@ -70,12 +70,22 @@ If you understood all this, you already know how those utility tools for securit
You most probably don't need these technical details.
These details are useful mainly if you had a FastAPI application older than 0.118.0 and you are facing issues with dependencies with `yield`.
These details are useful mainly if you had a FastAPI application older than 0.121.0 and you are facing issues with dependencies with `yield`.
///
Dependencies with `yield` have evolved over time to account for the different use cases and to fix some issues, here's a summary of what has changed.
### Dependencies with `yield` and `scope` { #dependencies-with-yield-and-scope }
In version 0.121.0, FastAPI added support for `Depends(scope="function")` for dependencies with `yield`.
Using `Depends(scope="function")`, the exit code after `yield` is executed right after the *path operation function* is finished, before the response is sent back to the client.
And when using `Depends(scope="request")` (the default), the exit code after `yield` is executed after the response is sent.
You can read more about it in the docs for [Dependencies with `yield` - Early exit and `scope`](../tutorial/dependencies/dependencies-with-yield.md#early-exit-and-scope).
### Dependencies with `yield` and `StreamingResponse`, Technical Details { #dependencies-with-yield-and-streamingresponse-technical-details }
Before FastAPI 0.118.0, if you used a dependency with `yield`, it would run the exit code after the *path operation function* returned but right before sending the response.
* 📝 Upate docs for advanced dependencies with `yield`, noting the changes in 0.121.0, adding `scope`. PR [#14287](https://github.com/fastapi/fastapi/pull/14287) by [@tiangolo](https://github.com/tiangolo).
### Internal
* ⬆ Bump ruff from 0.13.2 to 0.14.3. PR [#14276](https://github.com/fastapi/fastapi/pull/14276) by [@dependabot[bot]](https://github.com/apps/dependabot).
* ⬆ [pre-commit.ci] pre-commit autoupdate. PR [#14289](https://github.com/fastapi/fastapi/pull/14289) by [@pre-commit-ci[bot]](https://github.com/apps/pre-commit-ci).
## 0.121.0
### Features
* ✨ Add support for dependencies with scopes, support `scope="request"` for dependencies with `yield` that exit before the response is sent. PR [#14262](https://github.com/fastapi/fastapi/pull/14262) by [@tiangolo](https://github.com/tiangolo).
* New docs: [Dependencies with `yield` - Early exit and `scope`](https://fastapi.tiangolo.com/tutorial/dependencies/dependencies-with-yield/#early-exit-and-scope).
### Internal
* 👥 Update FastAPI People - Contributors and Translators. PR [#14273](https://github.com/fastapi/fastapi/pull/14273) by [@tiangolo](https://github.com/tiangolo).
* 👥 Update FastAPI People - Sponsors. PR [#14274](https://github.com/fastapi/fastapi/pull/14274) by [@tiangolo](https://github.com/tiangolo).
* ⬆ Bump mkdocs-macros-plugin from 1.4.0 to 1.4.1. PR [#14277](https://github.com/fastapi/fastapi/pull/14277) by [@dependabot[bot]](https://github.com/apps/dependabot).
* ⬆ Bump mkdocstrings[python] from 0.26.1 to 0.30.1. PR [#14279](https://github.com/fastapi/fastapi/pull/14279) by [@dependabot[bot]](https://github.com/apps/dependabot).
@ -184,6 +184,51 @@ If you raise any exception in the code from the *path operation function*, it wi
///
## Early exit and `scope` { #early-exit-and-scope }
Normally the exit code of dependencies with `yield` is executed **after the response** is sent to the client.
But if you know that you won't need to use the dependency after returning from the *path operation function*, you can use `Depends(scope="function")` to tell FastAPI that it should close the dependency after the *path operation function* returns, but **before** the **response is sent**.
`Depends()` receives a `scope` parameter that can be:
* `"function"`: start the dependency before the *path operation function* that handles the request, end the dependency after the *path operation function* ends, but **before** the response is sent back to the client. So, the dependency function will be executed **around** the *path operation **function***.
* `"request"`: start the dependency before the *path operation function* that handles the request (similar to when using `"function"`), but end **after** the response is sent back to the client. So, the dependency function will be executed **around** the **request** and response cycle.
If not specified and the dependency has `yield`, it will have a `scope` of `"request"` by default.
### `scope` for sub-dependencies { #scope-for-sub-dependencies }
When you declare a dependency with a `scope="request"` (the default), any sub-dependency needs to also have a `scope` of `"request"`.
But a dependency with `scope` of `"function"` can have dependencies with `scope` of `"function"` and `scope` of `"request"`.
This is because any dependency needs to be able to run its exit code before the sub-dependencies, as it might need to still use them during its exit code.
```mermaid
sequenceDiagram
participant client as Client
participant dep_req as Dep scope="request"
participant dep_func as Dep scope="function"
participant operation as Path Operation
client ->> dep_req: Start request
Note over dep_req: Run code up to yield
dep_req ->> dep_func: Pass dependency
Note over dep_func: Run code up to yield
dep_func ->> operation: Run path operation with dependency
operation ->> dep_func: Return from path operation
Note over dep_func: Run code after yield
Note over dep_func: ✅ Dependency closed
dep_func ->> client: Send response to client
Note over client: Response sent
Note over dep_req: Run code after yield
Note over dep_req: ✅ Dependency closed
```
## Dependencies with `yield`, `HTTPException`, `except` and Background Tasks { #dependencies-with-yield-httpexception-except-and-background-tasks }
Dependencies with `yield` have evolved over time to cover different use cases and fix some issues.
Adeniran John
9 months ago
GitHub