# Bug Impact Analyzer > Analyzes bug fix blast radius. Determines affected code, dependencies, callers/callees, and potential side effects of changes. - Skill: `tomevault-io/bug-impact-analyzer` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/bug-impact-analyzer` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/bug-impact-analyzer/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/bug-impact-analyzer --- # Bug Impact Analyzer Systematic analysis of how a bug fix will affect the codebase. ## Blast Radius Concept Every code change has a "blast radius" - the scope of code that could be affected. ``` ┌─────────────────┐ │ Direct Fix │ ← Minimal blast radius │ (1 method) │ └────────┬────────┘ │ ┌──────────────┼──────────────┐ ▼ ▼ ▼ ┌─────────┐ ┌─────────┐ ┌─────────┐ │ Caller 1│ │ Caller 2│ │ Caller 3│ ← Medium blast radius └────┬────┘ └────┬────┘ └────┬────┘ │ │ │ ┌────────┴────────┬─────┴─────┬────────┴────────┐ ▼ ▼ ▼ ▼ ┌───────┐ ┌───────┐ ┌───────┐ ┌───────┐ │Public │ │ Event │ │ Test │ │ API │ ← Large blast radius │ API │ │Handler│ │ Suite │ │Client │ └───────┘ └───────┘ └───────┘ └───────┘ ``` ## Analysis Dimensions ### 1. Direct Callers Analysis Find all code that directly calls the changed method. ```bash # Find callers of a method grep -rn "->methodName(" src/ grep -rn "::methodName(" src/ # Find callers in tests grep -rn "->methodName(" tests/ ``` **Impact Questions:** - Will callers still work with the fix? - Do callers expect the old behavior? - Are there callers in external packages? ### 2. Callees Analysis (Dependencies) Find all code that the changed method calls. ```php // Example: Method being fixed public function calculateTotal(array $items): Money { // Callees: $sum = Money::zero($this->currency); // 1. Money::zero() foreach ($items as $item) { $price = $item->getPrice(); // 2. Item::getPrice() $quantity = $item->getQuantity(); // 3. Item::getQuantity() $sum = $sum->add($price->multiply($quantity)); // 4. Money::add(), Money::multiply() } return $sum; } ``` **Impact Questions:** - Does the fix change how callees are used? - Are new callees introduced? - Could new callees throw exceptions? ### 3. Data Flow Analysis Trace how data flows through the system. ``` Input Data Flow: Request → DTO → Command → Entity → Repository → Database ↓ Validation ↓ [BUG HERE] - invalid data passed forward Fix Impact: - Validation added at Command level - All downstream code now receives valid data - Callers must handle ValidationException ``` ### 4. Event/Message Impact Check if the change affects published events or messages. ```php // If the buggy method publishes events: class OrderService { public function completeOrder(Order $order): void { // BUG FIX HERE $order->complete(); // EVENT PUBLISHED - fix might change event data $this->eventBus->publish(new OrderCompleted($order)); } } ``` **Impact Questions:** - Does the fix change event payload? - Are there subscribers depending on old data? - Are events used for external integration? ### 5. API Contract Analysis Check if the change affects public APIs. | Change Type | API Impact | Severity | |-------------|------------|----------| | Return type change | Breaking | High | | New exception type | Breaking | High | | New required parameter | Breaking | High | | New optional parameter | Compatible | Low | | Different return value (same type) | Semantic breaking | Medium | | Performance change | SLA impact | Medium | ### 6. Database Impact Check if the fix affects database state. ```php // Fix that changes data format // BEFORE: stored as "2024-01-15" // AFTER: stored as "2024-01-15T00:00:00Z" // Impact: // - Existing data incompatible // - Need migration // - Other services reading same data affected ``` **Impact Questions:** - Does fix change data format? - Is migration needed? - Are other services affected? ## Impact Assessment Matrix ### Severity Levels | Level | Description | Action Required | |-------|-------------|-----------------| | **Low** | Internal implementation only | Fix and test | | **Medium** | Affects callers within same bounded context | Verify all callers | | **High** | Affects public API or other contexts | Coordinate with stakeholders | | **Critical** | Affects external integrations | Version API, migration plan | ### Assessment Checklist ```markdown ## Impact Assessment: [Bug ID] ### Direct Impact (Low) - [ ] Method signature unchanged - [ ] Return type unchanged - [ ] Exceptions unchanged - [ ] Side effects unchanged ### Caller Impact (Medium) - [ ] All callers identified: [count] - [ ] Callers tested: [count] - [ ] No behavioral changes for callers ### Cross-Context Impact (High) - [ ] Events payload unchanged - [ ] Messages format unchanged - [ ] Shared database schema unchanged ### External Impact (Critical) - [ ] Public API unchanged - [ ] SDK compatibility maintained - [ ] Documentation update not needed ### Overall Blast Radius: [Low/Medium/High/Critical] ``` ## Dependency Graph Building ### Step 1: Identify Changed Code ```php // File: src/Domain/Order/OrderService.php // Method: calculateTotal() // Line: 45-60 ``` ### Step 2: Find Direct Dependents ```bash # Classes that use OrderService grep -rn "OrderService" src/ --include="*.php" # Results: # src/Application/UseCase/CreateOrderUseCase.php:15 # src/Application/UseCase/UpdateOrderUseCase.php:18 # src/Presentation/Api/OrderController.php:22 ``` ### Step 3: Build Dependency Tree ``` OrderService::calculateTotal() ├── CreateOrderUseCase (calls calculateTotal) │ ├── OrderController::create() (calls UseCase) │ │ └── POST /api/orders (HTTP endpoint) │ └── CreateOrderFromCartHandler (event handler) │ └── CartCheckoutCompleted (event trigger) │ ├── UpdateOrderUseCase (calls calculateTotal) │ ├── OrderController::update() (calls UseCase) │ │ └── PUT /api/orders/{id} (HTTP endpoint) │ └── AddItemToOrderHandler (command handler) │ └── OrderTotalRecalculationJob (calls calculateTotal) └── Scheduler (cron trigger) ``` ### Step 4: Assess Each Branch | Dependent | Risk | Needs Testing | Notes | |-----------|------|---------------|-------| | CreateOrderUseCase | Medium | Yes | Core flow | | UpdateOrderUseCase | Medium | Yes | Core flow | | OrderController::create | Low | Covered | Via UseCase test | | OrderController::update | Low | Covered | Via UseCase test | | CreateOrderFromCartHandler | High | Yes | Async, hard to debug | | OrderTotalRecalculationJob | High | Yes | Background job | ## Side Effects Mapping ### Intentional Side Effects ```php class OrderService { public function completeOrder(Order $order): void { $order->complete(); // State change $this->repository->save($order); // Database write $this->eventBus->publish($event); // Event published $this->metrics->increment('orders.completed'); // Metrics $this->logger->info('Order completed'); // Logging } } ``` ### Side Effect Impact Table | Side Effect | Preserved After Fix? | Impact if Changed | |-------------|---------------------|-------------------| | Entity state change | Must preserve | Breaks domain logic | | Database write | Must preserve | Data inconsistency | | Event publish | Check payload | Downstream handlers affected | | Metrics | Should preserve | Dashboard/alerts affected | | Logging | Can change | Low impact | ## Test Coverage Analysis ### Finding Existing Tests ```bash # Tests for the class being fixed grep -rn "OrderService" tests/ --include="*.php" # Tests that might break grep -rn "calculateTotal" tests/ --include="*.php" ``` ### Coverage Gaps ```markdown ## Test Coverage for OrderService::calculateTotal() ### Existing Tests - [x] OrderServiceTest::testCalculateTotalWithItems - [x] OrderServiceTest::testCalculateTotalEmpty - [ ] Missing: testCalculateTotalWithNullItem ← Bug case ### Integration Tests - [x] CreateOrderUseCaseTest - [ ] Missing: UpdateOrderUseCaseTest ### E2E Tests - [x] POST /api/orders - [ ] Missing: PUT /api/orders/{id} ``` ## Quick Impact Commands ```bash # Find all files that import/use the changed class grep -rln "use.*OrderService" src/ # Find all method calls grep -rn "->calculateTotal(" src/ tests/ # Find event subscribers grep -rn "OrderCompleted" src/ # Find API routes using the controller grep -rn "OrderController" routes/ # Count affected files grep -rln "OrderService" src/ | wc -l ``` ## Impact Report Template ```markdown # Impact Analysis Report ## Bug: [ID/Description] ## Fix Location: [File:Line] ## Blast Radius Summary | Dimension | Count | Risk | |-----------|-------|------| | Direct Callers | X | Low/Med/High | | Event Handlers | X | Low/Med/High | | API Endpoints | X | Low/Med/High | | Database Tables | X | Low/Med/High | | External Services | X | Low/Med/High | ## Detailed Impact ### Callers Affected 1. [Caller 1] - [Impact description] 2. [Caller 2] - [Impact description] ### Events Affected 1. [Event 1] - [Payload change?] ### APIs Affected 1. [Endpoint 1] - [Response change?] ## Testing Requirements - [ ] Unit test for fix - [ ] Integration tests for callers - [ ] E2E tests for APIs - [ ] Manual testing for [scenarios] ## Rollout Recommendation - [ ] Safe for immediate deployment - [ ] Requires staged rollout - [ ] Requires feature flag - [ ] Requires coordination with [teams] ``` --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/dykyi-roman) — claim your Tome and manage your conversions.