linkd.ext.fastapi

Extension module adding support for using linkd-based dependency injection with FastAPI.

See the examples directory for a full working application using this module.

---

final class Contexts

Collection of the dependency injection context values linkd.ext.fastapi uses.

REQUEST = 'linkd.contexts.http.request'

DI context used during HTTP request handling.

ROOT = 'linkd.contexts.root'

The root DI context - ALL other contexts are built with this as the parent.

class RequestContainer(registry: registry_.Registry, *, parent: Container | None = None, tag: Context | None = None)

class RootContainer(registry: registry_.Registry, *, parent: Container | None = None, tag: Context | None = None)

inject(func: InjectedCallableT) → InjectedCallableT

Specialised decorator enabling linkd-managed dependency injection for fastapi request handlers.

This decorator MUST be placed below the fastapi route decorator if it is being used.

Parameters:

func – The function to enable DI for.

Returns:

The function with dependency injection enabled.

Warning

The standard inject() decorator WILL NOT work for fastapi request handlers and this decorator MUST be used in its place.

Warning

Linkd-injected parameters MUST be keyword-only, as this decorator rewrites the function signature to hide those parameters from fastapi, so that you can still use fastapi dependency injection on non-kw-only parameters. See the example for more.

Example

import fastapi
import linkd

manager = linkd.DependencyInjectionManager()

app = fastapi.FastAPI()
linkd.ext.fastapi.use_di_context_middleware(app, manager)

@app.get(...)
@linkd.ext.fastapi.inject
async def some_handler(
    # this parameter will be injected by fastapi - path parameter, query parameter, etc.
    foo: str
    # custom fastapi dependencies using 'Depends' are also supported
    bar: Annotated[dict, Depends(some_dependency)],
    # '*' IS IMPORTANT - if excluded, fastapi will complain about the remaining parameters
    *,
    # this parameter will be ignored by fastapi, and injected by linkd instead
    baz: SomeDependency,
) -> None:
    ...

use_di_context_middleware(app: fastapi.FastAPI, manager: _solver.DependencyInjectionManager) → None

Adds middleware to the given fastapi application to handle setting up a DI context for each HTTP request.

Parameters:

• app – The fastapi application to add the middleware to.

• manager – The dependency injection manager to use when entering the DI context.

Returns:

None

Example

import fastapi
import linkd

manager = linkd.DependencyInjectionManager()

app = fastapi.FastAPI()
linkd.ext.fastapi.use_di_context_middleware(app, manager)