Use the frame Accept header for prefetches.

noamr · chromium-wpt-export-bot · commit b95560e8d71f · 2022-12-12T23:21:08.000-08:00
Special-casing prefetches makes it so that `Vary: Accept` makes the browser erroneously reject the prefetched response. Also changed the SXG ?q= value for the frame accept header, as it was done for prefetch (and should have been done for the frame accept header). For now CORS prefetches remain untouched, as changing them to the >128bytes frame accept headers would cause incompatibility due to a CORS-preflight requirement. This was previously unspecified, See whatwg/fetch#1485 Bug: 626081 Change-Id: I2c99f4f1abd2556fdf456d877588b346a22fd677
diff --git a/preload/prefetch-accept.html b/preload/prefetch-accept.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<title>Ensures that prefetch works with documents</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/utils.js"></script>
+<script src="/common/dispatcher/dispatcher.js"></script>
+<script src="resources/prefetch-helper.js"></script>
+<body>
+<script>
+
+promise_test(async t => {
+    const {href, uid} = await prefetch({
+        file: "prefetch-exec.html",
+        type: "text/html",
+        origin: document.origin});
+    const popup = window.open(href + "&cache_bust=" + token());
+    const remoteContext = new RemoteContext(uid);
+    t.add_cleanup(() => popup.close());
+    await remoteContext.execute_script(() => "OK");
+    const results = await get_prefetch_info(href);
+    assert_equals(results.length, 2);
+    assert_equals(results[0].headers.accept, results[1].headers.accept);
+}, "Document prefetch should send the exact Accept header as navigation")
+
+</script>
+</body>
diff --git a/preload/resources/prefetch-exec.html b/preload/resources/prefetch-exec.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>Message BC</title>
+<script src="/common/dispatcher/dispatcher.js"></script>
+<script>
+"use strict";
+const params = new URLSearchParams(location.search);
+window.executor = new Executor(params.get("key"));
+</script>
diff --git a/preload/resources/prefetch-helper.js b/preload/resources/prefetch-helper.js
@@ -0,0 +1,23 @@
+async function get_prefetch_info(href) {
+    const response = await fetch(`${href}&mode=info`, {mode: "cors"});
+    return await response.json();
+}
+
+async function prefetch(p = {}, t) {
+    const link = document.createElement("link");
+    link.rel = "prefetch";
+    link.as = p.as;
+    if (p.crossOrigin)
+        link.setAttribute("crossorigin", p.crossOrigin);
+    const uid = token();
+    const params = new URLSearchParams();
+    params.set("key", uid);
+    for (const key in p)
+        params.set(key, p[key]);
+    const origin = p.origin || '';
+    link.href = `${origin}/preload/resources/prefetch-info.py?${params.toString()}`;
+    document.head.appendChild(link);
+    while (!(await get_prefetch_info(link.href)).length) { }
+    return {href: link.href, uid};
+}
+
diff --git a/preload/resources/prefetch-info.py b/preload/resources/prefetch-info.py
@@ -0,0 +1,37 @@
+import os
+from wptserve.utils import isomorphic_encode
+from json import dumps, loads
+
+def main(request, response):
+    key = request.GET.first(b"key").decode("utf8")
+    mode = request.GET.first(b"mode", "content")
+    status = int(request.GET.first(b"status", b"200"))
+    stash = request.server.stash
+    cors = request.GET.first(b"cors", "true")
+    if cors == "true" or mode == b"info":
+        response.headers.set(b"Access-Control-Allow-Origin", b"*")
+
+    response.status = status
+    with stash.lock:
+        requests = loads(stash.take(key) or '[]')
+        if mode == b"info":
+            response.headers.set(b"Content-Type", "application/json")
+            json_reqs = dumps(requests)
+            response.content = json_reqs
+            stash.put(key, json_reqs)
+            return
+        else:
+            headers = {}
+            for header in request.headers:
+                headers[header.decode("utf8")] = request.headers[header].decode("utf8")
+            path = request.url
+            requests.append({"headers": headers, "url": request.url})
+            stash.put(key, dumps(requests))
+
+    response.headers.set(b"Content-Type", request.GET.first(b"type", "text/plain"))
+    response.headers.set(b"Cache-Control", request.GET.first(b"cache-control", b"max-age: 604800"))
+    if b"file" in request.GET:
+        path = os.path.join(os.path.dirname(isomorphic_encode(__file__)), request.GET.first(b"file"));
+        response.content = open(path, mode=u'rb').read()
+    else:
+        return request.GET.first(b"content", "123")
