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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Kenton Varda <kenton@cloudflare.com>
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Date: Wed, 4 Dec 2024 22:36:05 -0600
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Subject: Add ValueSerializer::SetTreatProxiesAsHostObjects().
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Previously, ValueSerializer would always refuse to serialize Proxy objects. This commit gives the embedder the option to handle them as host objects.
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Similar to the previous patch adding `SetTreatFunctionsAsHostObjects()`, this is intended for use in an RPC system, where an arbitrary object can be "serialized" by replacing it with a stub which, when invoked, performs an RPC back to the originating isolate in order to access the original object there.
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Signed-off-by: James M Snell <jsnell@cloudflare.com>
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diff --git a/include/v8-value-serializer.h b/include/v8-value-serializer.h
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index 141f138e08de849e3e02b3b2b346e643b9e40c70..bdcb2831c55e21c6d511f56dfc79a5076871f05a 100644
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--- a/include/v8-value-serializer.h
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+++ b/include/v8-value-serializer.h
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@@ -204,6 +204,15 @@ class V8_EXPORT ValueSerializer {
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    */
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   void SetTreatFunctionsAsHostObjects(bool mode);
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+  /**
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+   * Indicate whether to treat Proxies as host objects,
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+   * i.e. pass them to Delegate::WriteHostObject. This should not be
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+   * called when no Delegate was passed.
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+   *
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+   * The default is not to treat Proxies as host objects.
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+   */
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+  void SetTreatProxiesAsHostObjects(bool mode);
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+
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   /**
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    * Write raw data in various common formats to the buffer.
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    * Note that integer types are written in base-128 varint format, not with a
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diff --git a/src/api/api.cc b/src/api/api.cc
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index 178b429ad06ea349bb43dff578b27ae46ae14da7..8754d87f1db985d4021faf9ce275783ae1229dc8 100644
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--- a/src/api/api.cc
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+++ b/src/api/api.cc
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@@ -3592,6 +3592,10 @@ void ValueSerializer::SetTreatFunctionsAsHostObjects(bool mode) {
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   private_->serializer.SetTreatFunctionsAsHostObjects(mode);
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 }
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+void ValueSerializer::SetTreatProxiesAsHostObjects(bool mode) {
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+  private_->serializer.SetTreatProxiesAsHostObjects(mode);
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+}
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+
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 Maybe<bool> ValueSerializer::WriteValue(Local<Context> context,
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                                         Local<Value> value) {
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   auto i_isolate = i::Isolate::Current();
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diff --git a/src/objects/value-serializer.cc b/src/objects/value-serializer.cc
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index 8c0bf0824b200489919f46b18d240c8c5c15a8ec..13d1a1340de579b8242bc3193c8c9002ecfd0468 100644
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--- a/src/objects/value-serializer.cc
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+++ b/src/objects/value-serializer.cc
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@@ -339,6 +339,10 @@ void ValueSerializer::SetTreatFunctionsAsHostObjects(bool mode) {
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   treat_functions_as_host_objects_ = mode;
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 }
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+void ValueSerializer::SetTreatProxiesAsHostObjects(bool mode) {
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+  treat_proxies_as_host_objects_ = mode;
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+}
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+
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 void ValueSerializer::WriteTag(SerializationTag tag) {
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   uint8_t raw_tag = static_cast<uint8_t>(tag);
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   WriteRawBytes(&raw_tag, sizeof(raw_tag));
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@@ -610,7 +614,12 @@ Maybe<bool> ValueSerializer::WriteJSReceiver(
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   InstanceType instance_type = receiver->map()->instance_type();
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   if (IsCallable(*receiver)) {
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     if (treat_functions_as_host_objects_) {
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-      return WriteHostObject(Cast<JSObject>(receiver));
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+      return WriteHostObject(receiver);
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+    }
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+    return ThrowDataCloneError(MessageTemplate::kDataCloneError, receiver);
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+  } else if (instance_type == JS_PROXY_TYPE) {
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+    if (treat_proxies_as_host_objects_) {
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+      return WriteHostObject(receiver);
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     }
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     return ThrowDataCloneError(MessageTemplate::kDataCloneError, receiver);
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   } else if (IsSpecialReceiverInstanceType(instance_type) &&
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@@ -1288,7 +1297,7 @@ Maybe<bool> ValueSerializer::WriteSharedObject(
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   return ThrowIfOutOfMemory();
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 }
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-Maybe<bool> ValueSerializer::WriteHostObject(DirectHandle<JSObject> object) {
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+Maybe<bool> ValueSerializer::WriteHostObject(DirectHandle<JSReceiver> object) {
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   WriteTag(SerializationTag::kHostObject);
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   if (!delegate_) {
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     isolate_->Throw(*isolate_->factory()->NewError(
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diff --git a/src/objects/value-serializer.h b/src/objects/value-serializer.h
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index ddc5f27a80f93bae209f3fe8731d4df4baa58ead..496aab365007a45806264c8d3b981bd7a494f903 100644
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--- a/src/objects/value-serializer.h
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+++ b/src/objects/value-serializer.h
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@@ -111,6 +111,15 @@ class ValueSerializer {
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    */
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   void SetTreatFunctionsAsHostObjects(bool mode);
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+  /*
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+   * Indicate whether to treat Proxies as host objects,
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+   * i.e. pass them to Delegate::WriteHostObject. This should not be
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+   * called when no Delegate was passed.
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+   *
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+   * The default is not to treat Proxies as host objects.
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+   */
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+  void SetTreatProxiesAsHostObjects(bool mode);
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+
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  private:
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   // Managing allocations of the internal buffer.
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   Maybe<bool> ExpandBuffer(size_t required_capacity);
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@@ -161,8 +170,7 @@ class ValueSerializer {
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 #endif  // V8_ENABLE_WEBASSEMBLY
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   Maybe<bool> WriteSharedObject(DirectHandle<HeapObject> object)
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       V8_WARN_UNUSED_RESULT;
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-  Maybe<bool> WriteHostObject(DirectHandle<JSObject> object)
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-      V8_WARN_UNUSED_RESULT;
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+  Maybe<bool> WriteHostObject(DirectHandle<JSReceiver> object) V8_WARN_UNUSED_RESULT;
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   /*
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    * Reads the specified keys from the object and writes key-value pairs to the
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@@ -195,6 +203,7 @@ class ValueSerializer {
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   bool has_custom_host_objects_ = false;
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   bool treat_array_buffer_views_as_host_objects_ = false;
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   bool treat_functions_as_host_objects_ = false;
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+  bool treat_proxies_as_host_objects_ = false;
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   bool out_of_memory_ = false;
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   Zone zone_;
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   uint32_t version_;