Fix/sqlalchemy 2.0 compatibility - chapter6 UoW

[rickywesker]

Hi Harry! 👋

I'm a reader following along with the Cosmic Python book, and I really enjoyed Chapter 6 on the Unit of Work pattern!

While working through the exercises on the chapter_06_uow_exercise branch, I noticed the code wasn't compatible with SQLAlchemy 2.0, which caused some errors when running tests. So I made the necessary updates to get everything working smoothly.

Changes

• orm.py: Replace deprecated mapper() with registry.map_imperatively()
• repository.py: Replace session.query() with session.scalars(select())
• conftest.py: Replace clear_mappers() with mapper_registry.dispose()
• test_*.py: Wrap raw SQL strings with text()
• requirements.txt: Require sqlalchemy>=2.0

Test Results

All existing tests pass (20 passed, 3 skipped, 4 failed).
The 4 failed tests are expected - they are exercise-related tests designed to fail until the reader implements the UnitOfWork pattern.

I hope this PR can help other readers who encounter the same issue, and save them some debugging time! 🙏

Thank you for writing such a great book! 📚

[Copilot]

Pull request overview

This PR updates the Cosmic Python book Chapter 6 exercise code to be compatible with SQLAlchemy 2.0, migrating away from deprecated APIs to modern SQLAlchemy 2.0 patterns.

Changes:

• Replaced deprecated mapper() with registry.map_imperatively() in ORM configuration
• Updated repository queries from session.query() to session.scalars(select())
• Replaced clear_mappers() with mapper_registry.dispose() in test fixtures
• Wrapped raw SQL strings with text() for SQLAlchemy 2.0 compatibility
• Updated requirements to specify sqlalchemy>=2.0
• Consolidated mypy configuration for pytest and sqlalchemy imports

Reviewed changes

Copilot reviewed 23 out of 29 changed files in this pull request and generated 11 comments.

Show a summary per file

File	Description
src/allocation/adapters/orm.py	Updated to use registry and map_imperatively for SQLAlchemy 2.0
src/allocation/adapters/repository.py	Replaced session.query() with session.scalars(select())
tests/conftest.py	Updated mapper cleanup to use mapper_registry.dispose()
tests/integration/test_orm.py	Wrapped SQL strings with text(), contains critical bug in assertion order
tests/integration/test_repository.py	Wrapped SQL strings with text()
tests/integration/test_uow.py	Wrapped SQL strings with text()
requirements.txt	Specified sqlalchemy>=2.0 requirement
mypy.ini	Consolidated pytest and sqlalchemy ignore settings
README.md	Contains minor spelling error in documentation
tests/unit/test_*.py	New unit test files for exercises
tests/pytest.ini	New pytest configuration
tests/e2e/test_api.py	New end-to-end API tests
src/allocation/service_layer/*.py	New service layer files for UoW exercises
src/allocation/entrypoints/flask_app.py	New Flask application entrypoint
src/allocation/domain/model.py	Domain model definitions
src/allocation/config.py	Configuration for database and API connections
Dockerfile, docker-compose.yml, Makefile, .travis.yml, src/setup.py	Infrastructure and build configuration files

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