Endpoint Duplicated In Documentation

Introduction

When building complex applications with FastAPI, it's common to use decorators and dependency injection to simplify code and reduce repetition. However, this can sometimes lead to unexpected issues, such as duplicated endpoints in the OpenAPI documentation. In this article, we'll explore the problem of duplicated endpoints and provide a solution using FastAPI, FastAPI-Utils, and Dependency Injector.

The Problem

Let's take a closer look at the code snippet provided earlier:

user_router = APIRouter(prefix="/user", tags=["Users"])

@cbv(user_router)
class UserController:
    @inject
    def __init__(self, user_service: UserService = Depends(Provide["user_service"])):
        self.user_service = user_service

    @user_router.post("/create")
    async def create_user(self, ...):
        return await self.user_service.create_user(...)

In this example, we're using the @cbv decorator from FastAPI-Utils to avoid repeating the same dependency injections in each endpoint. However, when we register our router with @cbv(user_router), the endpoint appears twice in the OpenAPI documentation.

The Cause

The issue arises from the way FastAPI-Utils handles dependency injection. When we use @cbv to inject dependencies, it creates a new instance of the router for each endpoint. This means that each endpoint is registered separately, resulting in duplicated routes in the OpenAPI documentation.

The Solution

To avoid having duplicated endpoints in the OpenAPI documentation, we need to configure FastAPI-Utils to use a single instance of the router for all endpoints. We can achieve this by using the include_router method instead of @cbv.

Here's an updated code snippet:

user_router = APIRouter(prefix="/user", tags=["Users"])

class UserController:
    def __init__(self, user_service: UserService = Depends(Provide["user_service"])):
        self.user_service = user_service

    @user_router.post("/create")
    async def create_user(self, ...):
        return await self.user_service.create_user(...)

# Include the router in the main application
app.include_router(user_router)

In this example, we've removed the @cbv decorator and instead used the include_router method to include the user_router in the main application. This ensures that only one instance of the router is created, resulting in a single endpoint in the OpenAPI documentation.

Configuring FastAPI-Utils

If you still want to use @cbv to inject dependencies, you can configure FastAPI-Utils to use a single instance of the router by setting the inject parameter to False. Here's an updated code snippet:

user_router = APIRouter(prefix="/user", tags=["Users"])

@cbv(user_router, inject=False)
class UserController:
    def __init__(self, user_service: UserService = Depends(Provide["user_service"])):
        self.user_service = user_service

    @user_router.post("/create")
    async def create_user(self, ...):
        return await self.user_service.create_user(...)

In this example, we've set the inject parameter to False to prevent FastAPI-Utils from creating a new instance of the router for each endpoint.

Conclusion

Introduction

In our previous article, we explored the issue of duplicated endpoints in the OpenAPI documentation when using FastAPI and FastAPI-Utils. We discussed the cause of the problem and provided solutions to avoid it. In this article, we'll answer some frequently asked questions (FAQs) related to this issue.

Q: What is the cause of duplicated endpoints in the OpenAPI documentation?

A: The cause of duplicated endpoints in the OpenAPI documentation is due to the way FastAPI-Utils handles dependency injection. When you use @cbv to inject dependencies, it creates a new instance of the router for each endpoint. This means that each endpoint is registered separately, resulting in duplicated routes in the OpenAPI documentation.

Q: How can I avoid having duplicated endpoints in the OpenAPI documentation?

A: To avoid having duplicated endpoints in the OpenAPI documentation, you can use the include_router method instead of @cbv. This ensures that only one instance of the router is created, resulting in a single endpoint in the OpenAPI documentation.

Q: Can I still use @cbv to inject dependencies and avoid duplicated endpoints?

A: Yes, you can still use @cbv to inject dependencies and avoid duplicated endpoints. To do this, you need to set the inject parameter to False when using @cbv. This prevents FastAPI-Utils from creating a new instance of the router for each endpoint.

Q: What are the benefits of using include_router instead of @cbv?

A: The benefits of using include_router instead of @cbv include:

• Avoiding duplicated endpoints in the OpenAPI documentation
• Simplifying your code by reducing the number of decorators and dependencies
• Improving performance by reducing the number of router instances created

Q: Can I use include_router with other FastAPI-Utils features, such as dependency injection?

A: Yes, you can use include_router with other FastAPI-Utils features, such as dependency injection. To do this, you need to pass the dependencies as arguments to the include_router method.

Q: How can I troubleshoot duplicated endpoints in the OpenAPI documentation?

A: To troubleshoot duplicated endpoints in the OpenAPI documentation, you can:

• Check your code for any unnecessary decorators or dependencies
• Use the include_router method instead of @cbv
• Set the inject parameter to False when using @cbv
• Use the FastAPI-Utils debug mode to identify any issues with your code

Conclusion

In conclusion, duplicated endpoints in the OpenAPI documentation can be a frustrating issue when using FastAPI and FastAPI-Utils. By understanding the cause of the problem and using the correct solutions, you can avoid this issue and ensure that your endpoints are listed only once in the documentation. Whether you choose to use @cbv or the include_router method, the key is to use a single instance of the router for all endpoints.