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Author SHA1 Message Date
Gino Valente
aeeb20ec4c
bevy_reflect: FromReflect Ergonomics Implementation (#6056) 
# Objective

**This implementation is based on
https://github.com/bevyengine/rfcs/pull/59.**

---

Resolves #4597

Full details and motivation can be found in the RFC, but here's a brief
summary.

`FromReflect` is a very powerful and important trait within the
reflection API. It allows Dynamic types (e.g., `DynamicList`, etc.) to
be formed into Real ones (e.g., `Vec<i32>`, etc.).

This mainly comes into play concerning deserialization, where the
reflection deserializers both return a `Box<dyn Reflect>` that almost
always contain one of these Dynamic representations of a Real type. To
convert this to our Real type, we need to use `FromReflect`.

It also sneaks up in other ways. For example, it's a required bound for
`T` in `Vec<T>` so that `Vec<T>` as a whole can be made `FromReflect`.
It's also required by all fields of an enum as it's used as part of the
`Reflect::apply` implementation.

So in other words, much like `GetTypeRegistration` and `Typed`, it is
very much a core reflection trait.

The problem is that it is not currently treated like a core trait and is
not automatically derived alongside `Reflect`. This makes using it a bit
cumbersome and easy to forget.

## Solution

Automatically derive `FromReflect` when deriving `Reflect`.

Users can then choose to opt-out if needed using the
`#[reflect(from_reflect = false)]` attribute.

```rust
#[derive(Reflect)]
struct Foo;

#[derive(Reflect)]
#[reflect(from_reflect = false)]
struct Bar;

fn test<T: FromReflect>(value: T) {}

test(Foo); // <-- OK
test(Bar); // <-- Panic! Bar does not implement trait `FromReflect`
```

#### `ReflectFromReflect`

This PR also automatically adds the `ReflectFromReflect` (introduced in
#6245) registration to the derived `GetTypeRegistration` impl— if the
type hasn't opted out of `FromReflect` of course.

<details>
<summary><h4>Improved Deserialization</h4></summary>

> **Warning**
> This section includes changes that have since been descoped from this
PR. They will likely be implemented again in a followup PR. I am mainly
leaving these details in for archival purposes, as well as for reference
when implementing this logic again.

And since we can do all the above, we might as well improve
deserialization. We can now choose to deserialize into a Dynamic type or
automatically convert it using `FromReflect` under the hood.

`[Un]TypedReflectDeserializer::new` will now perform the conversion and
return the `Box`'d Real type.

`[Un]TypedReflectDeserializer::new_dynamic` will work like what we have
now and simply return the `Box`'d Dynamic type.

```rust
// Returns the Real type
let reflect_deserializer = UntypedReflectDeserializer::new(&registry);
let mut deserializer = ron:🇩🇪:Deserializer::from_str(input)?;

let output: SomeStruct = reflect_deserializer.deserialize(&mut deserializer)?.take()?;

// Returns the Dynamic type
let reflect_deserializer = UntypedReflectDeserializer::new_dynamic(&registry);
let mut deserializer = ron:🇩🇪:Deserializer::from_str(input)?;

let output: DynamicStruct = reflect_deserializer.deserialize(&mut deserializer)?.take()?;
```

</details>

---

## Changelog

* `FromReflect` is now automatically derived within the `Reflect` derive
macro
* This includes auto-registering `ReflectFromReflect` in the derived
`GetTypeRegistration` impl
* ~~Renamed `TypedReflectDeserializer::new` and
`UntypedReflectDeserializer::new` to
`TypedReflectDeserializer::new_dynamic` and
`UntypedReflectDeserializer::new_dynamic`, respectively~~ **Descoped**
* ~~Changed `TypedReflectDeserializer::new` and
`UntypedReflectDeserializer::new` to automatically convert the
deserialized output using `FromReflect`~~ **Descoped**

## Migration Guide

* `FromReflect` is now automatically derived within the `Reflect` derive
macro. Items with both derives will need to remove the `FromReflect`
one.

  ```rust
  // OLD
  #[derive(Reflect, FromReflect)]
  struct Foo;
  
  // NEW
  #[derive(Reflect)]
  struct Foo;
  ```

If using a manual implementation of `FromReflect` and the `Reflect`
derive, users will need to opt-out of the automatic implementation.

  ```rust
  // OLD
  #[derive(Reflect)]
  struct Foo;
  
  impl FromReflect for Foo {/* ... */}
  
  // NEW
  #[derive(Reflect)]
  #[reflect(from_reflect = false)]
  struct Foo;
  
  impl FromReflect for Foo {/* ... */}
  ```

<details>
<summary><h4>Removed Migrations</h4></summary>

> **Warning**
> This section includes changes that have since been descoped from this
PR. They will likely be implemented again in a followup PR. I am mainly
leaving these details in for archival purposes, as well as for reference
when implementing this logic again.

* The reflect deserializers now perform a `FromReflect` conversion
internally. The expected output of `TypedReflectDeserializer::new` and
`UntypedReflectDeserializer::new` is no longer a Dynamic (e.g.,
`DynamicList`), but its Real counterpart (e.g., `Vec<i32>`).

  ```rust
let reflect_deserializer =
UntypedReflectDeserializer::new_dynamic(&registry);
  let mut deserializer = ron:🇩🇪:Deserializer::from_str(input)?;
  
  // OLD
let output: DynamicStruct = reflect_deserializer.deserialize(&mut
deserializer)?.take()?;
  
  // NEW
let output: SomeStruct = reflect_deserializer.deserialize(&mut
deserializer)?.take()?;
  ```

Alternatively, if this behavior isn't desired, use the
`TypedReflectDeserializer::new_dynamic` and
`UntypedReflectDeserializer::new_dynamic` methods instead:

  ```rust
  // OLD
  let reflect_deserializer = UntypedReflectDeserializer::new(&registry);
  
  // NEW
let reflect_deserializer =
UntypedReflectDeserializer::new_dynamic(&registry);
  ```

</details>

---------

Co-authored-by: Carter Anderson <mcanders1@gmail.com>
 2023-06-29 01:31:34 +00:00
radiish
1efc762924
reflect: stable type path v2 (#7184) 
# Objective

- Introduce a stable alternative to
[`std::any::type_name`](https://doc.rust-lang.org/std/any/fn.type_name.html).
- Rewrite of #5805 with heavy inspiration in design.
- On the path to #5830.
- Part of solving #3327.


## Solution

- Add a `TypePath` trait for static stable type path/name information.
- Add a `TypePath` derive macro.
- Add a `impl_type_path` macro for implementing internal and foreign
types in `bevy_reflect`.

---

## Changelog

- Added `TypePath` trait.
- Added `DynamicTypePath` trait and `get_type_path` method to `Reflect`.
- Added a `TypePath` derive macro.
- Added a `bevy_reflect::impl_type_path` for implementing `TypePath` on
internal and foreign types in `bevy_reflect`.
- Changed `bevy_reflect::utility::(Non)GenericTypeInfoCell` to
`(Non)GenericTypedCell<T>` which allows us to be generic over both
`TypeInfo` and `TypePath`.
- `TypePath` is now a supertrait of `Asset`, `Material` and
`Material2d`.
- `impl_reflect_struct` needs a `#[type_path = "..."]` attribute to be
specified.
- `impl_reflect_value` needs to either specify path starting with a
double colon (`::core::option::Option`) or an `in my_crate::foo`
declaration.
- Added `bevy_reflect_derive::ReflectTypePath`.
- Most uses of `Ident` in `bevy_reflect_derive` changed to use
`ReflectTypePath`.

## Migration Guide

- Implementors of `Asset`, `Material` and `Material2d` now also need to
derive `TypePath`.
- Manual implementors of `Reflect` will need to implement the new
`get_type_path` method.

## Open Questions
- [x] ~This PR currently does not migrate any usages of
`std::any::type_name` to use `bevy_reflect::TypePath` to ease the review
process. Should it?~ Migration will be left to a follow-up PR.
- [ ] This PR adds a lot of `#[derive(TypePath)]` and `T: TypePath` to
satisfy new bounds, mostly when deriving `TypeUuid`. Should we make
`TypePath` a supertrait of `TypeUuid`? [Should we remove `TypeUuid` in
favour of
`TypePath`?](2afbd85532 (r961067892))
 2023-06-05 20:31:20 +00:00
Charles Bournhonesque
cbb4c26cad Enable deriving Reflect on structs with generic types (#7364) 
# Objective

I recently had an issue, where I have a struct:
```
struct Property {
   inner: T
}
```
that I use as a wrapper for internal purposes.
I don't want to update my struct definition to 
```
struct Property<T: Reflect>{
   inner: T
}
```
because I still want to be able to build `Property<T>` for types `T` that are not `Reflect`. (and also because I don't want to update my whole code base with `<T: Reflect>` bounds)

I still wanted to have reflection on it (for `bevy_inspector_egui`), but adding `derive(Reflect)` fails with the error:
`T cannot be sent between threads safely. T needs to implement Sync.`

I believe that `bevy_reflect` should adopt the model of other derives in the case of generics, which is to add the `Reflect` implementation only if the generics also implement `Reflect`. (That is the behaviour of other macros such as `derive(Clone)` or `derive(Debug)`.

It's also the current behavior of `derive(FromReflect)`.

Basically doing something like:
```
impl<T> Reflect for Foo<T>
where T: Reflect
```


## Solution

- I updated the derive macros for `Structs` and `TupleStructs` to add extra `where` bounds.
   -  Every type that is reflected will need a `T: Reflect` bound
   -  Ignored types will need a `T: 'static + Send + Sync` bound. Here's the reason. For cases like this:
```
#[derive(Reflect)]
struct Foo<T, U>{
   a: T
   #[reflect(ignore)]
   b: U
}
```
I had to add the bound `'static + Send + Sync` to ignored generics like `U`.
The reason is that we want `Foo<T, U>` to be `Reflect: 'static + Send + Sync`, so `Foo<T, U>` must be able to implement those auto-traits. `Foo<T, U>` will only implement those auto-traits if every generic type implements them, including ignored types.
This means that the previously compile-fail case now compiles:
```
#[derive(Reflect)]
struct Foo<'a> {
    #[reflect(ignore)]
    value: &'a str,
}
```
But `Foo<'a>` will only be useable in the cases where `'a: 'static` and panic if we don't have `'a: 'static`, which is what we want (nice bonus from this PR ;) )



---

## Changelog

> This section is optional. If this was a trivial fix, or has no externally-visible impact, you can delete this section.

### Added
Possibility to add `derive(Reflect)` to structs and enums that contain generic types, like so:
```
#[derive(Reflect)]
struct Foo<T>{
   a: T
}
```
Reflection will only be available if the generic type T also implements `Reflect`.
(previously, this would just return a compiler error)
 2023-01-28 00:12:06 +00:00
Elbert Ronnie
f9c52f98b9 Make proc macros hygienic in bevy_reflect_derive (#6752) 
# Objective

- Fixes #3004 

## Solution

- Replaced all the types with their fully quallified names
- Replaced all trait methods and inherent methods on dyn traits with their fully qualified names
- Made a new file `fq_std.rs` that contains structs corresponding to commonly used Structs and Traits from `std`. These structs are replaced by their respective fully qualified names when used inside `quote!`
 2022-12-05 23:39:44 +00:00
Jakob Hellermann
e71c4d2802 fix nightly clippy warnings (#6395) 
# Objective

- fix new clippy lints before they get stable and break CI

## Solution

- run `clippy --fix` to auto-fix machine-applicable lints
- silence `clippy::should_implement_trait` for `fn HandleId::default<T: Asset>`

## Changes
- always prefer `format!("{inline}")` over `format!("{}", not_inline)`
- prefer `Box::default` (or `Box::<T>::default` if necessary) over `Box::new(T::default())`
 2022-10-28 21:03:01 +00:00
Maksymilian Mozolewski
ac1aebed5e Add reflect(skip_serializing) which retains reflection but disables automatic serialization (#5250) 
# Objective

- To address problems outlined in https://github.com/bevyengine/bevy/issues/5245

## Solution

- Introduce `reflect(skip_serializing)` on top of `reflect(ignore)` which disables automatic serialisation to scenes, but does not disable reflection of the field.

---

## Changelog
- Adds: 
  - `bevy_reflect::serde::type_data` module
  - `SerializationData` structure for describing which fields are to be/not to be ignored, automatically registers as type_data for struct-based types
  - the `skip_serialization` flag for `#[reflect(...)]`
 - Removes:
   - ability to ignore Enum variants in serialization, since that didn't work anyway   
 

## Migration Guide
- Change `#[reflect(ignore)]` to `#[reflect(skip_serializing)]` where disabling reflection is not the intended effect.
- Remove ignore/skip attributes from enum variants as these won't do anything anymore
 2022-09-19 16:12:10 +00:00
Jakob Hellermann
7dcfaaef67 bevy_reflect: ReflectFromPtr to create &dyn Reflect from a *const () (#4475) 
# Objective

https://github.com/bevyengine/bevy/pull/4447 adds functions that can fetch resources/components as `*const ()` ptr by providing the `ComponentId`. This alone is not enough for them to be usable safely with reflection, because there is no general way to go from the raw pointer to a `&dyn Reflect` which is the pointer + a pointer to the VTable of the `Reflect` impl.

By adding a `ReflectFromPtr` type that is included in the type type registration when deriving `Reflect`, safe functions can be implemented in scripting languages that don't assume a type layout and can access the component data via reflection:

```rust
#[derive(Reflect)]
struct StringResource {
    value: String
}
```

```lua
local res_id = world:resource_id_by_name("example::StringResource")
local res = world:resource(res_id)

print(res.value)
```

## Solution

1. add a `ReflectFromPtr` type with a `FromType<T: Reflect>` implementation and the following methods:
- `     pub unsafe fn as_reflect_ptr<'a>(&self, val: Ptr<'a>) -> &'a dyn Reflect`
- `     pub unsafe fn as_reflect_ptr_mut<'a>(&self, val: PtrMut<'a>) -> &'a mud dyn Reflect`

Safety requirements of the methods are that you need to check that the `ReflectFromPtr` was constructed for the correct type.

2. add that type to the `TypeRegistration` in the `GetTypeRegistration` impl generated by `#[derive(Reflect)]`.
This is different to other reflected traits because it doesn't need `#[reflect(ReflectReflectFromPtr)]` which IMO should be there by default.

Co-authored-by: Jakob Hellermann <hellermann@sipgate.de>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
 2022-07-19 23:00:34 +00:00
MrGVSV
3d8d922566 bevy_reflect_derive: Tidying up the code (#4712) 
# Objective

The `bevy_reflect_derive` crate is not the cleanest or easiest to follow/maintain. The `lib.rs` file is especially difficult with over 1000 lines of code written in a confusing order. This is just a result of growth within the crate and it would be nice to clean it up for future work.

## Solution

Split `bevy_reflect_derive` into many more submodules. The submodules include:

* `container_attributes` - Code relating to container attributes
* `derive_data` - Code relating to reflection-based derive metadata
* `field_attributes` - Code relating to field attributes
* `impls` - Code containing actual reflection implementations
* `reflect_value` - Code relating to reflection-based value metadata
* `registration` - Code relating to type registration
* `utility` - General-purpose utility functions

This leaves the `lib.rs` file to contain only the public macros, making it much easier to digest (and fewer than 200 lines).

By breaking up the code into smaller modules, we make it easier for future contributors to find the code they're looking for or identify which module best fits their own additions.

### Metadata Structs

This cleanup also adds two big metadata structs: `ReflectFieldAttr` and `ReflectDeriveData`. The former is used to store all attributes for a struct field (if any). The latter is used to store all metadata for struct-based derive inputs.

Both significantly reduce code duplication and make editing these macros much simpler. The tradeoff is that we may collect more metadata than needed. However, this is usually a small thing (such as checking for attributes when they're not really needed or creating a `ReflectFieldAttr` for every field regardless of whether they actually have an attribute).

We could try to remove these tradeoffs and squeeze some more performance out, but doing so might come at the cost of developer experience. Personally, I think it's much nicer to create a `ReflectFieldAttr` for every field since it means I don't have to do two `Option` checks. Others may disagree, though, and so we can discuss changing this either in this PR or in a future one.

### Out of Scope

_Some_ documentation has been added or improved, but ultimately good docs are probably best saved for a dedicated PR.

## 🔍 Focus Points (for reviewers)

I know it's a lot to sift through, so here is a list of **key points for reviewers**:

- The following files contain code that was mostly just relocated:
  - `reflect_value.rs`
  - `registration.rs`
- `container_attributes.rs` was also mostly moved but features some general cleanup (reducing nesting, removing hardcoded strings, etc.) and lots of doc comments
- Most impl logic was moved from `lib.rs` to `impls.rs`, but they have been significantly modified to use the new `ReflectDeriveData` metadata struct in order to reduce duplication.
- `derive_data.rs` and `field_attributes.rs` contain almost entirely new code and should probably be given the most attention.
- Likewise, `from_reflect.rs` saw major changes using `ReflectDeriveData` so it should also be given focus.
- There was no change to the `lib.rs` exports so the end-user API should be the same.

## Prior Work

This task was initially tackled by @NathanSWard in #2377 (which was closed in favor of this PR), so hats off to them for beating me to the punch by nearly a year!

---

## Changelog

* **[INTERNAL]** Split `bevy_reflect_derive` into smaller submodules
* **[INTERNAL]** Add `ReflectFieldAttr`
* **[INTERNAL]** Add `ReflectDeriveData`
* Add `BevyManifest::get_path_direct()` method (`bevy_macro_utils`)


Co-authored-by: MrGVSV <49806985+MrGVSV@users.noreply.github.com>
 2022-05-12 19:43:23 +00:00