fastapi-slim doesn't play well with libraries built around fastapi

[edouardlp]

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Example Code

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Description

In #11503, fastapi now includes multiple dependencies that some users do not need. fastapi-slim was introduced as a separate package without the automatic inclusion of those dependencies. This is fine for direct users of fastapi who can choose to install the fastapi-slim package instead of fastapi, but this doesn't work for libraries that are non-optionally dependent on fastapi, such as https://github.com/dialoguemd/fastapi-sqla.

Maintainers of such repos must choose between 3 approaches :

1. Continue to require fastapi, thereby removing the ability for those library users to use fastapi-slim. Users technically could adopt fastapi-slim, but they would get 2 installations of the package, and would still get all dependencies.
2. Require fastapi-slim and force library users to switch to that. This is a breaking change given that users must change their direct requirement on fastapi, if they have it, so as to avoid a double installation of fastapi.
3. Offer both as optional dependencies and require one of this extra for the library to function (approach chosen here : Make FastAPI an optional dependency matyasrichter/fastapi-injector#30). This also requires library maintainers to implement a fallback mechanism to warn the user that they are lacking a required dependency.

Has anyone found a better workaround?

It seems to me like the approach that would make fastapi a better python citizen would be to revert back to using extras as intended : additional packages that enhance the functionality of the package, but aren't absolutely required.

Operating System

Linux, macOS

Operating System Details

No response

FastAPI Version

0.111.0

Pydantic Version

N/A

Python Version

N/A

Additional Context

No response

[edouardlp]

Related discussion #11525