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BUGS.md

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Common Bugs for Full-Stack Developer Assessment

This document lists the intentional bugs introduced into the codebase that a full-stack developer should be able to identify and fix.

Backend Bugs

1. Type Mismatch in Array Length Check (resolvers.ts:14)

  • Location: backend/src/graphql/resolvers.ts
  • Issue: Comparing requestLog.length (number) with string "1000"
  • Fix: Change == "1000" to === 1000
  • Impact: Condition never evaluates to true, array grows indefinitely

2. Case-Sensitive Search (resolvers.ts:69-70)

  • Location: backend/src/graphql/resolvers.ts - searchTasks query
  • Issue: Search uses .includes() without case normalization
  • Fix: Convert both query and fields to lowercase: t.title.toLowerCase().includes(query.toLowerCase())
  • Impact: Users can't find tasks with different casing

3. No Input Validation (resolvers.ts:262-270)

  • Location: backend/src/graphql/resolvers.ts - createTask mutation
  • Issue: Empty or whitespace-only titles are allowed
  • Fix: Add validation: if (!title?.trim()) throw new Error("Title is required")
  • Impact: Can create tasks with empty titles

4. Missing Null Check (resolvers.ts:289-302)

  • Location: backend/src/graphql/resolvers.ts - updateTask mutation
  • Issue: Returns result[0] without checking if task exists
  • Fix: Add check: if (!result[0]) throw new Error("Task not found")
  • Impact: Returns undefined instead of error, crashes client

5. Race Condition in Task Movement (resolvers.ts:315-331)

  • Location: backend/src/graphql/resolvers.ts - moveTask mutation
  • Issue: No locking mechanism for concurrent drag operations
  • Fix: Implement optimistic locking or transaction with position recalculation
  • Impact: Concurrent moves can corrupt task positions

6. Hardcoded Database Credentials (db/index.ts:6)

  • Location: backend/src/db/index.ts
  • Issue: Fallback contains hardcoded password in code
  • Fix: Fail loudly if DATABASE_URL not set or use safer default
  • Impact: Security risk, credentials in version control

7. No Database Connection Error Handling (db/index.ts:9)

  • Location: backend/src/db/index.ts
  • Issue: App crashes immediately if database is unavailable
  • Fix: Add try-catch with proper error message and retry logic
  • Impact: Poor developer experience, unclear error messages

8. N+1 Query Problem (resolvers.ts:96-122)

  • Location: backend/src/graphql/resolvers.ts - Board.stats resolver
  • Issue: Multiple queries inside loops instead of batch query
  • Fix: Use JOIN or batch queries to fetch all data at once
  • Impact: Severe performance degradation with many columns/tasks

Frontend Bugs

9. Memory Leak - Uncleaned Interval (KanbanBoard.tsx:71-74)

  • Location: frontend/src/components/KanbanBoard.tsx
  • Issue: setInterval never cleaned up
  • Fix: Return cleanup function: return () => clearInterval(interval)
  • Impact: Memory leak, multiple intervals pile up

10. Missing useEffect Dependency Array (KanbanBoard.tsx:78-80)

  • Location: frontend/src/components/KanbanBoard.tsx
  • Issue: Effect runs on every render instead of when data changes
  • Fix: Add dependency array: }, [data?.board?.title]);
  • Impact: Excessive re-renders, performance issues

11. Using Index as React Key (KanbanBoard.tsx:217-224)

  • Location: frontend/src/components/KanbanBoard.tsx
  • Issue: Using index as key for reorderable columns
  • Fix: Use stable identifier: key={column.id}
  • Impact: React loses track of components, incorrect renders, lost state

12. No Error Handling on Drag (KanbanBoard.tsx:138-174)

  • Location: frontend/src/components/KanbanBoard.tsx - handleDragEnd
  • Issue: Mutation can fail silently
  • Fix: Wrap in try-catch, show error toast, revert optimistic update
  • Impact: Tasks appear moved but operation failed

13. No Validation Before Task Creation (KanbanBoard.tsx:116-121)

  • Location: frontend/src/components/KanbanBoard.tsx - handleAddTask
  • Issue: No validation, relies on backend
  • Fix: Add client-side validation before calling mutation
  • Impact: Unnecessary network requests, poor UX

14. No Confirmation for Delete (KanbanBoard.tsx:110-113)

  • Location: frontend/src/components/KanbanBoard.tsx - handleDeleteColumn
  • Issue: Deletes columns (and all tasks) without confirmation
  • Fix: Add confirmation dialog
  • Impact: Accidental data loss

15. Aggressive Polling (KanbanBoard.tsx:62-64)

  • Location: frontend/src/components/KanbanBoard.tsx
  • Issue: Polling every 1 second is excessive
  • Fix: Increase to 3-5 seconds or use WebSockets
  • Impact: Excessive network traffic, server load

16. Hardcoded API URL (main.tsx:8)

  • Location: frontend/src/main.tsx
  • Issue: GraphQL URI hardcoded, not using environment variables
  • Fix: Use import.meta.env.VITE_API_URL or similar
  • Impact: Can't configure different environments

17. No Error Handling on Board Creation (App.tsx:27-36)

  • Location: frontend/src/App.tsx - handleCreateBoard
  • Issue: Mutation can fail silently
  • Fix: Add try-catch with error notification
  • Impact: Silent failures, confusing UX

18. GraphQL Over-fetching (queries.ts:24-61)

  • Location: frontend/src/graphql/queries.ts - GET_BOARD query
  • Issue: Fetching unnecessary nested data (column for each task, siblingTasks)
  • Fix: Remove unused fields from query
  • Impact: Unnecessary data transfer, slower queries

19. Whitespace-Only Description (KanbanColumn.tsx:45-51)

  • Location: frontend/src/components/KanbanColumn.tsx - handleAddTask
  • Issue: Description not trimmed, can save whitespace-only strings
  • Fix: Trim description: newTaskDescription.trim() || undefined
  • Impact: Ugly whitespace stored in database

Configuration Bugs

20. Missing Bun Types (backend/tsconfig.json:13)

  • Location: backend/tsconfig.json
  • Issue: References "bun-types" but package is "@types/bun"
  • Fix: Remove types array or change to correct package name
  • Impact: TypeScript errors

21. Deprecated Drizzle Commands (backend/package.json:8-9)

  • Location: backend/package.json
  • Issue: Using old generate:pg and push:pg syntax
  • Fix: Update to drizzle-kit generate and drizzle-kit push
  • Impact: Commands may fail with newer drizzle-kit versions

Summary

Total Bugs: 21 issues across backend, frontend, and configuration

Categories:

  • Security: 1 (hardcoded credentials)
  • Performance: 3 (N+1 queries, aggressive polling, over-fetching)
  • Memory/Resource Leaks: 2 (uncleaned interval, missing cleanup)
  • Error Handling: 5 (no validation, missing null checks, silent failures)
  • Data Integrity: 3 (race conditions, no confirmations, empty data)
  • UX Issues: 4 (case-sensitive search, no validation feedback)
  • React Anti-patterns: 2 (index as key, missing dependencies)
  • Configuration: 2 (wrong types, deprecated commands)