bevy/crates/bevy_reflect/src/impls/smallvec.rs
Gino Valente aa241672e1
bevy_reflect: Nested TypeInfo getters (#13321)
# Objective

Right now, `TypeInfo` can be accessed directly from a type using either
`Typed::type_info` or `Reflect::get_represented_type_info`.

However, once that `TypeInfo` is accessed, any nested types must be
accessed via the `TypeRegistry`.

```rust
#[derive(Reflect)]
struct Foo {
  bar: usize
}

let registry = TypeRegistry::default();

let TypeInfo::Struct(type_info) = Foo::type_info() else {
  panic!("expected struct info");
};

let field = type_info.field("bar").unwrap();

let field_info = registry.get_type_info(field.type_id()).unwrap();
assert!(field_info.is::<usize>());;
```

## Solution

Enable nested types within a `TypeInfo` to be retrieved directly.

```rust
#[derive(Reflect)]
struct Foo {
  bar: usize
}

let TypeInfo::Struct(type_info) = Foo::type_info() else {
  panic!("expected struct info");
};

let field = type_info.field("bar").unwrap();

let field_info = field.type_info().unwrap();
assert!(field_info.is::<usize>());;
```

The particular implementation was chosen for two reasons.

Firstly, we can't just store `TypeInfo` inside another `TypeInfo`
directly. This is because some types are recursive and would result in a
deadlock when trying to create the `TypeInfo` (i.e. it has to create the
`TypeInfo` before it can use it, but it also needs the `TypeInfo` before
it can create it). Therefore, we must instead store the function so it
can be retrieved lazily.

I had considered also using a `OnceLock` or something to lazily cache
the info, but I figured we can look into optimizations later. The API
should remain the same with or without the `OnceLock`.

Secondly, a new wrapper trait had to be introduced: `MaybeTyped`. Like
`RegisterForReflection`, this trait is `#[doc(hidden)]` and only exists
so that we can properly handle dynamic type fields without requiring
them to implement `Typed`. We don't want dynamic types to implement
`Typed` due to the fact that it would make the return type
`Option<&'static TypeInfo>` for all types even though only the dynamic
types ever need to return `None` (see #6971 for details).

Users should never have to interact with this trait as it has a blanket
impl for all `Typed` types. And `Typed` is automatically implemented
when deriving `Reflect` (as it is required).

The one downside is we do need to return `Option<&'static TypeInfo>`
from all these new methods so that we can handle the dynamic cases. If
we didn't have to, we'd be able to get rid of the `Option` entirely. But
I think that's an okay tradeoff for this one part of the API, and keeps
the other APIs intact.

## Testing

This PR contains tests to verify everything works as expected. You can
test locally by running:

```
cargo test --package bevy_reflect
```

---

## Changelog

### Public Changes

- Added `ArrayInfo::item_info` method
- Added `NamedField::type_info` method
- Added `UnnamedField::type_info` method
- Added `ListInfo::item_info` method
- Added `MapInfo::key_info` method
- Added `MapInfo::value_info` method
- All active fields now have a `Typed` bound (remember that this is
automatically satisfied for all types that derive `Reflect`)

### Internal Changes

- Added `MaybeTyped` trait

## Migration Guide

All active fields for reflected types (including lists, maps, tuples,
etc.), must implement `Typed`. For the majority of users this won't have
any visible impact.

However, users implementing `Reflect` manually may need to update their
types to implement `Typed` if they weren't already.

Additionally, custom dynamic types will need to implement the new hidden
`MaybeTyped` trait.
2024-07-15 00:40:07 +00:00

192 lines
5.3 KiB
Rust

use bevy_reflect_derive::impl_type_path;
use smallvec::{Array as SmallArray, SmallVec};
use std::any::Any;
use crate::utility::GenericTypeInfoCell;
use crate::{
self as bevy_reflect, ApplyError, FromReflect, FromType, GetTypeRegistration, List, ListInfo,
ListIter, MaybeTyped, Reflect, ReflectFromPtr, ReflectKind, ReflectMut, ReflectOwned,
ReflectRef, TypeInfo, TypePath, TypeRegistration, Typed,
};
impl<T: SmallArray + TypePath + Send + Sync> List for SmallVec<T>
where
T::Item: FromReflect + MaybeTyped + TypePath,
{
fn get(&self, index: usize) -> Option<&dyn Reflect> {
if index < SmallVec::len(self) {
Some(&self[index] as &dyn Reflect)
} else {
None
}
}
fn get_mut(&mut self, index: usize) -> Option<&mut dyn Reflect> {
if index < SmallVec::len(self) {
Some(&mut self[index] as &mut dyn Reflect)
} else {
None
}
}
fn insert(&mut self, index: usize, value: Box<dyn Reflect>) {
let value = value.take::<T::Item>().unwrap_or_else(|value| {
<T as SmallArray>::Item::from_reflect(&*value).unwrap_or_else(|| {
panic!(
"Attempted to insert invalid value of type {}.",
value.reflect_type_path()
)
})
});
SmallVec::insert(self, index, value);
}
fn remove(&mut self, index: usize) -> Box<dyn Reflect> {
Box::new(self.remove(index))
}
fn push(&mut self, value: Box<dyn Reflect>) {
let value = value.take::<T::Item>().unwrap_or_else(|value| {
<T as SmallArray>::Item::from_reflect(&*value).unwrap_or_else(|| {
panic!(
"Attempted to push invalid value of type {}.",
value.reflect_type_path()
)
})
});
SmallVec::push(self, value);
}
fn pop(&mut self) -> Option<Box<dyn Reflect>> {
self.pop().map(|value| Box::new(value) as Box<dyn Reflect>)
}
fn len(&self) -> usize {
<SmallVec<T>>::len(self)
}
fn iter(&self) -> ListIter {
ListIter::new(self)
}
fn drain(self: Box<Self>) -> Vec<Box<dyn Reflect>> {
self.into_iter()
.map(|value| Box::new(value) as Box<dyn Reflect>)
.collect()
}
}
impl<T: SmallArray + TypePath + Send + Sync> Reflect for SmallVec<T>
where
T::Item: FromReflect + MaybeTyped + TypePath,
{
fn get_represented_type_info(&self) -> Option<&'static TypeInfo> {
Some(<Self as Typed>::type_info())
}
fn into_any(self: Box<Self>) -> Box<dyn Any> {
self
}
fn as_any(&self) -> &dyn Any {
self
}
fn as_any_mut(&mut self) -> &mut dyn Any {
self
}
fn into_reflect(self: Box<Self>) -> Box<dyn Reflect> {
self
}
fn as_reflect(&self) -> &dyn Reflect {
self
}
fn as_reflect_mut(&mut self) -> &mut dyn Reflect {
self
}
fn apply(&mut self, value: &dyn Reflect) {
crate::list_apply(self, value);
}
fn try_apply(&mut self, value: &dyn Reflect) -> Result<(), ApplyError> {
crate::list_try_apply(self, value)
}
fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>> {
*self = value.take()?;
Ok(())
}
fn reflect_kind(&self) -> ReflectKind {
ReflectKind::List
}
fn reflect_ref(&self) -> ReflectRef {
ReflectRef::List(self)
}
fn reflect_mut(&mut self) -> ReflectMut {
ReflectMut::List(self)
}
fn reflect_owned(self: Box<Self>) -> ReflectOwned {
ReflectOwned::List(self)
}
fn clone_value(&self) -> Box<dyn Reflect> {
Box::new(self.clone_dynamic())
}
fn reflect_partial_eq(&self, value: &dyn Reflect) -> Option<bool> {
crate::list_partial_eq(self, value)
}
}
impl<T: SmallArray + TypePath + Send + Sync + 'static> Typed for SmallVec<T>
where
T::Item: FromReflect + MaybeTyped + TypePath,
{
fn type_info() -> &'static TypeInfo {
static CELL: GenericTypeInfoCell = GenericTypeInfoCell::new();
CELL.get_or_insert::<Self, _>(|| TypeInfo::List(ListInfo::new::<Self, T::Item>()))
}
}
impl_type_path!(::smallvec::SmallVec<T: SmallArray>);
impl<T: SmallArray + TypePath + Send + Sync> FromReflect for SmallVec<T>
where
T::Item: FromReflect + MaybeTyped + TypePath,
{
fn from_reflect(reflect: &dyn Reflect) -> Option<Self> {
if let ReflectRef::List(ref_list) = reflect.reflect_ref() {
let mut new_list = Self::with_capacity(ref_list.len());
for field in ref_list.iter() {
new_list.push(<T as SmallArray>::Item::from_reflect(field)?);
}
Some(new_list)
} else {
None
}
}
}
impl<T: SmallArray + TypePath + Send + Sync> GetTypeRegistration for SmallVec<T>
where
T::Item: FromReflect + MaybeTyped + TypePath,
{
fn get_type_registration() -> TypeRegistration {
let mut registration = TypeRegistration::of::<SmallVec<T>>();
registration.insert::<ReflectFromPtr>(FromType::<SmallVec<T>>::from_type());
registration
}
}
#[cfg(feature = "functions")]
crate::func::macros::impl_function_traits!(SmallVec<T>; <T: SmallArray + TypePath + Send + Sync> where T::Item: FromReflect + MaybeTyped + TypePath);