What are the four problems with getting dependencies directly inside your web functions, as listed in the chapter?

The four problems are testing, hidden dependencies, code duplication, and OpenAPI visibility.

Getting dependencies directly inside web functions creates four consequences. Testing is harder because you cannot test variations of the function that look up the dependency differently. Hidden dependencies arise because details of how the function gets what it needs are hidden, so external code changes could break it. Code duplication occurs when a common dependency lookup is repeated in multiple functions. OpenAPI visibility is reduced because FastAPI's automatic test page needs information from the dependency injection mechanism.