From ca6630a24a02884ff6dc9af29cdc0552f5fe5bfd Mon Sep 17 00:00:00 2001
From: urben1680 <55257931+urben1680@users.noreply.github.com>
Date: Sun, 16 Mar 2025 19:58:16 +0100
Subject: [PATCH] Introduce public `World::register_dynamic_bundle` method
 (#18198)

Registering dynamic bundles was not possible for the user yet.

It is alone not very useful though as there are no methods to clone,
move or remove components via a `BundleId`. This could be a follow-up
work if this PR is approved and such a third (besides `T: Bundle` and
`ComponentId`(s)) API for structural operation is desired. I certainly
would use a hypothetical `EntityClonerBuilder::allow_by_bundle_id`.

I personally still would like this register method because I have a
`Bundles`-like custom data structure and I would like to not reinvent
the wheel. Then instead of having boxed `ComponentId` slices in my
collection I could look up explicit and required components there.

For reference scroll up to the typed version right above the new one.
---
 crates/bevy_ecs/src/world/mod.rs | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/crates/bevy_ecs/src/world/mod.rs b/crates/bevy_ecs/src/world/mod.rs
index fc7e303b18..66a18faa3f 100644
--- a/crates/bevy_ecs/src/world/mod.rs
+++ b/crates/bevy_ecs/src/world/mod.rs
@@ -3117,6 +3117,25 @@ impl World {
         // SAFETY: We just initialized the bundle so its id should definitely be valid.
         unsafe { self.bundles.get(id).debug_checked_unwrap() }
     }
+
+    /// Registers the given [`ComponentId`]s as a dynamic bundle and returns both the required component ids and the bundle id.
+    ///
+    /// Note that the components need to be registered first, this function only creates a bundle combining them. Components
+    /// can be registered with [`World::register_component`]/[`_with_descriptor`](World::register_component_with_descriptor).
+    ///
+    /// **You should prefer to use the typed API [`World::register_bundle`] where possible and only use this in cases where
+    /// not all of the actual types are known at compile time.**
+    ///
+    /// # Panics
+    /// This function will panic if any of the provided component ids do not belong to a component known to this [`World`].
+    #[inline]
+    pub fn register_dynamic_bundle(&mut self, component_ids: &[ComponentId]) -> &BundleInfo {
+        let id =
+            self.bundles
+                .init_dynamic_info(&mut self.storages, &self.components, component_ids);
+        // SAFETY: We just initialized the bundle so its id should definitely be valid.
+        unsafe { self.bundles.get(id).debug_checked_unwrap() }
+    }
 }
 
 impl World {