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# Objective Currently, the term "value" in the context of reflection is a bit overloaded. For one, it can be used synonymously with "data" or "variable". An example sentence would be "this function takes a reflected value". However, it is also used to refer to reflected types which are `ReflectKind::Value`. These types are usually either primitives, opaque types, or types that don't fall into any other `ReflectKind` (or perhaps could, but don't due to some limitation/difficulty). An example sentence would be "this function takes a reflected value type". This makes it difficult to write good documentation or other learning material without causing some amount of confusion to readers. Ideally, we'd be able to move away from the `ReflectKind::Value` usage and come up with a better term. ## Solution This PR replaces the terminology of "value" with "opaque" across `bevy_reflect`. This includes in documentation, type names, variant names, and macros. The term "opaque" was chosen because that's essentially how the type is treated within the reflection API. In other words, its internal structure is hidden. All we can do is work with the type itself. ### Primitives While primitives are not technically opaque types, I think it's still clearer to refer to them as "opaque" rather than keep the confusing "value" terminology. We could consider adding another concept for primitives (e.g. `ReflectKind::Primitive`), but I'm not sure that provides a lot of benefit right now. In most circumstances, they'll be treated just like an opaque type. They would also likely use the same macro (or two copies of the same macro but with different names). ## Testing You can test locally by running: ``` cargo test --package bevy_reflect --all-features ``` --- ## Migration Guide The reflection concept of "value type" has been replaced with a clearer "opaque type". The following renames have been made to account for this: - `ReflectKind::Value` → `ReflectKind::Opaque` - `ReflectRef::Value` → `ReflectRef::Opaque` - `ReflectMut::Value` → `ReflectMut::Opaque` - `ReflectOwned::Value` → `ReflectOwned::Opaque` - `TypeInfo::Value` → `TypeInfo::Opaque` - `ValueInfo` → `OpaqueInfo` - `impl_reflect_value!` → `impl_reflect_opaque!` - `impl_from_reflect_value!` → `impl_from_reflect_opaque!` Additionally, declaring your own opaque types no longer uses `#[reflect_value]`. This attribute has been replaced by `#[reflect(opaque)]`: ```rust // BEFORE #[derive(Reflect)] #[reflect_value(Default)] struct MyOpaqueType(u32); // AFTER #[derive(Reflect)] #[reflect(opaque)] #[reflect(Default)] struct MyOpaqueType(u32); ``` Note that the order in which `#[reflect(opaque)]` appears does not matter. |
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