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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: Sat, 2 Mar 2024 09:00:18 -0600
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Subject: Add ValueSerializer::SetTreatFunctionsAsHostObjects().
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Previously, ValueSerializer would always refuse to serialize functions. This commit gives the embedder the option to handle them as host objects.
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This is intended for use in an RPC system, where a function can be "serialized" by replacing it with a stub which, when invoked, performs an RPC back to the originating isolate in order to execute the original function 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 596be18adeb3a5a81794aaa44b1d347dec6c0c7d..141f138e08de849e3e02b3b2b346e643b9e40c70 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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@@ -195,6 +195,15 @@ class V8_EXPORT ValueSerializer {
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    */
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   void SetTreatArrayBufferViewsAsHostObjects(bool mode);
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+  /**
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+   * Indicate whether to treat Functions 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 Functions as host objects.
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+   */
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+  void SetTreatFunctionsAsHostObjects(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 2c226e1467d952fd80c5356f7993f8af00c5f35d..877765bf5f57a2953aa2d1e0869ae5db12e8b6b1 100644
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--- a/src/api/api.cc
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+++ b/src/api/api.cc
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@@ -3588,6 +3588,10 @@ void ValueSerializer::SetTreatArrayBufferViewsAsHostObjects(bool mode) {
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   private_->serializer.SetTreatArrayBufferViewsAsHostObjects(mode);
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 }
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+void ValueSerializer::SetTreatFunctionsAsHostObjects(bool mode) {
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+  private_->serializer.SetTreatFunctionsAsHostObjects(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 fc4dc2477d48c97145237e922d3bcba16140c47d..97b7f51664dda24ffb0c94e4033b2eff2ba4daee 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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@@ -335,6 +335,10 @@ void ValueSerializer::SetTreatArrayBufferViewsAsHostObjects(bool mode) {
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   treat_array_buffer_views_as_host_objects_ = mode;
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 }
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+void ValueSerializer::SetTreatFunctionsAsHostObjects(bool mode) {
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+  treat_functions_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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@@ -604,13 +608,17 @@ Maybe<bool> ValueSerializer::WriteJSReceiver(
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   // Eliminate callable and exotic objects, which should not be serialized.
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   InstanceType instance_type = receiver->map()->instance_type();
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-  if (IsCallable(*receiver) ||
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-      (IsSpecialReceiverInstanceType(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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+    }
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+    return ThrowDataCloneError(MessageTemplate::kDataCloneError, receiver);
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+  } else if (IsSpecialReceiverInstanceType(instance_type) &&
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        instance_type != JS_SPECIAL_API_OBJECT_TYPE
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 #if V8_ENABLE_WEBASSEMBLY
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        && instance_type != WASM_STRUCT_TYPE && instance_type != WASM_ARRAY_TYPE
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 #endif
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-       )) {
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+       ) {
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     return ThrowDataCloneError(MessageTemplate::kDataCloneError, receiver);
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   }
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diff --git a/src/objects/value-serializer.h b/src/objects/value-serializer.h
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index 06475f7b9c2a797066f5cfd32b232e5aa55f1f75..ddc5f27a80f93bae209f3fe8731d4df4baa58ead 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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@@ -102,6 +102,15 @@ class ValueSerializer {
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    */
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   void SetTreatArrayBufferViewsAsHostObjects(bool mode);
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+  /*
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+   * Indicate whether to treat Functions 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 Functions as host objects.
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+   */
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+  void SetTreatFunctionsAsHostObjects(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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@@ -185,6 +194,7 @@ class ValueSerializer {
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   size_t buffer_capacity_ = 0;
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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 out_of_memory_ = false;
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   Zone zone_;
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   uint32_t version_;