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Reflect Struct QOL #22708

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7298c5c
Branched from dynamic_struct_removal
Diddykonga Jan 25, 2026
9705844
Suggestion: change field comparison and update tests
Diddykonga Jan 25, 2026
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22 changes: 12 additions & 10 deletions crates/bevy_ecs/src/reflect/bundle.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -166,7 +166,7 @@ impl<B: Bundle + Reflect + TypePath + BundleFromComponents> FromType<B> for Refl
match reflected_bundle.reflect_ref() {
ReflectRef::Struct(bundle) => bundle
.iter_fields()
.for_each(|field| apply_field(&mut entity, field, registry)),
.for_each(|(_, field)| apply_field(&mut entity, field, registry)),
ReflectRef::Tuple(bundle) => bundle
.iter_fields()
.for_each(|field| apply_field(&mut entity, field, registry)),
Expand Down Expand Up @@ -195,15 +195,17 @@ impl<B: Bundle + Reflect + TypePath + BundleFromComponents> FromType<B> for Refl
);
} else {
match reflected_bundle.reflect_ref() {
ReflectRef::Struct(bundle) => bundle.iter_fields().for_each(|field| {
apply_or_insert_field_mapped(
entity,
field,
registry,
mapper,
relationship_hook_mode,
);
}),
ReflectRef::Struct(bundle) => {
bundle.iter_fields().for_each(|(_, field)| {
apply_or_insert_field_mapped(
entity,
field,
registry,
mapper,
relationship_hook_mode,
);
});
}
ReflectRef::Tuple(bundle) => bundle.iter_fields().for_each(|field| {
apply_or_insert_field_mapped(
entity,
Expand Down
20 changes: 18 additions & 2 deletions crates/bevy_reflect/derive/src/impls/structs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,23 @@ pub(crate) fn impl_struct(reflect_struct: &ReflectStruct) -> proc_macro2::TokenS
}
}

fn name_of(&self, field: &dyn #bevy_reflect_path::PartialReflect) -> #FQOption<&str> {
#(if #bevy_reflect_path::PartialReflect::reflect_partial_eq(#fields_ref, field).unwrap_or(false) { return #fqoption::Some(#field_names) })*
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@alice-i-cecile alice-i-cecile Jan 26, 2026

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Nit: you can probably clean this up by using ? out of the reflect_partial_eq.

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@MrGVSV MrGVSV Jan 26, 2026

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As mentioned in this comment, I'm still not fully sold on this behavior.

To summarize my thoughts, I believe this behavior (i.e. where a field from one struct returns None on a field of another struct of the same type) may be too unintuitive.

I'm on board with index_by_name (though I think it should be renamed to index_of) and name_at, but index_of (in its current form) and name_of seem too situational and easy to mess up.

I'm willing to change my mind if people feel strongly that this is useful/necessary, though.

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@MrGVSV MrGVSV Jan 26, 2026

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One idea for getting around the limitations I mention here, is to instead make name_of and friends return a Result with a potential error of like NameOfError::NonUniqueFieldType. And then return that error if the struct contains two of the same type field.

But I don't love that idea as it still is super limiting (just not as much).

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@MrGVSV MrGVSV Jan 26, 2026

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Another option that I think would work better is to provide a low-level API for working with struct field pointers and addresses directly. Then you could do something like:

let api = TheApi::from(&my_struct);
let field: NamedField = api.field_at_addr(&my_struct.field).unwrap();
let name = field.name();

In fact, renaming Struct::name_of to Struct::name_at_addr or something would probably be an okay compromise. But I still also don't know if this sort of low level API belongs in Struct (of course, the benefit is that we don't have to go through get_represented_type_info).

#FQOption::None
}

fn index_of(&self, field: &dyn #bevy_reflect_path::PartialReflect) -> #FQOption<usize> {
#(if #bevy_reflect_path::PartialReflect::reflect_partial_eq(#fields_ref, field).unwrap_or(false) { return #fqoption::Some(#field_indices) })*
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@alice-i-cecile alice-i-cecile Jan 26, 2026

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Same comment as above.

#FQOption::None
}

fn index_of_name(&self, name: &str) -> #FQOption<usize> {
match name {
#(#field_names => #fqoption::Some(#field_indices),)*
_ => #FQOption::None,
}
}

fn field_len(&self) -> usize {
#field_count
}
Expand Down Expand Up @@ -144,8 +161,7 @@ pub(crate) fn impl_struct(reflect_struct: &ReflectStruct) -> proc_macro2::TokenS
) -> #FQResult<(), #bevy_reflect_path::ApplyError> {
if let #bevy_reflect_path::ReflectRef::Struct(struct_value)
= #bevy_reflect_path::PartialReflect::reflect_ref(value) {
for (i, value) in ::core::iter::Iterator::enumerate(#bevy_reflect_path::structs::Struct::iter_fields(struct_value)) {
let name = #bevy_reflect_path::structs::Struct::name_at(struct_value, i).unwrap();
for (name, value) in #bevy_reflect_path::structs::Struct::iter_fields(struct_value) {
if let #FQOption::Some(v) = #bevy_reflect_path::structs::Struct::field_mut(self, name) {
#bevy_reflect_path::PartialReflect::try_apply(v, value)?;
}
Expand Down
2 changes: 1 addition & 1 deletion crates/bevy_reflect/src/enums/dynamic_enum.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -246,7 +246,7 @@ impl Enum for DynamicEnum {

fn index_of(&self, name: &str) -> Option<usize> {
if let DynamicVariant::Struct(data) = &self.variant {
data.index_of(name)
data.index_of_name(name)
} else {
None
}
Expand Down
2 changes: 1 addition & 1 deletion crates/bevy_reflect/src/lib.rs
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Expand Up @@ -1117,7 +1117,7 @@ mod tests {

let values: Vec<u32> = foo
.iter_fields()
.map(|value| *value.try_downcast_ref::<u32>().unwrap())
.map(|(_, value)| *value.try_downcast_ref::<u32>().unwrap())
.collect();
assert_eq!(values, vec![1]);
}
Expand Down
2 changes: 1 addition & 1 deletion crates/bevy_reflect/src/serde/ser/structs.rs
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Expand Up @@ -48,7 +48,7 @@ impl<P: ReflectSerializerProcessor> Serialize for StructSerializer<'_, P> {
self.struct_value.field_len() - ignored_len,
)?;

for (index, value) in self.struct_value.iter_fields().enumerate() {
for (index, (_, value)) in self.struct_value.iter_fields().enumerate() {
if serialization_data.is_some_and(|data| data.is_field_skipped(index)) {
continue;
}
Expand Down
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