Add support for ASGI lifespan

conformance/test/gen/connectrpc/conformance/v1/service_connect.py

@@ -1,7 +1,7 @@
 # Generated by https://github.com/connectrpc/connect-python.  DO NOT EDIT!
 # source: connectrpc/conformance/v1/service.proto
 
-from collections.abc import AsyncIterator, Iterable, Iterator, Mapping
+from collections.abc import AsyncGenerator, AsyncIterator, Iterable, Iterator, Mapping
 from typing import Protocol
 
 from connectrpc.client import ConnectClient, ConnectClientSync
@@ -72,16 +72,17 @@ async def idempotent_unary(
         raise ConnectError(Code.UNIMPLEMENTED, "Not implemented")
 
 
-class ConformanceServiceASGIApplication(ConnectASGIApplication):
+class ConformanceServiceASGIApplication(ConnectASGIApplication[ConformanceService]):
     def __init__(
         self,
-        service: ConformanceService,
+        service: ConformanceService | AsyncGenerator[ConformanceService],
         *,
         interceptors: Iterable[Interceptor] = (),
         read_max_bytes: int | None = None,
     ) -> None:
         super().__init__(
-            endpoints={
+            service=service,
+            endpoints=lambda svc: {
                 "/connectrpc.conformance.v1.ConformanceService/Unary": Endpoint.unary(
                     method=MethodInfo(
                         name="Unary",
@@ -90,7 +91,7 @@ def __init__(
                         output=connectrpc_dot_conformance_dot_v1_dot_service__pb2.UnaryResponse,
                         idempotency_level=IdempotencyLevel.UNKNOWN,
                     ),
-                    function=service.unary,
+                    function=svc.unary,
                 ),
                 "/connectrpc.conformance.v1.ConformanceService/ServerStream": Endpoint.server_stream(
                     method=MethodInfo(
@@ -100,7 +101,7 @@ def __init__(
                         output=connectrpc_dot_conformance_dot_v1_dot_service__pb2.ServerStreamResponse,
                         idempotency_level=IdempotencyLevel.UNKNOWN,
                     ),
-                    function=service.server_stream,
+                    function=svc.server_stream,
                 ),
                 "/connectrpc.conformance.v1.ConformanceService/ClientStream": Endpoint.client_stream(
                     method=MethodInfo(
@@ -110,7 +111,7 @@ def __init__(
                         output=connectrpc_dot_conformance_dot_v1_dot_service__pb2.ClientStreamResponse,
                         idempotency_level=IdempotencyLevel.UNKNOWN,
                     ),
-                    function=service.client_stream,
+                    function=svc.client_stream,
                 ),
                 "/connectrpc.conformance.v1.ConformanceService/BidiStream": Endpoint.bidi_stream(
                     method=MethodInfo(
@@ -120,7 +121,7 @@ def __init__(
                         output=connectrpc_dot_conformance_dot_v1_dot_service__pb2.BidiStreamResponse,
                         idempotency_level=IdempotencyLevel.UNKNOWN,
                     ),
-                    function=service.bidi_stream,
+                    function=svc.bidi_stream,
                 ),
                 "/connectrpc.conformance.v1.ConformanceService/Unimplemented": Endpoint.unary(
                     method=MethodInfo(
@@ -130,7 +131,7 @@ def __init__(
                         output=connectrpc_dot_conformance_dot_v1_dot_service__pb2.UnimplementedResponse,
                         idempotency_level=IdempotencyLevel.UNKNOWN,
                     ),
-                    function=service.unimplemented,
+                    function=svc.unimplemented,
                 ),
                 "/connectrpc.conformance.v1.ConformanceService/IdempotentUnary": Endpoint.unary(
                     method=MethodInfo(
@@ -140,7 +141,7 @@ def __init__(
                         output=connectrpc_dot_conformance_dot_v1_dot_service__pb2.IdempotentUnaryResponse,
                         idempotency_level=IdempotencyLevel.NO_SIDE_EFFECTS,
                     ),
-                    function=service.idempotent_unary,
+                    function=svc.idempotent_unary,
                 ),
             },
             interceptors=interceptors,

example/example/eliza_connect.py

@@ -1,7 +1,7 @@
 # Generated by https://github.com/connectrpc/connect-python.  DO NOT EDIT!
 # source: example/eliza.proto
 
-from collections.abc import AsyncIterator, Iterable, Iterator, Mapping
+from collections.abc import AsyncGenerator, AsyncIterator, Iterable, Iterator, Mapping
 from typing import Protocol
 
 from connectrpc.client import ConnectClient, ConnectClientSync
@@ -39,16 +39,17 @@ def introduce(
         raise ConnectError(Code.UNIMPLEMENTED, "Not implemented")
 
 
-class ElizaServiceASGIApplication(ConnectASGIApplication):
+class ElizaServiceASGIApplication(ConnectASGIApplication[ElizaService]):
     def __init__(
         self,
-        service: ElizaService,
+        service: ElizaService | AsyncGenerator[ElizaService],
         *,
         interceptors: Iterable[Interceptor] = (),
         read_max_bytes: int | None = None,
     ) -> None:
         super().__init__(
-            endpoints={
+            service=service,
+            endpoints=lambda svc: {
                 "/connectrpc.eliza.v1.ElizaService/Say": Endpoint.unary(
                     method=MethodInfo(
                         name="Say",
@@ -57,7 +58,7 @@ def __init__(
                         output=example_dot_eliza__pb2.SayResponse,
                         idempotency_level=IdempotencyLevel.NO_SIDE_EFFECTS,
                     ),
-                    function=service.say,
+                    function=svc.say,
                 ),
                 "/connectrpc.eliza.v1.ElizaService/Converse": Endpoint.bidi_stream(
                     method=MethodInfo(
@@ -67,7 +68,7 @@ def __init__(
                         output=example_dot_eliza__pb2.ConverseResponse,
                         idempotency_level=IdempotencyLevel.UNKNOWN,
                     ),
-                    function=service.converse,
+                    function=svc.converse,
                 ),
                 "/connectrpc.eliza.v1.ElizaService/Introduce": Endpoint.server_stream(
                     method=MethodInfo(
@@ -77,7 +78,7 @@ def __init__(
                         output=example_dot_eliza__pb2.IntroduceResponse,
                         idempotency_level=IdempotencyLevel.UNKNOWN,
                     ),
-                    function=service.introduce,
+                    function=svc.introduce,
                 ),
             },
             interceptors=interceptors,

protoc-gen-connect-python/generator/generator_test.go

@@ -106,7 +106,7 @@ func TestGenerateConnectFile(t *testing.T) {
 				}
 
 				content := got.GetContent()
-				if !strings.Contains(content, "from collections.abc import AsyncIterator, Iterable, Iterator, Mapping") {
+				if !strings.Contains(content, "from collections.abc import AsyncGenerator, AsyncIterator, Iterable, Iterator, Mapping") {
 					t.Error("Generated code missing required imports")
 				}
 				if !strings.Contains(content, "class "+strings.Split(tt.input.GetService()[0].GetName(), ".")[0]) {

protoc-gen-connect-python/generator/template.go

@@ -44,7 +44,7 @@ var ConnectTemplate = template.Must(template.New("ConnectTemplate").Parse(`# -*-
 # Generated by https://github.com/connectrpc/connect-python.  DO NOT EDIT!
 # source: {{.FileName}}
 {{if .Services}}
-from collections.abc import AsyncIterator, Iterable, Iterator, Mapping
+from collections.abc import AsyncGenerator, AsyncIterator, Iterable, Iterator, Mapping
 from typing import Protocol
 
 from connectrpc.client import ConnectClient, ConnectClientSync
@@ -67,10 +67,11 @@ class {{.Name}}(Protocol):{{- range .Methods }}
         raise ConnectError(Code.UNIMPLEMENTED, "Not implemented")
 {{ end }}
 
-class {{.Name}}ASGIApplication(ConnectASGIApplication):
-    def __init__(self, service: {{.Name}}, *, interceptors: Iterable[Interceptor]=(), read_max_bytes: int | None = None) -> None:
+class {{.Name}}ASGIApplication(ConnectASGIApplication[{{.Name}}]):
+    def __init__(self, service: {{.Name}} | AsyncGenerator[{{.Name}}], *, interceptors: Iterable[Interceptor]=(), read_max_bytes: int | None = None) -> None:
         super().__init__(
-            endpoints={ {{- range .Methods }}
+            service=service,
+            endpoints=lambda svc: { {{- range .Methods }}
                 "/{{.ServiceName}}/{{.Name}}": Endpoint.{{.EndpointType}}(
                     method=MethodInfo(
                         name="{{.Name}}",
@@ -79,7 +80,7 @@ class {{.Name}}ASGIApplication(ConnectASGIApplication):
                         output={{.OutputType}},
                         idempotency_level=IdempotencyLevel.{{.IdempotencyLevel}},
                     ),
-                    function=service.{{.PythonName}},
+                    function=svc.{{.PythonName}},
                 ),{{- end }}
             },
             interceptors=interceptors,

protoc-gen-connect-python/generator/template_test.go

@@ -36,9 +36,9 @@ func TestConnectTemplate(t *testing.T) {
 				},
 			},
 			contains: []string{
-				"from collections.abc import AsyncIterator, Iterable, Iterator, Mapping",
+				"from collections.abc import AsyncGenerator, AsyncIterator, Iterable, Iterator, Mapping",
 				"class TestService(Protocol):",
-				"class TestServiceASGIApplication(ConnectASGIApplication):",
+				"class TestServiceASGIApplication(ConnectASGIApplication[TestService]):",
 				"def TestMethod",
 			},
 		},

src/connectrpc/_server_async.py

@@ -1,11 +1,19 @@
 import base64
 import functools
-from abc import ABC, abstractmethod
+import inspect
+from abc import abstractmethod
 from asyncio import CancelledError, sleep
-from collections.abc import AsyncIterator, Iterable, Mapping, Sequence
+from collections.abc import (
+    AsyncGenerator,
+    AsyncIterator,
+    Callable,
+    Iterable,
+    Mapping,
+    Sequence,
+)
 from dataclasses import replace
 from http import HTTPStatus
-from typing import TYPE_CHECKING, TypeVar
+from typing import TYPE_CHECKING, Generic, TypeVar, cast
 from urllib.parse import parse_qs
 
 from . import _compression, _server_shared
@@ -48,6 +56,7 @@
     Scope = "asgiref.typing.Scope"
 
 
+_SVC = TypeVar("_SVC")
 _REQ = TypeVar("_REQ")
 _RES = TypeVar("_RES")
 
@@ -64,45 +73,96 @@
 )
 
 
-class ConnectASGIApplication(ABC):
+class ConnectASGIApplication(Generic[_SVC]):
     """An ASGI application for the Connect protocol."""
 
+    _resolved_endpoints: Mapping[str, Endpoint] | None
+
     @property
     @abstractmethod
     def path(self) -> str: ...
 
     def __init__(
         self,
         *,
-        endpoints: Mapping[str, Endpoint],
+        service: _SVC | AsyncGenerator[_SVC],
+        endpoints: Callable[[_SVC], Mapping[str, Endpoint]],
         interceptors: Iterable[Interceptor] = (),
         read_max_bytes: int | None = None,
     ) -> None:
         """Initialize the ASGI application."""
         super().__init__()
-        if interceptors:
-            interceptors = resolve_interceptors(interceptors)
-            endpoints = {
-                path: _apply_interceptors(endpoint, interceptors)
-                for path, endpoint in endpoints.items()
-            }
+        self._service = service
         self._endpoints = endpoints
+        self._interceptors = interceptors
+        self._resolved_endpoints = None
         self._read_max_bytes = read_max_bytes
 
     async def __call__(
         self, scope: Scope, receive: ASGIReceiveCallable, send: ASGISendCallable
     ) -> None:
-        assert scope["type"] == "http"  # noqa: S101 - only for type narrowing, in practice always true
+        if scope["type"] == "websocket":
+            msg = "connect does not support websockets"
+            raise RuntimeError(msg)
+
+        if scope["type"] == "lifespan":
+            service_iter = None
+            while True:
+                msg = await receive()
+                match msg["type"]:
+                    case "lifespan.startup":
+                        # Need to cast since type checking doesn't seem to narrow well with isasyncgen
+                        if inspect.isasyncgen(self._service):
+                            service_iter = cast(
+                                "AsyncGenerator[_SVC, None]", self._service
+                            )
+                            try:
+                                service = await anext(service_iter)
+                            except Exception as e:
+                                await send(
+                                    {
+                                        "type": "lifespan.startup.failed",
+                                        "message": str(e),
+                                    }
+                                )
+                                return None
+                        else:
+                            service = cast("_SVC", self._service)
+                        self._resolved_endpoints = self._resolve_endpoints(service)
+                        await send({"type": "lifespan.startup.complete"})
+                    case "lifespan.shutdown":
+                        if service_iter is not None:
+                            try:
+                                await service_iter.aclose()
+                            except Exception as e:
+                                await send(
+                                    {
+                                        "type": "lifespan.shutdown.failed",
+                                        "message": str(e),
+                                    }
+                                )
+                                return None
+                        await send({"type": "lifespan.shutdown.complete"})
+                        return None
+
+        if not self._resolved_endpoints:
+            if inspect.isasyncgen(self._service):
+                msg = "ASGI server does not support lifespan but async generator passed for service. Enable lifespan support."
+                raise RuntimeError(msg)
+
+            self._resolved_endpoints = self._resolve_endpoints(
+                cast("_SVC", self._service)
+            )
+        endpoints = self._resolved_endpoints
 
         ctx: RequestContext | None = None
         try:
             path = scope["path"]
-            endpoint = self._endpoints.get(path)
+            endpoint = endpoints.get(path)
             if not endpoint and scope["root_path"]:
                 # The application was mounted at some root so try stripping the prefix.
                 path = path.removeprefix(scope["root_path"])
-                endpoint = self._endpoints.get(path)
-
+                endpoint = endpoints.get(path)
             if not endpoint:
                 raise HTTPException(HTTPStatus.NOT_FOUND, [])
 
@@ -381,6 +441,17 @@ async def _handle_error(
         )
         await send({"type": "http.response.body", "body": body, "more_body": False})
 
+    def _resolve_endpoints(self, service: _SVC) -> Mapping[str, Endpoint]:
+        resolved_endpoints = self._endpoints(service)
+        if self._interceptors:
+            resolved_endpoints = {
+                path: _apply_interceptors(
+                    endpoint, resolve_interceptors(self._interceptors)
+                )
+                for path, endpoint in resolved_endpoints.items()
+            }
+        return resolved_endpoints
+
 
 async def _send_stream_response_headers(
     send: ASGISendCallable, codec: Codec, compression_name: str, ctx: RequestContext