22250: Adds EvalOnEntity to Amalgam API, MINOR (#324)

`EvalOnEntity(handle, "(arbitrary_code)")` runs that code in the context
of some entity.

src/Amalgam/Amalgam.h

@@ -60,6 +60,8 @@ extern "C"
 	AMALGAM_EXPORT wchar_t *ExecuteEntityJsonPtrWide(char *handle, char *label, char *json);
 	AMALGAM_EXPORT char *ExecuteEntityJsonPtr(char *handle, char *label, char *json);
 
+	AMALGAM_EXPORT char *EvalOnEntity(char *handle, char *amlg);
+
 	AMALGAM_EXPORT wchar_t *GetVersionStringWide();
 	AMALGAM_EXPORT char *GetVersionString();
 

src/Amalgam/AmalgamAPI.cpp

@@ -202,6 +202,14 @@ extern "C"
 		entint.ExecuteEntity(h, l);
 	}
 
+	char *EvalOnEntity(char *handle, char *amlg)
+	{
+		std::string h(handle);
+		std::string a(amlg);
+		std::string ret = entint.EvalOnEntity(h, a);
+		return StringToCharPtr(ret);
+	}
+
 	void DestroyEntity(char *handle)
 	{
 		std::string h(handle);

src/Amalgam/AmalgamTrace.cpp

@@ -31,6 +31,7 @@ int32_t RunAmalgamTrace(std::istream *in_stream, std::ostream *out_stream, std::
 	std::string input;
 	std::string handle;
 	std::string label;
+	std::string amlg;
 	std::string clone_handle;
 	std::string command;
 	std::string path;
@@ -188,6 +189,12 @@ int32_t RunAmalgamTrace(std::istream *in_stream, std::ostream *out_stream, std::
 			json_payload = input;  // json data
 			response = entint.ExecuteEntityJSON(handle, label, json_payload);
 		}
+		else if(command == "EVAL_ON_ENTITY")
+		{
+			handle = StringManipulation::RemoveFirstToken(input);
+			amlg = StringManipulation::RemoveFirstToken(input);
+			response = entint.EvalOnEntity(handle, amlg);
+		}
 		else if(command == "SET_RANDOM_SEED")
 		{
 			handle = StringManipulation::RemoveFirstToken(input);

src/Amalgam/entity/EntityExternalInterface.cpp

@@ -260,6 +260,39 @@ std::string EntityExternalInterface::ExecuteEntityJSON(std::string &handle, std:
 	return (converted ? result : string_intern_pool.GetStringFromID(string_intern_pool.NOT_A_STRING_ID));
 }
 
+std::string EntityExternalInterface::EvalOnEntity(const std::string &handle, const std::string &amlg)
+{
+	auto bundle = FindEntityBundle(handle);
+	if(bundle == nullptr)
+		return "";
+
+	EvaluableNodeManager &enm = bundle->entity->evaluableNodeManager;
+#ifdef MULTITHREAD_SUPPORT
+	//lock memory before allocating call stack
+	Concurrency::ReadLock enm_lock(enm.memoryModificationMutex);
+#endif
+
+	auto [code, warnings, offset] = Parser::Parse(amlg, &enm);
+	if(code == nullptr)
+		return "";
+
+	auto call_stack = Interpreter::ConvertArgsToCallStack(EvaluableNodeReference::Null(), enm);
+
+	EvaluableNodeReference returned_value = bundle->entity->ExecuteCodeAsEntity(code, call_stack, nullptr,
+		&bundle->writeListeners, bundle->printListener, nullptr
+#ifdef MULTITHREAD_SUPPORT
+		, &enm_lock
+#endif
+	);
+
+	enm.FreeNode(call_stack);
+	enm.FreeNodeTreeIfPossible(code);
+
+	auto [result, converted] = EvaluableNodeJSONTranslation::EvaluableNodeToJson(returned_value);
+	enm.FreeNodeTreeIfPossible(returned_value);
+	return (converted ? result : string_intern_pool.GetStringFromID(string_intern_pool.NOT_A_STRING_ID));
+}
+
 bool EntityExternalInterface::EntityListenerBundle::SetEntityValueAtLabel(std::string &label_name, EvaluableNodeReference new_value)
 {
 	StringInternPool::StringID label_sid = string_intern_pool.GetIDFromString(label_name);

src/Amalgam/entity/EntityExternalInterface.h

@@ -58,6 +58,7 @@ class EntityExternalInterface
 	bool SetJSONToLabel(std::string &handle, std::string &label, std::string_view json);
 	std::string GetJSONFromLabel(std::string &handle, std::string &label);
 	std::string ExecuteEntityJSON(std::string &handle, std::string &label, std::string_view json);
+	std::string EvalOnEntity(const std::string &handle, const std::string &amlg);
 
 protected:
 
@@ -171,7 +172,7 @@ class EntityExternalInterface
 	};
 
 	//looks up the bundle and returns it, will return nullptr if not found
-	inline EntityListenerBundleReadReference FindEntityBundle(std::string &handle)
+	inline EntityListenerBundleReadReference FindEntityBundle(const std::string &handle)
 	{
 	#ifdef MULTITHREAD_INTERFACE
 		Concurrency::ReadLock read_lock(mutex);

test/lib_smoke_test/main.cpp

@@ -22,13 +22,21 @@ int main(int argc, char* argv[])
 	char write_log[] = "";
 	char print_log[] = "";
 	auto status = LoadEntity(handle, file, file_type, false, json_file_params, write_log, print_log);
-	if(status.loaded)
+	if(!status.loaded)
+		return 1;
+
+	int retval = 0;
+	char label[] = "test";
+	ExecuteEntity(handle, label);
+
+	std::string amlg("(size (contained_entities))");
+	std::string result = EvalOnEntity(handle, amlg.data());
+	if(result != std::string("24"))
 	{
-		char label[] = "test";
-		ExecuteEntity(handle, label);
-		DestroyEntity(handle);
-		return 0;
+		std::cerr << "EvalOnEntity produced " << result << " but expected 24";
+		retval = 1;
 	}
 
-	return 1;
+	DestroyEntity(handle);
+	return retval;
 }