ref counting the association internal compnent

ecsact/entt/detail/internal_markers.hh

@@ -10,6 +10,7 @@ template<typename C, std::size_t FieldOffset>
 struct association {
 	using component = C;
 	static constexpr auto field_offset = FieldOffset;
+	std::int_fast16_t     ref_count = 0;
 };
 
 template<typename Assoc>

ecsact/entt/detail/registry_info.hh

@@ -62,8 +62,17 @@ struct registry_info {
 
 		auto entity_field = field.template get<ecsact_entity_id>(&component);
 		auto entity_field_entt = entities_map.at(entity_field);
-		mp_with_index<64>(field.offset, [&](auto I) {
-			registry.emplace<association<C, I>>(entity_field_entt);
+		// TODO(zaucy): Increasing the mp_with_index number causes really long
+		//              compile times. Iterating over the available associations
+		//              would perform better here.
+		assert(field.offset < 32);
+		mp_with_index<32>(field.offset, [&](auto I) {
+			if(registry.all_of<association<C, I>>(entity_field_entt)) {
+				auto& assoc_comp = registry.get<association<C, I>>(entity_field_entt);
+				assoc_comp.ref_count += 1;
+			} else {
+				registry.emplace<association<C, I>>(entity_field_entt, 1);
+			}
 		});
 	}
 
@@ -77,8 +86,16 @@ struct registry_info {
 
 		auto entity_field = field.template get<ecsact_entity_id>(&component);
 		auto entity_field_entt = entities_map.at(entity_field);
-		mp_with_index<64>(field.offset, [&](auto I) {
-			registry.erase<association<C, I>>(entity_field_entt);
+		assert(field.offset < 32);
+		// TODO(zaucy): Increasing the mp_with_index number causes really long
+		//              compile times. Iterating over the available associations
+		//              would perform better here.
+		mp_with_index<32>(field.offset, [&](auto I) {
+			auto& assoc_comp = registry.get<association<C, I>>(entity_field_entt);
+			assoc_comp.ref_count -= 1;
+			if(assoc_comp.ref_count == 0) {
+				registry.erase<association<C, I>>(entity_field_entt);
+			}
 		});
 	}
 

ecsact/entt/detail/system_execution_context.hh

@@ -188,10 +188,12 @@ struct system_execution_context : system_execution_context_base {
 			}
 		}
 
-		info.registry.template emplace<pending_remove<C>>(entity);
+		// TODO(zaucy): Look into if emplace_or_replace is necessary instead of
+		//              just replace.
+		info.registry.template emplace_or_replace<pending_remove<C>>(entity);
 
 		if constexpr(!C::transient) {
-			info.registry.template emplace<component_removed<C>>(entity);
+			info.registry.template emplace_or_replace<component_removed<C>>(entity);
 		}
 	}
 

runtime/test/runtime_test.cc

@@ -87,6 +87,17 @@ void runtime_test::AddAssocTest::impl(context& ctx) {
 	target_ctx.add(AddAssocTestComponent{.num = 10});
 }
 
+static std::atomic_bool RemoveAssocTest_ran = false;
+
+void runtime_test::RemoveAssocTest::impl(context& ctx) {
+	RemoveAssocTest_ran = true;
+	auto other_entity = ctx.get<OtherEntityComponent>();
+
+	// Get Target other context from OtherEntityComponent
+	auto target_ctx = ctx._ctx.other(other_entity.target);
+	target_ctx.remove<RemoveAssocTestComponent>();
+}
+
 TEST(Core, CreateRegistry) {
 	auto reg_id = ecsact_create_registry("CreateRegistry");
 	EXPECT_NE(reg_id, ecsact_invalid_registry_id);
@@ -489,6 +500,69 @@ TEST(Core, AddAssocOk) {
 	EXPECT_EQ(exec_err, ECSACT_EXEC_SYS_OK);
 }
 
+TEST(Core, RemoveAssocOk) {
+	ecsact_set_system_execution_impl(
+		ecsact_id_cast<ecsact_system_like_id>(runtime_test::AssocTestAction::id),
+		&runtime_test__AssocTestAction
+	);
+	ecsact_set_system_execution_impl(
+		ecsact_id_cast<ecsact_system_like_id>(runtime_test::RemoveAssocTest::id),
+		&runtime_test__RemoveAssocTest
+	);
+
+	auto reg = ecsact::core::registry("RemoveAssocOk");
+	auto test_entity2 = reg.create_entity();
+	reg.add_component<runtime_test::RemoveAssocTestTag>(test_entity2);
+	reg.add_component(
+		test_entity2,
+		runtime_test::RemoveAssocTestComponent{
+			.num = 42,
+		}
+	);
+
+	auto test_entity1 = reg.create_entity();
+	reg.add_component(
+		test_entity1,
+		runtime_test::OtherEntityComponent{
+			.target = test_entity2,
+		}
+	);
+
+	auto test_entity3 = reg.create_entity();
+	reg.add_component(
+		test_entity3,
+		runtime_test::OtherEntityComponent{
+			.target = test_entity2,
+		}
+	);
+
+	RemoveAssocTest_ran = false;
+	auto exec_err = ecsact_execute_systems(reg.id(), 1, nullptr, nullptr);
+	EXPECT_TRUE(RemoveAssocTest_ran) << "RemoveAssocTest Impl Didn't Executed";
+	EXPECT_EQ(exec_err, ECSACT_EXEC_SYS_OK);
+
+	ASSERT_FALSE(
+		reg.has_component<runtime_test::RemoveAssocTestComponent>(test_entity2)
+	);
+
+	exec_err = ecsact_execute_systems(reg.id(), 1, nullptr, nullptr);
+	EXPECT_EQ(exec_err, ECSACT_EXEC_SYS_OK);
+
+	reg.add_component(
+		test_entity2,
+		runtime_test::RemoveAssocTestComponent{
+			.num = 42,
+		}
+	);
+
+	exec_err = ecsact_execute_systems(reg.id(), 1, nullptr, nullptr);
+	EXPECT_EQ(exec_err, ECSACT_EXEC_SYS_OK);
+
+	ASSERT_FALSE(
+		reg.has_component<runtime_test::RemoveAssocTestComponent>(test_entity2)
+	);
+}
+
 TEST(Core, AssociationEntityCorrectness) {
 	using runtime_test::AttackDamage;
 	using runtime_test::AttackDamageWeakened;

runtime/test/runtime_test.ecsact

@@ -75,6 +75,19 @@ system AddAssocTest {
 	}
 }
 
+component RemoveAssocTestComponent {
+	i32 num;
+}
+
+component RemoveAssocTestTag;
+
+system RemoveAssocTest {
+	readwrite OtherEntityComponent with target {
+		include RemoveAssocTestTag;
+		removes RemoveAssocTestComponent;
+	}
+}
+
 system AttackDamage {
 	readwrite Attacking with target {
 		readwrite Health;