_merge_lifespan_context() — fastapi Function Reference

Architecture documentation for the _merge_lifespan_context() function in routing.py from the fastapi codebase.

Function python FastAPI Routing called by 1

Entity Profile

FastAPI→ Routing→ _merge_lifespan_context() — fastapi Function Reference

Dependency Diagram

graph TD
  691c784a_b40c_6e15_04d5_454eb7f51d69["_merge_lifespan_context()"]
  de395a51_26f8_3424_1af0_2f5bef39c893["routing.py"]
  691c784a_b40c_6e15_04d5_454eb7f51d69 -->|defined in| de395a51_26f8_3424_1af0_2f5bef39c893
  c1d02f65_9a84_123a_bdd4_304e5732f35a["include_router()"]
  c1d02f65_9a84_123a_bdd4_304e5732f35a -->|calls| 691c784a_b40c_6e15_04d5_454eb7f51d69
  style 691c784a_b40c_6e15_04d5_454eb7f51d69 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

fastapi/routing.py lines 196–210

def _merge_lifespan_context(
    original_context: Lifespan[Any], nested_context: Lifespan[Any]
) -> Lifespan[Any]:
    @asynccontextmanager
    async def merged_lifespan(
        app: AppType,
    ) -> AsyncIterator[Optional[Mapping[str, Any]]]:
        async with original_context(app) as maybe_original_state:
            async with nested_context(app) as maybe_nested_state:
                if maybe_nested_state is None and maybe_original_state is None:
                    yield None  # old ASGI compatibility
                else:
                    yield {**(maybe_nested_state or {}), **(maybe_original_state or {})}

    return merged_lifespan  # type: ignore[return-value]