http2: remember sent headers

Add sentHeaders, sentTrailers, and sentInfoHeaders properties
on `Http2Stream`.

Fixes: #16619

doc/api/http2.md

@@ -989,6 +989,34 @@ destroyed after either receiving an `RST_STREAM` frame from the connected peer,
 calling `http2stream.close()`, or `http2stream.destroy()`. Will be
 `undefined` if the `Http2Stream` has not been closed.
 
+#### http2stream.sentHeaders
+<!-- YAML
+added: REPLACEME
+-->
+
+* Value: {[Headers Object][]}
+
+An object containing the outbound headers sent for this `Http2Stream`.
+
+#### http2stream.sentInfoHeaders
+<!-- YAML
+added: REPLACEME
+-->
+
+* Value: {[Headers Object][]\[\]}
+
+An array of objects containing the outbound informational (additional) headers
+sent for this `Http2Stream`.
+
+#### http2stream.sentTrailers
+<!-- YAML
+added: REPLACEME
+-->
+
+* Value: {[Headers Object][]}
+
+An object containing the outbound trailers sent for this this `HttpStream`.
+
 #### http2stream.session
 <!-- YAML
 added: v8.4.0

lib/internal/http2/core.js

@@ -76,6 +76,7 @@ const kEncrypted = Symbol('encrypted');
 const kHandle = Symbol('handle');
 const kID = Symbol('id');
 const kInit = Symbol('init');
+const kInfoHeaders = Symbol('sent-info-headers');
 const kMaybeDestroy = Symbol('maybe-destroy');
 const kLocalSettings = Symbol('local-settings');
 const kOptions = Symbol('options');
@@ -84,6 +85,8 @@ const kProceed = Symbol('proceed');
 const kProtocol = Symbol('protocol');
 const kProxySocket = Symbol('proxy-socket');
 const kRemoteSettings = Symbol('remote-settings');
+const kSentHeaders = Symbol('sent-headers');
+const kSentTrailers = Symbol('sent-trailers');
 const kServer = Symbol('server');
 const kSession = Symbol('session');
 const kState = Symbol('state');
@@ -258,6 +261,7 @@ function onStreamTrailers() {
     stream.destroy(headersList);
     return [];
   }
+  stream[kSentTrailers] = trailers;
   return headersList;
 }
 
@@ -1348,6 +1352,7 @@ class ClientHttp2Session extends Http2Session {
       throw headersList;
 
     const stream = new ClientHttp2Stream(this, undefined, undefined, {});
+    stream[kSentHeaders] = headers;
 
     // Close the writable side of the stream if options.endStream is set.
     if (options.endStream)
@@ -1514,6 +1519,18 @@ class Http2Stream extends Duplex {
     return `Http2Stream ${util.format(obj)}`;
   }
 
+  get sentHeaders() {
+    return this[kSentHeaders];
+  }
+
+  get sentTrailers() {
+    return this[kSentTrailers];
+  }
+
+  get sentInfoHeaders() {
+    return this[kInfoHeaders];
+  }
+
   get pending() {
     return this[kID] === undefined;
   }
@@ -1855,6 +1872,7 @@ function processRespondWithFD(self, fd, headers, offset = 0, length = -1,
   state.flags |= STREAM_FLAGS_HEADERS_SENT;
 
   const headersList = mapToHeaders(headers, assertValidPseudoHeaderResponse);
+  self[kSentHeaders] = headers;
   if (!Array.isArray(headersList)) {
     self.destroy(headersList);
     return;
@@ -2085,6 +2103,7 @@ class ServerHttp2Stream extends Http2Stream {
 
     const id = ret.id();
     const stream = new ServerHttp2Stream(session, ret, id, options, headers);
+    stream[kSentHeaders] = headers;
 
     if (options.endStream)
       stream.end();
@@ -2144,6 +2163,7 @@ class ServerHttp2Stream extends Http2Stream {
     const headersList = mapToHeaders(headers, assertValidPseudoHeaderResponse);
     if (!Array.isArray(headersList))
       throw headersList;
+    this[kSentHeaders] = headers;
 
     state.flags |= STREAM_FLAGS_HEADERS_SENT;
 
@@ -2329,6 +2349,10 @@ class ServerHttp2Stream extends Http2Stream {
     const headersList = mapToHeaders(headers, assertValidPseudoHeaderResponse);
     if (!Array.isArray(headersList))
       throw headersList;
+    if (!this[kInfoHeaders])
+      this[kInfoHeaders] = [headers];
+    else
+      this[kInfoHeaders].push(headers);
 
     const ret = this[kHandle].info(headersList);
     if (ret < 0)

test/parallel/test-http2-sent-headers.js

@@ -0,0 +1,47 @@
+'use strict';
+
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+const assert = require('assert');
+const h2 = require('http2');
+
+const server = h2.createServer();
+
+server.on('stream', common.mustCall((stream) => {
+  stream.additionalHeaders({ ':status': 102 });
+  assert.strictEqual(stream.sentInfoHeaders[0][':status'], 102);
+
+  stream.respond({ abc: 'xyz' }, {
+    getTrailers(headers) {
+      headers.xyz = 'abc';
+    }
+  });
+  assert.strictEqual(stream.sentHeaders.abc, 'xyz');
+  assert.strictEqual(stream.sentHeaders[':status'], 200);
+  assert.notStrictEqual(stream.sentHeaders.date, undefined);
+  stream.end();
+  stream.on('close', () => {
+    assert.strictEqual(stream.sentTrailers.xyz, 'abc');
+  });
+}));
+
+server.listen(0, common.mustCall(() => {
+  const client = h2.connect(`http://localhost:${server.address().port}`);
+  const req = client.request();
+
+  req.on('headers', common.mustCall((headers) => {
+    assert.strictEqual(headers[':status'], 102);
+  }));
+
+  assert.strictEqual(req.sentHeaders[':method'], 'GET');
+  assert.strictEqual(req.sentHeaders[':authority'],
+                     `localhost:${server.address().port}`);
+  assert.strictEqual(req.sentHeaders[':scheme'], 'http');
+  assert.strictEqual(req.sentHeaders[':path'], '/');
+  req.resume();
+  req.on('close', () => {
+    server.close();
+    client.close();
+  });
+}));