From 702a18d69c4add94b7b737891e004c31415400da Mon Sep 17 00:00:00 2001
From: Hayato Ito <hayato@chromium.org>
Date: Tue, 19 Oct 2021 20:46:26 -0700
Subject: [PATCH] Introduce <script type=webbundle>

Introduce <script>-based API for subresource loading with Web Bundles.

See the design doc [1] for the motivation of switching from
<link>-based API to <script>-based API. The explainer [2] was already
updated to use <script>-based API.

This feature is guarded by `SubresourceWebBundles` flag.

We eventually drop the <link rel=webbundle> support and remove the
<link>-based API code once we can confirm <script>-based API can be
used as a replacement of <link>-based API.

This CL should be considered as the first step to switch to
<script>-based API. There are still gaps between <link>-based API and
<script>-based API, which will be addressed later [3].

This CL intentionally adds a very minimum test for <script>-based API
because there are already WPT tests for <script type=webbundle>. They
all have been marked as [ SKIP ] in TestExpectations until now. Now
some of them are passing after this CL.

We'll make the remaining tests pass in follow-up CLs, and also add
tests which are specific to <script>-based API as necessary. These
efforts should be tracked by crbug.com/1245166.

[1]: https://docs.google.com/document/d/1q_SodTcLuwya4cXt1gIRaVrkiaBfwWyPvkY1fqRKkgM/edit?usp=sharing&resourcekey=0-dqrFOGVCYsg8WRZ4RFgwuw
[2]: https://github.com/WICG/webpackage/blob/main/explainers/subresource-loading.md
[3]: https://github.com/WICG/webpackage/issues/670

Bug: 1245166
Change-Id: I5109b6e692baf10fd1d8a31a31d93176d4dc4ad2
---
 ...e-web-bundle-resource.https.tentative.html | 199 ++++++++++++++++++
 ...pt-supports-webbundle.https.tentative.html |  16 ++
 2 files changed, 215 insertions(+)
 create mode 100644 web-bundle/subresource-loading/script-reuse-web-bundle-resource.https.tentative.html
 create mode 100644 web-bundle/subresource-loading/script-supports-webbundle.https.tentative.html
diff --git a/web-bundle/subresource-loading/script-reuse-web-bundle-resource.https.tentative.html b/web-bundle/subresource-loading/script-reuse-web-bundle-resource.https.tentative.html
new file mode 100644
index 00000000000000..e07ee7bbbd406b
--- /dev/null
+++ b/web-bundle/subresource-loading/script-reuse-web-bundle-resource.https.tentative.html
@@ -0,0 +1,199 @@
+<!DOCTYPE html>
+<title>script type="webbundle" reuses webbundle resources</title>
+<link
+  rel="help"
+  href="/WICG/webpackage/blob/main/explainers/subresource-loading.md"
+/>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/test-helpers.js"></script>
+
+<body>
+  <script>
+    window.TEST_WEB_BUNDLE_ELEMENT_TYPE = "script";
+    setup(() => {
+      assert_true(HTMLScriptElement.supports("webbundle"));
+    });
+
+    const wbn_url = "../resources/wbn/subresource.wbn";
+    const resource1 = "../resources/wbn/root.js";
+    const resource2 = "../resources/wbn/submodule.js";
+
+    let script1;
+    let script2;
+
+    function cleanUp() {
+      if (script1) {
+        script1.remove();
+      }
+      if (script2) {
+        script2.remove();
+      }
+    }
+
+    async function assertResource1CanBeFetched() {
+      const response = await fetch(resource1);
+      const text = await response.text();
+      assert_equals(text, "export * from './submodule.js';\n");
+    }
+
+    async function assertResource1CanNotBeFetched() {
+      const response = await fetch(resource1);
+      assert_equals(response.status, 404);
+    }
+
+    async function assertResource2CanBeFetched() {
+      const response = await fetch(resource2);
+      const text = await response.text();
+      assert_equals(text, "export const result = 'OK';\n");
+    }
+
+    function createScriptWebBundle1() {
+      return createWebBundleElement(wbn_url, /*resources=*/ [resource1]);
+    }
+
+    function createScriptWebBundle2() {
+      return createWebBundleElement(wbn_url, /*resources=*/ [resource2]);
+    }
+
+    async function appendScriptWebBundle1AndFetchResource1() {
+      clearWebBundleFetchCount();
+      script1 = createScriptWebBundle1();
+      document.body.append(script1);
+      await assertResource1CanBeFetched();
+      assert_equals(webBundleFetchCount(), 1);
+    }
+
+    function clearWebBundleFetchCount() {
+      performance.clearResourceTimings();
+    }
+
+    function webBundleFetchCount() {
+      return performance
+        .getEntriesByType("resource")
+        .filter((e) => e.name.endsWith("subresource.wbn")).length;
+    }
+
+    promise_test(async (t) => {
+      t.add_cleanup(cleanUp);
+      await appendScriptWebBundle1AndFetchResource1();
+      clearWebBundleFetchCount();
+
+      // Append script2 without removing script1.
+      // script2 should fetch the wbn again.
+      script2 = createScriptWebBundle2();
+      document.body.appendChild(script2);
+
+      await assertResource1CanBeFetched()
+      await assertResource2CanBeFetched();
+      assert_equals(webBundleFetchCount(), 1);
+    }, "A webbundle should be fetched again when new script element is appended.");
+
+    promise_test(async (t) => {
+      t.add_cleanup(cleanUp);
+      await appendScriptWebBundle1AndFetchResource1();
+      clearWebBundleFetchCount();
+
+      // Remove script1, then append script2
+      // script2 should reuse webbundle resources.
+      script1.remove();
+      script2 = createScriptWebBundle2();
+      document.body.append(script2);
+
+      await assertResource1CanNotBeFetched();
+      await assertResource2CanBeFetched();
+      assert_equals(webBundleFetchCount(), 0);
+    }, "'remove(), then append()' should reuse webbundle resources");
+
+    promise_test(async (t) => {
+      t.add_cleanup(cleanUp);
+      await appendScriptWebBundle1AndFetchResource1();
+      clearWebBundleFetchCount();
+
+      // Remove script1, then append the removed one.
+      script1.remove();
+      document.body.append(script1);
+
+      await assertResource1CanNotBeFetched();
+      assert_equals(webBundleFetchCount(), 0);
+    }, "'remove(), then append()' for the same element should reuse webbundle resources");
+
+    promise_test(async (t) => {
+      t.add_cleanup(cleanUp);
+      await appendScriptWebBundle1AndFetchResource1();
+      clearWebBundleFetchCount();
+
+      // Multiple 'remove(), then append()' for the same element.
+      script1.remove();
+      document.body.append(script1);
+
+      script1.remove();
+      document.body.append(script1);
+
+      await assertResource1CanNotBeFetched();
+      assert_equals(webBundleFetchCount(), 0);
+    }, "Multiple 'remove(), then append()' for the same element should reuse webbundle resources");
+
+
+    promise_test(async (t) => {
+      t.add_cleanup(cleanUp);
+      await appendScriptWebBundle1AndFetchResource1();
+      clearWebBundleFetchCount();
+
+      // Remove script1.
+      script1.remove();
+
+      // Then append script2 in a separet task.
+      await new Promise(resolve => t.step_timeout(resolve, 0));
+      script2 = createScriptWebBundle2();
+      document.body.append(script2);
+
+      await assertResource1CanNotBeFetched();
+      await assertResource2CanBeFetched();
+      assert_equals(webBundleFetchCount(), 1);
+    }, "'remove(), then append() in a separate task' should not reuse webbundle resources");
+
+
+    promise_test(async (t) => {
+      t.add_cleanup(cleanUp);
+      await appendScriptWebBundle1AndFetchResource1();
+      clearWebBundleFetchCount();
+
+      // Use replaceWith() to replace script1 with script2.
+      // script2 should reuse webbundle resources.
+      script2 = createScriptWebBundle2();
+      script1.replaceWith(script2);
+
+      await assertResource1CanNotBeFetched();
+      await assertResource2CanBeFetched();
+
+      assert_equals(webBundleFetchCount(), 0);
+    }, "replaceWith() should reuse webbundle resources.");
+
+    promise_test(async (t) => {
+      t.add_cleanup(cleanUp);
+      await appendScriptWebBundle1AndFetchResource1();
+      clearWebBundleFetchCount();
+
+      // Move script1 to another document. Then append script2.
+      // script2 should reuse webbundle resources.
+      const another_document = new Document();
+      another_document.append(script1);
+      script2 = createScriptWebBundle2();
+      document.body.append(script2);
+
+      await assertResource1CanNotBeFetched();
+      await assertResource2CanBeFetched();
+
+      assert_equals(webBundleFetchCount(), 0);
+
+      // TODO: Test the following cases:
+      // - The resources are not loaded from the webbundle in the new Document
+      // (Probably better to use a <iframe>.contentDocument)
+      // - Even if we move the script element back to the original Document,
+      // even immediately, the resources are not loaded from the webbundle in the
+      // original Document.
+    }, "append() should reuse webbundle resoruces even if the old script was moved to another document.");
+
+  </script>
+</body>
diff --git a/web-bundle/subresource-loading/script-supports-webbundle.https.tentative.html b/web-bundle/subresource-loading/script-supports-webbundle.https.tentative.html
new file mode 100644
index 00000000000000..b211a662158403
--- /dev/null
+++ b/web-bundle/subresource-loading/script-supports-webbundle.https.tentative.html
@@ -0,0 +1,16 @@
+<DOCTYPE html>
+<html>
+<title>HTMLScriptElement.supports webbundle</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+test(() => {
+  assert_true(HTMLScriptElement.supports('webbundle'));
+}, 'HTMLScriptElement.supports returns true for \'webbundle\'');
+
+test(() => {
+  assert_false(HTMLScriptElement.supports(' webbundle'));
+  assert_false(HTMLScriptElement.supports('webbundle '));
+  assert_false(HTMLScriptElement.supports('WEBBUNDLE'));
+}, 'HTMLScriptElement.supports returns false for unsupported types');
+</script>
