feat(ext/http): Add support for trailers w/internal API (HTTP/2 only) (#19182)

Necessary for #3326. 

Requested in #10214 as well.

6 files changed, 103 insertions, 2 deletions

diff --git a/cli/tests/unit/serve_test.ts b/cli/tests/unit/serve_test.ts
index c6cfc45f3..0f97e17b8 100644
--- a/cli/tests/unit/serve_test.ts
+++ b/cli/tests/unit/serve_test.ts
@@ -15,6 +15,7 @@ import {
 
 const {
   upgradeHttpRaw,
+  addTrailers,
   // @ts-expect-error TypeScript (as of 3.7) does not support indexing namespaces by symbol
 } = Deno[Deno.internal];
 
@@ -2903,6 +2904,45 @@ Deno.test(
   },
 );
 
+// TODO(mmastrac): This test should eventually use fetch, when we support trailers there.
+// This test is ignored because it's flaky and relies on cURL's verbose output.
+Deno.test(
+  { permissions: { net: true, run: true, read: true }, ignore: true },
+  async function httpServerTrailers() {
+    const ac = new AbortController();
+    const listeningPromise = deferred();
+
+    const server = Deno.serve({
+      handler: () => {
+        const response = new Response("Hello World", {
+          headers: {
+            "trailer": "baz",
+            "transfer-encoding": "chunked",
+            "foo": "bar",
+          },
+        });
+        addTrailers(response, [["baz", "why"]]);
+        return response;
+      },
+      port: 4501,
+      signal: ac.signal,
+      onListen: onListen(listeningPromise),
+      onError: createOnErrorCb(ac),
+    });
+
+    // We don't have a great way to access this right now, so just fetch the trailers with cURL
+    const [_, stderr] = await curlRequestWithStdErr([
+      "http://localhost:4501/path",
+      "-v",
+      "--http2",
+      "--http2-prior-knowledge",
+    ]);
+    assertMatch(stderr, /baz: why/);
+    ac.abort();
+    await server;
+  },
+);
+
 Deno.test(
   { permissions: { net: true, run: true, read: true } },
   async function httpsServeCurlH2C() {
@@ -2948,3 +2988,13 @@ async function curlRequest(args: string[]) {
   assert(success);
   return new TextDecoder().decode(stdout);
 }
+
+async function curlRequestWithStdErr(args: string[]) {
+  const { success, stdout, stderr } = await new Deno.Command("curl", {
+    args,
+    stdout: "piped",
+    stderr: "piped",
+  }).output();
+  assert(success);
+  return [new TextDecoder().decode(stdout), new TextDecoder().decode(stderr)];
+}
diff --git a/ext/http/00_serve.js b/ext/http/00_serve.js
index 9075ae651..7186da1fe 100644
--- a/ext/http/00_serve.js
+++ b/ext/http/00_serve.js
@@ -60,6 +60,7 @@ const {
   op_http_set_response_body_text,
   op_http_set_response_header,
   op_http_set_response_headers,
+  op_http_set_response_trailers,
   op_http_upgrade_raw,
   op_http_upgrade_websocket_next,
   op_http_wait,
@@ -75,6 +76,7 @@ const {
   "op_http_set_response_body_text",
   "op_http_set_response_header",
   "op_http_set_response_headers",
+  "op_http_set_response_trailers",
   "op_http_upgrade_raw",
   "op_http_upgrade_websocket_next",
   "op_http_wait",
@@ -125,6 +127,11 @@ function upgradeHttpRaw(req, conn) {
   throw new TypeError("upgradeHttpRaw may only be used with Deno.serve");
 }
 
+function addTrailers(resp, headerList) {
+  const inner = toInnerResponse(resp);
+  op_http_set_response_trailers(inner.slabId, headerList);
+}
+
 class InnerRequest {
   #slabId;
   #context;
@@ -687,6 +694,7 @@ function serve(arg1, arg2) {
   return { finished };
 }
 
+internals.addTrailers = addTrailers;
 internals.upgradeHttpRaw = upgradeHttpRaw;
 
 export { serve, upgradeHttpRaw };
diff --git a/ext/http/http_next.rs b/ext/http/http_next.rs
index 34281ee92..30a8c9d51 100644
--- a/ext/http/http_next.rs
+++ b/ext/http/http_next.rs
@@ -318,6 +318,22 @@ pub fn op_http_set_response_headers(
   }
 }
 
+#[op]
+pub fn op_http_set_response_trailers(
+  slab_id: SlabId,
+  trailers: Vec<(ByteString, ByteString)>,
+) {
+  let mut http = slab_get(slab_id);
+  let mut trailer_map: HeaderMap = HeaderMap::with_capacity(trailers.len());
+  for (name, value) in trailers {
+    // These are valid latin-1 strings
+    let name = HeaderName::from_bytes(&name).unwrap();
+    let value = HeaderValue::from_bytes(&value).unwrap();
+    trailer_map.append(name, value);
+  }
+  *http.trailers().borrow_mut() = Some(trailer_map);
+}
+
 fn is_request_compressible(headers: &HeaderMap) -> Compression {
   let Some(accept_encoding) = headers.get(ACCEPT_ENCODING) else {
     return Compression::None;
diff --git a/ext/http/lib.rs b/ext/http/lib.rs
index 2660f4653..7d37c53e1 100644
--- a/ext/http/lib.rs
+++ b/ext/http/lib.rs
@@ -116,6 +116,7 @@ deno_core::extension!(
     http_next::op_http_set_response_body_text,
     http_next::op_http_set_response_header,
     http_next::op_http_set_response_headers,
+    http_next::op_http_set_response_trailers,
     http_next::op_http_track,
     http_next::op_http_upgrade_websocket_next,
     http_next::op_http_upgrade_raw,
diff --git a/ext/http/response_body.rs b/ext/http/response_body.rs
index e30c917c3..ea6cc5ab8 100644
--- a/ext/http/response_body.rs
+++ b/ext/http/response_body.rs
@@ -158,7 +158,11 @@ impl std::fmt::Debug for ResponseBytesInner {
 /// required by hyper. As the API requires information about request completion (including a success/fail
 /// flag), we include a very lightweight [`CompletionHandle`] for interested parties to listen on.
 #[derive(Debug, Default)]
-pub struct ResponseBytes(ResponseBytesInner, CompletionHandle);
+pub struct ResponseBytes(
+  ResponseBytesInner,
+  CompletionHandle,
+  Rc<RefCell<Option<HeaderMap>>>,
+);
 
 impl ResponseBytes {
   pub fn initialize(&mut self, inner: ResponseBytesInner) {
@@ -170,6 +174,10 @@ impl ResponseBytes {
     self.1.clone()
   }
 
+  pub fn trailers(&self) -> Rc<RefCell<Option<HeaderMap>>> {
+    self.2.clone()
+  }
+
   fn complete(&mut self, success: bool) -> ResponseBytesInner {
     if matches!(self.0, ResponseBytesInner::Done) {
       return ResponseBytesInner::Done;
@@ -250,6 +258,9 @@ impl Body for ResponseBytes {
     let res = loop {
       let res = match &mut self.0 {
         ResponseBytesInner::Done | ResponseBytesInner::Empty => {
+          if let Some(trailers) = self.2.borrow_mut().take() {
+            return std::task::Poll::Ready(Some(Ok(Frame::trailers(trailers))));
+          }
           unreachable!()
         }
         ResponseBytesInner::Bytes(..) => {
@@ -271,6 +282,9 @@ impl Body for ResponseBytes {
     };
 
     if matches!(res, ResponseStreamResult::EndOfStream) {
+      if let Some(trailers) = self.2.borrow_mut().take() {
+        return std::task::Poll::Ready(Some(Ok(Frame::trailers(trailers))));
+      }
       self.complete(true);
     }
     std::task::Poll::Ready(res.into())
@@ -278,6 +292,7 @@ impl Body for ResponseBytes {
 
   fn is_end_stream(&self) -> bool {
     matches!(self.0, ResponseBytesInner::Done | ResponseBytesInner::Empty)
+      && self.2.borrow_mut().is_none()
   }
 
   fn size_hint(&self) -> SizeHint {
diff --git a/ext/http/slab.rs b/ext/http/slab.rs
index 24554d689..93a56e9ff 100644
--- a/ext/http/slab.rs
+++ b/ext/http/slab.rs
@@ -4,6 +4,7 @@ use crate::response_body::CompletionHandle;
 use crate::response_body::ResponseBytes;
 use deno_core::error::AnyError;
 use http::request::Parts;
+use http::HeaderMap;
 use hyper1::body::Incoming;
 use hyper1::upgrade::OnUpgrade;
 
@@ -11,6 +12,7 @@ use slab::Slab;
 use std::cell::RefCell;
 use std::cell::RefMut;
 use std::ptr::NonNull;
+use std::rc::Rc;
 
 pub type Request = hyper1::Request<Incoming>;
 pub type Response = hyper1::Response<ResponseBytes>;
@@ -23,6 +25,7 @@ pub struct HttpSlabRecord {
   // The response may get taken before we tear this down
   response: Option<Response>,
   promise: CompletionHandle,
+  trailers: Rc<RefCell<Option<HeaderMap>>>,
   been_dropped: bool,
   #[cfg(feature = "__zombie_http_tracking")]
   alive: bool,
@@ -81,11 +84,14 @@ fn slab_insert_raw(
 ) -> SlabId {
   let index = SLAB.with(|slab| {
     let mut slab = slab.borrow_mut();
+    let body = ResponseBytes::default();
+    let trailers = body.trailers();
     slab.insert(HttpSlabRecord {
       request_info,
       request_parts,
       request_body,
-      response: Some(Response::new(ResponseBytes::default())),
+      response: Some(Response::new(body)),
+      trailers,
       been_dropped: false,
       promise: CompletionHandle::default(),
       #[cfg(feature = "__zombie_http_tracking")]
@@ -182,6 +188,11 @@ impl SlabEntry {
     self.self_mut().response.as_mut().unwrap()
   }
 
+  /// Get a mutable reference to the trailers.
+  pub fn trailers(&mut self) -> &RefCell<Option<HeaderMap>> {
+    &self.self_mut().trailers
+  }
+
   /// Take the response.
   pub fn take_response(&mut self) -> Response {
     self.self_mut().response.take().unwrap()