow files)132- **Secondary Analysis**: Check for duplication with existing codebase133- **Cross-Reference**: Look for patterns across the repository134- **Historical Context**: Consider if duplication is new or existing135136## Issue Template137138For each distinct duplication pattern found, create a separate issue using this structure:139140~~~`markdown141# 🔍 Duplicate Code Detected: [Pattern Name]142143*Analysis of commit ${{ github.event.head_commit.id }}*144145**Assignee**: @copilot146147## Summary148149[Brief overview of this specific duplication pattern]150151## Duplication Details152153### Pattern: [Description]154- **Severity**: High/Medium/Low155- **Occurrences**: [Number of instances]156- **Locations**:157  - `path/to/file1.ext` (lines X-Y)158  - `path/to/file2.ext` (lines A-B)159- **Code Sample**:160  ~~~`[language]161  [Example of duplicated code]162  ~~~`163164## Impact Analysis165166- **Maintainability**: [How this affects code maintenance]167- **Bug Risk**: [Potential for inconsistent fixes]168- **Code Bloat**: [Impact on codebase size]169170## Refactoring Recommendations1711721. **[Recommendation 1]**173   - Extract common functionality to: `suggested/path/utility.ext`174   - Estimated effort: [hours/complexity]175   - Benefits: [specific improvements]1761772. **[Recommendation 2]**178   [... additional recommendations ...]179180## Implementation Checklist181182- [ ] Review duplication findings183- [ ] Prioritize refactoring tasks184- [ ] Create refactoring plan185- [ ] Implement changes186- [ ] Update tests187- [ ] Verify no functionality broken188189## Analysis Metadata190191- **Analyzed Files**: [count]192- **Detection Method**: Semantic code analysis193- **Commit**: ${{ github.event.head_commit.id }}194- **Analysis Date**: [timestamp]195~~~`196197## Operational Guidelines198199### Security200- Never execute untrusted code or commands201- Only use read-only analysis tools202- Do not modify files during analysis203204### Efficiency205- Focus on recently changed files first206- Use semantic analysis for meaningful duplication, not superficial matches207- Stay within timeout limits (balance thoroughness with execution time)208209### Accuracy210- Verify findings before reporting211- Distinguish between acceptable patterns and true duplication212- Consider language-specific idioms and best practices213- Provide specific, actionable recommendations214215### Issue Creation216- Create **one issue per distinct duplication pattern** - do NOT bundle multiple patterns in a single issue217- Limit to the top 3 most significant patterns if more are found218- Only create issues if significant duplication is found219- Include sufficient detail for coding agents to understand and act on findings220- Provide concrete examples with file paths and line numbers221- Suggest practical refactoring approaches222- Assign issue to @copilot for automated remediation223- Use descriptive titles that clearly identify the specific pattern (e.g., "Duplicate Code: Error Handling Pattern in Parser Module")224225**Objective**: Improve code quality by identifying and reporting meaningful code duplication that impacts maintainability. Focus on actionable findings that enable automated or manual refactoring.