h2/h3 trailing header support. Fixes #147

src/hypercorn/protocol/events.py

@@ -27,6 +27,11 @@ class EndBody(Event):
     pass
 
 
+@dataclass(frozen=True)
+class Trailers(Event):
+    headers: List[Tuple[bytes, bytes]]
+
+
 @dataclass(frozen=True)
 class Data(Event):
     data: bytes

src/hypercorn/protocol/h2.py

@@ -18,6 +18,7 @@
     Request,
     Response,
     StreamClosed,
+    Trailers,
 )
 from .http_stream import HTTPStream
 from .ws_stream import WSStream
@@ -212,6 +213,9 @@ async def stream_send(self, event: StreamEvent) -> None:
                 self.priority.unblock(event.stream_id)
                 await self.has_data.set()
                 await self.stream_buffers[event.stream_id].drain()
+            elif isinstance(event, Trailers):
+                self.connection.send_headers(event.stream_id, event.headers)
+                await self._flush()
             elif isinstance(event, StreamClosed):
                 await self._close_stream(event.stream_id)
                 idle = len(self.streams) == 0 or all(

src/hypercorn/protocol/h3.py

@@ -18,6 +18,7 @@
     Request,
     Response,
     StreamClosed,
+    Trailers,
 )
 from .http_stream import HTTPStream
 from .ws_stream import WSStream
@@ -79,6 +80,9 @@ async def stream_send(self, event: StreamEvent) -> None:
         elif isinstance(event, (EndBody, EndData)):
             self.connection.send_data(event.stream_id, b"", True)
             await self.send()
+        elif isinstance(event, Trailers):
+            self.connection.send_headers(event.stream_id, event.headers)
+            await self.send()
         elif isinstance(event, StreamClosed):
             pass  # ??
         elif isinstance(event, Request):

src/hypercorn/protocol/http_stream.py

@@ -5,7 +5,16 @@
 from typing import Awaitable, Callable, Optional, Tuple
 from urllib.parse import unquote
 
-from .events import Body, EndBody, Event, InformationalResponse, Request, Response, StreamClosed
+from .events import (
+    Body,
+    EndBody,
+    Event,
+    InformationalResponse,
+    Request,
+    Response,
+    StreamClosed,
+    Trailers,
+)
 from ..config import Config
 from ..typing import (
     AppWrapper,
@@ -22,6 +31,7 @@
     valid_server_name,
 )
 
+TRAILERS_VERSIONS = {"2", "3"}
 PUSH_VERSIONS = {"2", "3"}
 EARLY_HINTS_VERSIONS = {"2", "3"}
 
@@ -88,6 +98,10 @@ async def handle(self, event: Event) -> None:
                 "server": self.server,
                 "extensions": {},
             }
+
+            if event.http_version in TRAILERS_VERSIONS:
+                self.scope["extensions"]["http.response.trailers"] = {}
+
             if event.http_version in PUSH_VERSIONS:
                 self.scope["extensions"]["http.response.push"] = {}
 
@@ -181,13 +195,43 @@ async def app_send(self, message: Optional[ASGISendEvent]) -> None:
                     )
 
                 if not message.get("more_body", False):
-                    if self.state != ASGIHTTPState.CLOSED:
+                    await self.send(EndBody(stream_id=self.stream_id))
+
+                    if not self.response.get("trailers", False):
                         self.state = ASGIHTTPState.CLOSED
                         await self.config.log.access(
                             self.scope, self.response, time() - self.start_time
                         )
-                        await self.send(EndBody(stream_id=self.stream_id))
                         await self.send(StreamClosed(stream_id=self.stream_id))
+            elif (
+                message["type"] == "http.response.trailers"
+                and self.scope["http_version"] in TRAILERS_VERSIONS
+                and self.state
+                in {
+                    ASGIHTTPState.REQUEST,
+                    ASGIHTTPState.RESPONSE,
+                }
+            ):
+                if self.state == ASGIHTTPState.REQUEST:
+                    headers = build_and_validate_headers(self.response.get("headers", []))
+                    await self.send(
+                        Response(
+                            stream_id=self.stream_id,
+                            headers=headers,
+                            status_code=int(self.response["status"]),
+                        )
+                    )
+                    self.state = ASGIHTTPState.RESPONSE
+
+                headers = build_and_validate_headers(message["headers"])
+                await self.send(Trailers(stream_id=self.stream_id, headers=headers))
+
+                if not message.get("more_trailers", False):
+                    self.state = ASGIHTTPState.CLOSED
+                    await self.config.log.access(
+                        self.scope, self.response, time() - self.start_time
+                    )
+                    await self.send(StreamClosed(stream_id=self.stream_id))
             else:
                 raise UnexpectedMessageError(self.state, message["type"])
 

src/hypercorn/typing.py

@@ -83,6 +83,7 @@ class HTTPResponseStartEvent(TypedDict):
     type: Literal["http.response.start"]
     status: int
     headers: Iterable[Tuple[bytes, bytes]]
+    trailers: Optional[bool]
 
 
 class HTTPResponseBodyEvent(TypedDict):
@@ -91,6 +92,12 @@ class HTTPResponseBodyEvent(TypedDict):
     more_body: bool
 
 
+class HTTPResponseTrailersEvent(TypedDict):
+    type: Literal["http.response.trailers"]
+    headers: Iterable[Tuple[bytes, bytes]]
+    more_trailers: bool
+
+
 class HTTPServerPushEvent(TypedDict):
     type: Literal["http.response.push"]
     path: str
@@ -191,6 +198,7 @@ class LifespanShutdownFailedEvent(TypedDict):
 ASGISendEvent = Union[
     HTTPResponseStartEvent,
     HTTPResponseBodyEvent,
+    HTTPResponseTrailersEvent,
     HTTPServerPushEvent,
     HTTPEarlyHintEvent,
     HTTPDisconnectEvent,

tests/protocol/test_http_stream.py

@@ -83,7 +83,11 @@ async def test_handle_request_http_2(stream: HTTPStream) -> None:
         "headers": [],
         "client": None,
         "server": None,
-        "extensions": {"http.response.early_hint": {}, "http.response.push": {}},
+        "extensions": {
+            "http.response.trailers": {},
+            "http.response.early_hint": {},
+            "http.response.push": {},
+        },
     }