LibWeb/WebAssembly: Change behavior of explicit `undefined` in tables

Userland/Libraries/LibWeb/WebAssembly/Table.cpp

@@ -29,19 +29,14 @@ static Wasm::ValueType table_kind_to_value_type(Bindings::TableKind kind)
     VERIFY_NOT_REACHED();
 }
 
-static JS::ThrowCompletionOr<Wasm::Value> value_to_reference(JS::VM& vm, JS::Value value, Wasm::ValueType const& reference_type)
-{
-    if (value.is_undefined() && reference_type.kind() != Wasm::ValueType::Kind::ExternReference)
-        return Wasm::Value(reference_type);
-    return Detail::to_webassembly_value(vm, value, reference_type);
-}
-
 WebIDL::ExceptionOr<JS::NonnullGCPtr<Table>> Table::construct_impl(JS::Realm& realm, TableDescriptor& descriptor, JS::Value value)
 {
     auto& vm = realm.vm();
 
     auto reference_type = table_kind_to_value_type(descriptor.element);
-    auto reference_value = TRY(value_to_reference(vm, value, reference_type));
+    auto reference_value = vm.argument_count() == 1
+        ? Detail::default_webassembly_value(vm, reference_type)
+        : TRY(Detail::to_webassembly_value(vm, value, reference_type));
 
     Wasm::Limits limits { descriptor.initial, move(descriptor.maximum) };
     Wasm::TableType table_type { reference_type, move(limits) };
@@ -83,7 +78,9 @@ WebIDL::ExceptionOr<u32> Table::grow(u32 delta, JS::Value value)
 
     auto initial_size = table->elements().size();
 
-    auto reference_value = TRY(value_to_reference(vm, value, table->type().element_type()));
+    auto reference_value = vm.argument_count() == 1
+        ? Detail::default_webassembly_value(vm, table->type().element_type())
+        : TRY(Detail::to_webassembly_value(vm, value, table->type().element_type()));
     auto const& reference = reference_value.to<Wasm::Reference>();
 
     if (!table->grow(delta, reference))
@@ -124,7 +121,9 @@ WebIDL::ExceptionOr<void> Table::set(u32 index, JS::Value value)
     if (table->elements().size() <= index)
         return vm.throw_completion<JS::RangeError>("Table element index out of range"sv);
 
-    auto reference_value = TRY(value_to_reference(vm, value, table->type().element_type()));
+    auto reference_value = vm.argument_count() == 1
+        ? Detail::default_webassembly_value(vm, table->type().element_type())
+        : TRY(Detail::to_webassembly_value(vm, value, table->type().element_type()));
     auto const& reference = reference_value.to<Wasm::Reference>();
 
     table->elements()[index] = reference;

Userland/Libraries/LibWeb/WebAssembly/WebAssembly.cpp

@@ -455,6 +455,22 @@ JS::ThrowCompletionOr<Wasm::Value> to_webassembly_value(JS::VM& vm, JS::Value va
     VERIFY_NOT_REACHED();
 }
 
+Wasm::Value default_webassembly_value(JS::VM& vm, Wasm::ValueType type)
+{
+    switch (type.kind()) {
+    case Wasm::ValueType::I32:
+    case Wasm::ValueType::I64:
+    case Wasm::ValueType::F32:
+    case Wasm::ValueType::F64:
+    case Wasm::ValueType::V128:
+    case Wasm::ValueType::FunctionReference:
+        return Wasm::Value(type);
+    case Wasm::ValueType::ExternReference:
+        return MUST(to_webassembly_value(vm, JS::js_undefined(), type));
+    }
+    VERIFY_NOT_REACHED();
+}
+
 // https://webassembly.github.io/spec/js-api/#tojsvalue
 JS::Value to_js_value(JS::VM& vm, Wasm::Value& wasm_value, Wasm::ValueType type)
 {

Userland/Libraries/LibWeb/WebAssembly/WebAssembly.h

@@ -66,6 +66,7 @@ JS::ThrowCompletionOr<NonnullOwnPtr<Wasm::ModuleInstance>> instantiate_module(JS
 JS::ThrowCompletionOr<NonnullRefPtr<CompiledWebAssemblyModule>> parse_module(JS::VM&, JS::Object* buffer);
 JS::NativeFunction* create_native_function(JS::VM&, Wasm::FunctionAddress address, ByteString const& name, Instance* instance = nullptr);
 JS::ThrowCompletionOr<Wasm::Value> to_webassembly_value(JS::VM&, JS::Value value, Wasm::ValueType const& type);
+Wasm::Value default_webassembly_value(JS::VM&, Wasm::ValueType type);
 JS::Value to_js_value(JS::VM&, Wasm::Value& wasm_value, Wasm::ValueType type);
 
 extern HashMap<JS::GCPtr<JS::Object>, WebAssemblyCache> s_caches;