fix: Add missing foreign key constraints for project removal (#254)

[jope-bm]

Summary

Fixes issue #254: Foreign key constraint failures when deleting projects with related entities.

• Root Cause: Migration 647e7a75e2cd recreated the project table but failed to re-establish foreign key constraints with CASCADE DELETE
• Impact: Users unable to delete projects containing entities, receiving FOREIGN KEY constraint failed errors
• Solution: Add missing foreign key constraint with CASCADE DELETE behavior to ensure proper cleanup

Changes Made

Database Migration

• Added migration a1b2c3d4e5f6_fix_project_foreign_keys.py to restore missing foreign key constraints
• Changes entity.project_id foreign key from ON DELETE: NO ACTION to ON DELETE: CASCADE
• Ensures automatic cleanup of related entities when projects are deleted

Comprehensive Database Tests

• Added comprehensive test file tests/db/test_issue_254_foreign_key_constraints.py
• Tests both the fix and reproduction scenarios to prevent regression
• Validates foreign key constraint behavior in test environment

Production Verification Script

• Added tests/test_production_cascade_delete.py for testing on actual production databases
• Creates automatic backups before testing
• Verifies schema configuration and functional cascade delete behavior
• Essential for confirming fix works in production SQLite with foreign key enforcement

Technical Details

Before Fix:

-- Foreign key without cascade delete
FOREIGN KEY(project_id) REFERENCES project (id)  -- Defaults to NO ACTION

After Fix:

-- Foreign key with cascade delete
FOREIGN KEY(project_id) REFERENCES project (id) ON DELETE CASCADE

Why Tests Originally Passed:

• Test environment uses in-memory SQLite without foreign key enforcement during schema creation
• Production uses filesystem SQLite with PRAGMA foreign_keys=ON
• This discrepancy masked the constraint issue until production verification script was created

Test Plan

• Unit Tests: pytest tests/db/test_issue_254_foreign_key_constraints.py -v
• Integration Tests: All existing repository and service tests pass
• Production Verification: python tests/test_production_cascade_delete.py
  • Before fix: ❌ FOREIGN KEY constraint failed
  • After fix: ✅ CASCADE DELETE working: Entity was automatically deleted
• Manual Testing: Verified project removal works correctly through CLI

Verification Results

Production Database Test Results:

🧪 TEST RESULTS:
  Schema has CASCADE DELETE: True
  CASCADE DELETE works: True  
✅ PASS: Foreign key constraints are properly configured with CASCADE DELETE

Key Validation Points:

• Foreign key constraints properly configured with ON DELETE CASCADE
• Project deletion succeeds without constraint errors
• Related entities are automatically cleaned up
• No data orphaning occurs

Breaking Changes

None. This is a pure bug fix that restores intended behavior.

Migration Safety

• Migration uses SQLAlchemy's batch_alter_table for safe constraint modification
• Handles cases where constraint may or may not already exist
• Includes proper rollback mechanism in downgrade()

🤖 Generated with Claude Code

[phernandez]

huh, I wonder how I missed that.