More tests, more memory leak fixes, etc

flecs_ecs/src/core/utility/functions.rs

@@ -381,9 +381,6 @@ pub(crate) fn set_helper<T: ComponentId>(
             //
             // For that reason, we could use `ecs_emplace_id`, but then on_replace hooks would not
             // be registerable on any of our components.
-            //
-            // The set pipeline for default constructed components works like so if deferred:
-            // Default constructed -> Dropped -> Moved into from value 
             // This code could be significantly more simple if ecs_emplace_id worked with `on_replace`
             // hooks, but that will require modifications to flecs.c, so this will have to suffice for now.
             let res = sys::ecs_cpp_set(
@@ -395,18 +392,18 @@ pub(crate) fn set_helper<T: ComponentId>(
             );
 
             let comp = res.ptr as *mut T;
+            // The set pipeline for default constructed components works like so:
+            // Default constructed -> Dropped -> Moved into from value 
+            // Default construction happens in sys::ecs_cpp_set.
+            core::ptr::drop_in_place(comp);
             core::ptr::write(comp, value);
 
             if res.call_modified {
                 sys::ecs_modified_id(world, entity, id);
             }
         } else {
-            // If T does not impl default, we need to construct the data ourselves.
-            // The reason we don't do this with T::IMPLS_DEFAULT is because ecs_emplace_id
-            // does not work with on_replace hooks and will assert.
-            //
-            // This creates a requirement that any component that implements an on_replace hook
-            // must have a Default constructor.
+            // If T does not impl Default, we need to construct the data ourselves.
+            // so that uninitialized data is not dropped.
             let mut changed: bool = false;
 
             let comp = sys::ecs_emplace_id(

flecs_ecs/src/core/world/world.rs

@@ -3,7 +3,7 @@ use core::ptr::NonNull;
 use flecs_ecs_sys as sys;
 
 use crate::core::{
-    FlecsArray, FlecsIdMap, QueryBuilderImpl, SystemAPI, WorldCtx, ecs_os_api, flecs
+    FlecsArray, FlecsIdMap, QueryBuilderImpl, SystemAPI, WorldCtx, ecs_os_api, flecs, has_default_hook
 };
 
 /// The `World` is the container for all ECS data. It stores the entities and

flecs_ecs/tests/flecs/component_lifecycle_test.rs

@@ -154,6 +154,25 @@ fn component_lifecycle_drop_on_world_delete() {
         world.progress();
     }
 
+    let init_boxes = INITIALIZED_BOXES.lock().unwrap();
+    assert!(
+        init_boxes.is_empty(),
+        "Leaked memory, objects not properly deleted: {:?}",
+        init_boxes
+    );
+}
+
+#[test]
+fn component_lifecycle_set_multiple_times() {
+    let world = World::new();
+
+    let ent = world
+        .entity_named("object 1")
+        .set(BoxedNumber::new("Object 1"));
+    ent.set(BoxedNumber::new("Object 2"));
+    ent.set(BoxedNumber::new("Object 3"));
+    ent.destruct();
+
     let init_boxes = INITIALIZED_BOXES.lock().unwrap();
     assert!(
         init_boxes.is_empty(),