fix: Let tag components call get_component, add missing export

BUILD.bazel

@@ -132,6 +132,7 @@ ecsact_build_recipe(
     exports = [
         # core
         "ecsact_execute_systems",
+        "ecsact_create_registry",
         "ecsact_destroy_registry",
         "ecsact_clear_registry",
         "ecsact_create_entity",
@@ -163,6 +164,8 @@ ecsact_build_recipe(
     ],
 )
 
+exports_files(["build_recipe.yml"])
+
 ecsact_build_recipe_bundle(
     name = "ecsact_rt_entt",
     recipes = [":ecsact_rt_entt_recipe"],

ecsact/entt/wrapper/core.hh

@@ -32,6 +32,10 @@ inline auto get_component(
 	[[maybe_unused]] ecsact_component_id component_id,
 	...
 ) -> const void* {
+	if constexpr(std::is_empty_v<C>) {
+		static C emptyVal;
+		return &emptyVal;
+	}
 	auto& reg = ecsact::entt::get_registry(registry_id);
 	auto  entity = ecsact::entt::entity_id{entity_id};
 	assert(C::id == component_id);

rt_entt_codegen/rt_entt_codegen.cc

@@ -195,19 +195,13 @@ void ecsact_codegen_plugin(
 			return;
 		}
 
-		auto non_tag_component_ids =
-			details.all_components |
-			std::views::filter([&](ecsact_component_id comp_id) -> bool {
-				return !ecsact::meta::get_field_ids(comp_id).empty();
-			});
-
 		ctx.write(
 			"result.reserve(",
-			std::ranges::distance(non_tag_component_ids),
+			std::ranges::distance(details.all_components),
 			");\n"
 		);
 
-		for(auto comp_id : non_tag_component_ids) {
+		for(auto comp_id : details.all_components) {
 			auto cpp_comp_name = cpp_identifier(decl_full_name(comp_id));
 			ctx.write(
 				"result.insert({::",