Use the frame Accept header for prefetches.

Special-casing prefetches makes it so that `Vary: Accept` makes the browser erroneously reject the prefetched response. This was previously unspecified, See whatwg/fetch#1485 Bug: 626081 Change-Id: I2c99f4f1abd2556fdf456d877588b346a22fd677
web-platform-tests · Dec 13, 2022 · 6dfeba4 · 6dfeba4
1 parent c29a034
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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")