http2: preserve multiple content-encoding values

Remove content-encoding from the single-value field set so incoming
values are joined in order and outgoing arrays are accepted.

Update the header documentation and add coverage for requests and
responses, including repeated codings and strict validation options.

For repeated fields, the incoming value now includes every coding
instead of only the first. Outgoing arrays no longer throw
ERR_HTTP2_HEADER_SINGLE_VALUE by default.

Fixes: #67151
Assisted-by: Codex
Signed-off-by: inoway46 <inoueyuya416@gmail.com>
PR-URL: #67184
Reviewed-By: Tim Perry <pimterry@gmail.com>

Author: inoway46

doc/api/http2.md

@@ -3722,7 +3722,7 @@ For incoming headers:
 * The `:status` header is converted to `number`.
 * Duplicates of `:status`, `:method`, `:authority`, `:scheme`, `:path`,
   `:protocol`, `age`, `authorization`, `access-control-allow-credentials`,
-  `access-control-max-age`, `access-control-request-method`, `content-encoding`,
+  `access-control-max-age`, `access-control-request-method`,
   `content-language`, `content-length`, `content-location`, `content-md5`,
   `content-range`, `content-type`, `date`, `dnt`, `etag`, `expires`, `from`,
   `host`, `if-match`, `if-modified-since`, `if-none-match`, `if-range`,

lib/internal/http2/util.js

@@ -64,7 +64,6 @@ const {
   HTTP2_HEADER_ACCESS_CONTROL_REQUEST_METHOD,
   HTTP2_HEADER_AGE,
   HTTP2_HEADER_AUTHORIZATION,
-  HTTP2_HEADER_CONTENT_ENCODING,
   HTTP2_HEADER_CONTENT_LANGUAGE,
   HTTP2_HEADER_CONTENT_LENGTH,
   HTTP2_HEADER_CONTENT_LOCATION,
@@ -136,7 +135,6 @@ const kSingleValueFields = new SafeSet([
   HTTP2_HEADER_ACCESS_CONTROL_REQUEST_METHOD,
   HTTP2_HEADER_AGE,
   HTTP2_HEADER_AUTHORIZATION,
-  HTTP2_HEADER_CONTENT_ENCODING,
   HTTP2_HEADER_CONTENT_LANGUAGE,
   HTTP2_HEADER_CONTENT_LENGTH,
   HTTP2_HEADER_CONTENT_LOCATION,

test/parallel/test-http2-content-encoding.js

@@ -0,0 +1,57 @@
+'use strict';
+
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+const assert = require('node:assert/strict');
+const http2 = require('node:http2');
+const { once } = require('node:events');
+
+// Content-Encoding is a list (RFC 9110 section 8.4). Preserve all codings
+// in their original order, regardless of single-value field validation.
+async function test(options, value) {
+  const values = Array.isArray(value) ? value : [value];
+  const expectedRaw = values.flatMap((v) => ['content-encoding', v]);
+  const expected = values.join(', ');
+
+  function check(headers, rawHeaders) {
+    assert.strictEqual(headers['content-encoding'], expected);
+    const raw = [];
+    for (let i = 0; i < rawHeaders.length; i += 2) {
+      if (rawHeaders[i] === 'content-encoding')
+        raw.push(rawHeaders[i], rawHeaders[i + 1]);
+    }
+    assert.deepStrictEqual(raw, expectedRaw);
+  }
+
+  const server = http2.createServer(options);
+  server.on('stream', common.mustCall((stream, headers, flags, rawHeaders) => {
+    check(headers, rawHeaders);
+    stream.respond({ 'content-encoding': value });
+    stream.end();
+  }));
+  server.listen(0);
+  await once(server, 'listening');
+
+  const client = http2.connect(`http://localhost:${server.address().port}`, options);
+  const req = client.request({ 'content-encoding': value });
+  req.on('response', common.mustCall((headers, flags, rawHeaders) => {
+    check(headers, rawHeaders);
+  }));
+  req.resume();
+  req.end();
+  await once(req, 'end');
+  client.close();
+  await once(client, 'close');
+  await new Promise((resolve) => server.close(resolve));
+}
+
+(async () => {
+  for (const options of [{}, { strictSingleValueFields: true },
+                         { strictSingleValueFields: false }]) {
+    for (const value of ['gzip', 'gzip, br', ['gzip', 'br'],
+                         ['br', 'gzip'], ['gzip', 'gzip']]) {
+      await test(options, value);
+    }
+  }
+})().then(common.mustCall());

test/parallel/test-http2-util-headers-list.js

@@ -219,7 +219,6 @@ const {
   HTTP2_HEADER_ACCESS_CONTROL_REQUEST_METHOD,
   HTTP2_HEADER_AGE,
   HTTP2_HEADER_AUTHORIZATION,
-  HTTP2_HEADER_CONTENT_ENCODING,
   HTTP2_HEADER_CONTENT_LANGUAGE,
   HTTP2_HEADER_CONTENT_LENGTH,
   HTTP2_HEADER_CONTENT_LOCATION,
@@ -267,6 +266,7 @@ const {
 });
 
 [
+  HTTP2_HEADER_CONTENT_ENCODING,
   HTTP2_HEADER_ACCEPT_CHARSET,
   HTTP2_HEADER_ACCEPT_ENCODING,
   HTTP2_HEADER_ACCEPT_LANGUAGE,
@@ -419,3 +419,10 @@ assert.strictEqual(getAuthority({
   assert.strictEqual(headers.age, '10');
   assert.strictEqual(headers['x-multi'], 'first, second');
 }
+
+// Content-Encoding is an ordered list, including repeated content codings.
+for (const values of [['gzip', 'br'], ['br', 'gzip'], ['gzip', 'gzip']]) {
+  const rawHeaders = values.flatMap((value) => ['content-encoding', value]);
+  assert.strictEqual(toHeaderObject(rawHeaders)['content-encoding'],
+                     values.join(', '));
+}