Bug 1555927 - Cache 204 response r=mayhemer

Differential Revision: https://phabricator.services.mozilla.com/D35710

--HG--
extra : moz-landing-system : lando

netwerk/protocol/http/nsHttpResponseHead.cpp

@@ -711,6 +711,7 @@ bool nsHttpResponseHead::MustValidate() {
       // Success codes
     case 200:
     case 203:
+    case 204:
     case 206:
       // Cacheable redirects
     case 300:

netwerk/test/unit/test_cache_204_response.js

@@ -0,0 +1,62 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+Test if 204 response is cached.
+1. Make first http request and return a 204 response.
+2. Check if the first response is not cached.
+3. Make second http request and check if the response is cached.
+
+*/
+
+"use strict";
+
+const { HttpServer } = ChromeUtils.import("resource://testing-common/httpd.js");
+
+function test_handler(metadata, response) {
+  response.setHeader("Content-Type", "text/html", false);
+  response.setHeader("Cache-control", "max-age=9999", false);
+  response.setStatusLine(metadata.httpVersion, 204, "No Content");
+}
+
+function make_channel(url) {
+  let channel = NetUtil.newChannel({
+    uri: url,
+    loadUsingSystemPrincipal: true,
+  }).QueryInterface(Ci.nsIHttpChannel);
+  return channel;
+}
+
+async function get_response(channel, fromCache) {
+  return new Promise(resolve => {
+    channel.asyncOpen(
+      new ChannelListener((request, buffer, ctx, isFromCache) => {
+        ok(fromCache == isFromCache, `got response from cache = ${fromCache}`);
+        resolve();
+      })
+    );
+  });
+}
+
+async function stop_server(httpserver) {
+  return new Promise(resolve => {
+    httpserver.stop(resolve);
+  });
+}
+
+add_task(async function() {
+  let httpserver = new HttpServer();
+  httpserver.registerPathHandler("/testdir", test_handler);
+  httpserver.start(-1);
+  const PORT = httpserver.identity.primaryPort;
+  const URI = `http://localhost:${PORT}/testdir`;
+
+  let response;
+
+  await get_response(make_channel(URI, "GET"), false);
+  await get_response(make_channel(URI, "GET"), true);
+
+  await stop_server(httpserver);
+});

netwerk/test/unit/xpcshell.ini

@@ -457,4 +457,4 @@ run-sequentially = one http2 node proxy is used for all tests, this test is usin
 skip-if = true
 [test_head_request_no_response_body.js]
 [test_disabled_ftp.js]
-
+[test_cache_204_response.js]