Fix #22865 non_snake_case on bundle derive

[SOF3]

Objective

Fixes #22865

Solution

Add #[allow(non_snake_case)] to avoid validating the field variable format.

Testing

• Did you test these changes? If so, how?
• Are there any parts that need more testing?
• How can other people (reviewers) test your changes? Is there anything specific they need to know?
• If relevant, what platforms did you test these changes on, and are there any important ones you can't test?

[Copilot]

Pull request overview

Fixes the new non_snake_case warning emitted by code generated via deconstruct_moving_ptr! when field-derived locals end up with names like field__marker (regression noted in #22865, bevy_ecs 0.18).

Changes:

• Adds #[allow(non_snake_case)] to let bindings generated in the tuple and MaybeUninit::<tuple> arms of deconstruct_moving_ptr!.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

This only adds #[allow(non_snake_case)] to the tuple (let tuple { ... }) and MaybeUninit::<tuple> arms. The derive(Bundle) expansion that triggered #22865 uses the struct-pattern arms (let StructName { field: field_local, ... } = ptr;), which still expand to let field__marker = ...; without an allow, so the original warning is likely unchanged. Consider applying the same #[allow(non_snake_case)] to the struct and MaybeUninit::<Struct> arms as well (the ones using get_pattern!).

[alice-i-cecile]

Please add a comment explaining why this allow is needed :)

[alice-i-cecile]

Ditto on the comment here.

[SOF3]

CI is failing due to a GitHub network error, could you trigger a rerun?

[chescock]

This doesn't seem like the right place to fix this. If a user wants to provide a non-snake-case identifier, can't they write #[allow(non_snake_case)] outside the macro invocation?

Looking at the linked issue, I see this is happening with #[derive(Bundle)]. ... Ah, okay, that generates local variables by doing format_ident!("field_{}", field_member), so it gets field__marker with two underscores when the field is _marker.

bevy/crates/bevy_ecs/macros/src/lib.rs

Line 115 in d1c3557

let field_local = format_ident!("field_{}", field_member);

I think it would be better to add #[allow(non_snake_case)] to the output of #[derive(Bundle)], since that's what's generating the non-snake-case identifier. That lets us preserve the warning for hand-written deconstruct_moving_ptr calls that do want that lint.

That would mean adding it to the DynamicBundle::get_components method, since that's where the deconstruct_moving_ptr call is:

bevy/crates/bevy_ecs/macros/src/lib.rs

Lines 154 to 164 in d1c3557

	#[allow(unused_variables)]
	#[inline]
	unsafe fn get_components(
	ptr: #ecs_path::ptr::MovingPtr<'_, Self>,
	func: &mut impl FnMut(#ecs_path::component::StorageType, #ecs_path::ptr::OwningPtr<'_>)
	) {
	use #ecs_path::__macro_exports::DebugCheckedUnwrap;
	#ecs_path::ptr::deconstruct_moving_ptr!({
	let #struct_name { #(#active_field_members: #active_field_locals,)* #(#inactive_field_members: _,)* } = ptr;
	});