[web snapshot] Support top-level non-objects

Currently, the serializer and deserializer assume that all top-level
declarations to be serialized will be objects.

This CL removes this assumption.

Bug: v8:11525, v8:11706
Change-Id: I5acf5e7a3b73aba5ffc5b1d5eb9cb51b3804a4af
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2945178Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Vicky Kontoura <vkont@google.com>
Cr-Commit-Position: refs/heads/master@{#75020}

src/web-snapshot/web-snapshot.cc

@@ -412,17 +412,22 @@ void WebSnapshotSerializer::SerializePendingObject(Handle<JSObject> object) {
 
 // Format (serialized export):
 // - String id (export name)
-// - Object id (exported object)
+// - Serialized value (export value)
 void WebSnapshotSerializer::SerializeExport(Handle<JSObject> object,
                                             Handle<String> export_name) {
-  // TODO(v8:11525): Support exporting functions.
   ++export_count_;
   uint32_t string_id = 0;
   SerializeString(export_name, string_id);
-  uint32_t object_id = 0;
-  SerializeObject(object, object_id);
   export_serializer_.WriteUint32(string_id);
-  export_serializer_.WriteUint32(object_id);
+  if (object->IsJSPrimitiveWrapper()) {
+    Handle<JSPrimitiveWrapper> wrapper =
+        Handle<JSPrimitiveWrapper>::cast(object);
+    Handle<Object> export_value =
+        handle(JSPrimitiveWrapper::cast(*wrapper).value(), isolate_);
+    WriteValue(export_value, export_serializer_);
+  } else {
+    WriteValue(object, export_serializer_);
+  }
 }
 
 // Format (serialized value):
@@ -901,12 +906,9 @@ void WebSnapshotDeserializer::DeserializeExports() {
   }
   for (uint32_t i = 0; i < count; ++i) {
     Handle<String> export_name = ReadString(true);
-    uint32_t object_id = 0;
-    if (!deserializer_->ReadUint32(&object_id) || object_id >= object_count_) {
-      Throw("Web snapshot: Malformed export");
-      return;
-    }
-    Handle<Object> exported_object = handle(objects_->get(object_id), isolate_);
+    Handle<Object> export_value;
+    Representation representation;
+    ReadValue(export_value, representation);
 
     // Check for the correctness of the snapshot (thus far) before producing
     // something observable. TODO(v8:11525): Strictly speaking, we should
@@ -917,7 +919,7 @@ void WebSnapshotDeserializer::DeserializeExports() {
     }
 
     auto result = Object::SetProperty(isolate_, isolate_->global_object(),
-                                      export_name, exported_object);
+                                      export_name, export_value);
     if (result.is_null()) {
       Throw("Web snapshot: Setting global property failed");
       return;

test/mjsunit/web-snapshot/web-snapshot.js

@@ -68,6 +68,16 @@ function takeAndUseWebSnapshot(createObjects, exports) {
   assertEquals(Number.NEGATIVE_INFINITY, foo.f);
 })();
 
+(function TestTopLevelNumbers() {
+  function createObjects() {
+    globalThis.a = 6;
+    globalThis.b = -7;
+  }
+  const { a, b } = takeAndUseWebSnapshot(createObjects, ['a', 'b']);
+  assertEquals(6, a);
+  assertEquals(-7, b);
+})();
+
 (function TestOddballs() {
   function createObjects() {
     globalThis.foo = {
@@ -84,6 +94,16 @@ function takeAndUseWebSnapshot(createObjects, exports) {
   assertEquals(undefined, foo.d);
 })();
 
+(function TestTopLevelOddballs() {
+  function createObjects() {
+    globalThis.a = true;
+    globalThis.b = false;
+  }
+  const { a, b } = takeAndUseWebSnapshot(createObjects, ['a', 'b']);
+  assertTrue(a);
+  assertFalse(b);
+})();
+
 (function TestFunction() {
   function createObjects() {
     globalThis.foo = {
@@ -128,6 +148,18 @@ function takeAndUseWebSnapshot(createObjects, exports) {
   assertEquals('snapshot', foo.key());
 })();
 
+(function TestTopLevelFunctionWithContext() {
+  function createObjects() {
+    globalThis.foo = (function () {
+      let result = 'bar';
+      function inner() { return result; }
+      return inner;
+    })();
+  }
+  const { foo } = takeAndUseWebSnapshot(createObjects, ['foo']);
+  assertEquals('bar', foo());
+})();
+
 (function TestRegExp() {
   function createObjects() {
     globalThis.foo = {
@@ -151,3 +183,13 @@ function takeAndUseWebSnapshot(createObjects, exports) {
   assertTrue(foo.re.test('abc'));
   assertFalse(foo.re.test('ac'));
 })();
+
+(function TestTopLevelRegExp() {
+  function createObjects() {
+    globalThis.re = /ab+c/gi;
+  }
+  const { re } = takeAndUseWebSnapshot(createObjects, ['re']);
+  assertEquals('/ab+c/gi', re.toString());
+  assertTrue(re.test('aBc'));
+  assertFalse(re.test('ac'));
+})();