Pass endpoint dependencies to Jinja context via request.state

[hasansezertasan]

Related to #4

What is request.state and why am I using it?

https://github.com/encode/starlette/blob/433da65fc1431754dae0c3c87290b0421aa4a6f9/starlette/datastructures.py#L680-L685

Request State documentation says: An object that can be used to store arbitrary state.

I saw many implementations using the request.state to carry database sessions, current user, client sessions, etc. I think it's the best way to pass endpoint dependencies to the Jinja context without affecting anything.

[volfpeter]

What if someone already uses depends in there? It may be unlikely, but it's still not something a package should do. Also, its usage wouldn't be obvious to people, because its a bit of hidden magic. Explicit is better than implicit. I'll post my recommended solution in the issue.

[hasansezertasan]

What if someone already uses depends in there? It may be unlikely, but it's still not something a package should do.

I disagree, there are quite a lot of (popular) packages that follow this approach but you are right, depends might be used by another package, and still, we are passing that data to the Jinja Template file and returning the HTML response.

Also, its usage wouldn't be obvious to people, because its a bit of hidden magic. Explicit is better than implicit. I'll post my recommended solution in the issue.

You are right about that but we can document it, the only advantage of this approach is to provide a way to access the dependencies without overriding the Jinja class.

[hasansezertasan]

I'd like to mention this comment from the author of starlette: encode/starlette#659 (comment)

The recommended way is this: "For per-request information you can use request.state to store any additional information."

Other related issues:

• Generic interface for storing per-request state. encode/starlette#379
• AssertionError with middleware and TemplateResponse encode/starlette#472
• Future-proof way to access a global DB object encode/starlette#658

So this is actually the recommended way of doing such a thing.

[volfpeter]

This may be the recommended way for certain use-cases in application development (always opinionated code and always in the hand of its developer), but I don't think it's good behavior for a Python package, because it could break applications.

[hasansezertasan]

I also want to highlight these resources:

• Requests - Starlette
• Lifespan - Starlette
• SQL (Relational) Databases - FastAPI

I see that this is the "official" recommendation from the Starlette dev team. I also want to highlight some third-party-extensions that use request.state.something to store pre-request state/data.

• muicss/starlette-wtf: Simple integration of Starlette and WTForms
• apitally/python-client: Apitally client library for Python
• lepture/authlib: The ultimate Python library in building OAuth, OpenID Connect clients and servers. JWS,JWE,JWK,JWA,JWT included.
• jockerz/Starlette-Login: User session management for Starlette
• alex-oleshkevich/starception: Beautiful exception page for Starlette apps.
• jowilf/starlette-admin: Fast, beautiful and extensible administrative interface framework for Starlette & FastApi applications

Some other resources:

• I do recommend reading: Best practice to acessing context of a request outside a controller? · litestar-org · Discussion #1100 and going deeper at the referenced resources.
• The Request Context — Flask Documentation (3.0.x)
• The Application Context — Flask Documentation (3.0.x)

I believe there is no harm in using request.state._depends and update the README accordingly (in case someone uses that keyword for something else, it'll be a warning).

In the end, what do application and request context even exist for?