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Make it so ParsedPath can be passed to GetPath (#9373)
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# Objective

- Unify the `ParsedPath` and `GetPath` APIs. They weirdly didn't play
well together.
- Make `ParsedPath` and `GetPath` API easier to use

## Solution

- Add the `ReflectPath` trait.
- `GetPath` methods now accept an `impl ReflectPath<'a>` instead of a
`&'a str`, this mean it also can accepts a `&ParsedPath`
- Make `GetPath: Reflect` and use default impl for `Reflect` types.
- Add `GetPath` and `ReflectPath` to the `bevy_reflect` prelude

---

## Changelog

- Add the `ReflectPath` trait.
- `GetPath` methods now accept an `impl ReflectPath<'a>` instead of a
`&'a str`, this mean it also can accept a `&ParsedPath`
- Make `GetPath: Reflect` and use default impl for `Reflect` types.
- Add `GetPath` and `ReflectPath` to the `bevy_reflect` prelude

## Migration Guide

`GetPath` now requires `Reflect`. This reduces a lot of boilerplate on
bevy's side. If you were implementing manually `GetPath` on your own
type, please get in touch!

`ParsedPath::element[_mut]` isn't an inherent method of `ParsedPath`,
you must now import `ReflectPath`. This is only relevant if you weren't
importing the bevy prelude.

```diff
-use bevy::reflect::ParsedPath;
+use bevy::reflect::{ParsedPath, ReflectPath};

 parsed_path.element(reflect_type).unwrap()
 parsed_path.element(reflect_type).unwrap()
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@nicopap
nicopap authored Aug 25, 2023
1 parent 7b0809b commit 7083f0d
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4 changes: 2 additions & 2 deletions crates/bevy_reflect/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -513,8 +513,8 @@ pub mod prelude {
pub use crate::std_traits::*;
#[doc(hidden)]
pub use crate::{
reflect_trait, FromReflect, GetField, GetTupleStructField, Reflect, ReflectDeserialize,
ReflectFromReflect, ReflectSerialize, Struct, TupleStruct,
reflect_trait, FromReflect, GetField, GetPath, GetTupleStructField, Reflect,
ReflectDeserialize, ReflectFromReflect, ReflectPath, ReflectSerialize, Struct, TupleStruct,
};
}

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184 changes: 76 additions & 108 deletions crates/bevy_reflect/src/path/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,8 @@ use thiserror::Error;

pub use parse::ParseError;

type PathResult<'a, T> = Result<T, ReflectPathError<'a>>;

/// An error specific to accessing a field/index on a `Reflect`.
#[derive(Debug, PartialEq, Eq, Error)]
#[error(transparent)]
Expand Down Expand Up @@ -37,6 +39,53 @@ pub enum ReflectPathError<'a> {
},
}

/// Something that can be interpreted as a reflection path in [`GetPath`].
pub trait ReflectPath<'a>: Sized {
/// Gets a reference to the specified element on the given [`Reflect`] object.
///
/// See [`GetPath::reflect_path`] for more details,
/// see [`element`](Self::element) if you want a typed return value.
fn reflect_element(self, root: &dyn Reflect) -> PathResult<'a, &dyn Reflect>;

/// Gets a mutable reference to the specified element on the given [`Reflect`] object.
///
/// See [`GetPath::reflect_path_mut`] for more details.
fn reflect_element_mut(self, root: &mut dyn Reflect) -> PathResult<'a, &mut dyn Reflect>;

/// Gets a `&T` to the specified element on the given [`Reflect`] object.
///
/// See [`GetPath::path`] for more details.
fn element<T: Reflect>(self, root: &dyn Reflect) -> PathResult<'a, &T> {
self.reflect_element(root).and_then(|p| {
p.downcast_ref::<T>()
.ok_or(ReflectPathError::InvalidDowncast)
})
}

/// Gets a `&mut T` to the specified element on the given [`Reflect`] object.
///
/// See [`GetPath::path_mut`] for more details.
fn element_mut<T: Reflect>(self, root: &mut dyn Reflect) -> PathResult<'a, &mut T> {
self.reflect_element_mut(root).and_then(|p| {
p.downcast_mut::<T>()
.ok_or(ReflectPathError::InvalidDowncast)
})
}
}
impl<'a> ReflectPath<'a> for &'a str {
fn reflect_element(self, mut root: &dyn Reflect) -> PathResult<'a, &dyn Reflect> {
for (access, offset) in PathParser::new(self) {
root = access?.element(root, offset)?;
}
Ok(root)
}
fn reflect_element_mut(self, mut root: &mut dyn Reflect) -> PathResult<'a, &mut dyn Reflect> {
for (access, offset) in PathParser::new(self) {
root = access?.element_mut(root, offset)?;
}
Ok(root)
}
}
/// A trait which allows nested [`Reflect`] values to be retrieved with path strings.
///
/// Using these functions repeatedly with the same string requires parsing the string every time.
Expand Down Expand Up @@ -176,21 +225,25 @@ pub enum ReflectPathError<'a> {
/// [`List`]: crate::List
/// [`Array`]: crate::Array
/// [`Enum`]: crate::Enum
pub trait GetPath {
pub trait GetPath: Reflect {
/// Returns a reference to the value specified by `path`.
///
/// To retrieve a statically typed reference, use
/// [`path`][GetPath::path].
fn reflect_path<'p>(&self, path: &'p str) -> Result<&dyn Reflect, ReflectPathError<'p>>;
fn reflect_path<'p>(&self, path: impl ReflectPath<'p>) -> PathResult<'p, &dyn Reflect> {
path.reflect_element(self.as_reflect())
}

/// Returns a mutable reference to the value specified by `path`.
///
/// To retrieve a statically typed mutable reference, use
/// [`path_mut`][GetPath::path_mut].
fn reflect_path_mut<'p>(
&mut self,
path: &'p str,
) -> Result<&mut dyn Reflect, ReflectPathError<'p>>;
path: impl ReflectPath<'p>,
) -> PathResult<'p, &mut dyn Reflect> {
path.reflect_element_mut(self.as_reflect_mut())
}

/// Returns a statically typed reference to the value specified by `path`.
///
Expand All @@ -199,11 +252,8 @@ pub trait GetPath {
/// (which may be the case when using dynamic types like [`DynamicStruct`]).
///
/// [`DynamicStruct`]: crate::DynamicStruct
fn path<'p, T: Reflect>(&self, path: &'p str) -> Result<&T, ReflectPathError<'p>> {
self.reflect_path(path).and_then(|p| {
p.downcast_ref::<T>()
.ok_or(ReflectPathError::InvalidDowncast)
})
fn path<'p, T: Reflect>(&self, path: impl ReflectPath<'p>) -> PathResult<'p, &T> {
path.element(self.as_reflect())
}

/// Returns a statically typed mutable reference to the value specified by `path`.
Expand All @@ -213,47 +263,13 @@ pub trait GetPath {
/// (which may be the case when using dynamic types like [`DynamicStruct`]).
///
/// [`DynamicStruct`]: crate::DynamicStruct
fn path_mut<'p, T: Reflect>(&mut self, path: &'p str) -> Result<&mut T, ReflectPathError<'p>> {
self.reflect_path_mut(path).and_then(|p| {
p.downcast_mut::<T>()
.ok_or(ReflectPathError::InvalidDowncast)
})
}
}

impl<T: Reflect> GetPath for T {
fn reflect_path<'p>(&self, path: &'p str) -> Result<&dyn Reflect, ReflectPathError<'p>> {
(self as &dyn Reflect).reflect_path(path)
}

fn reflect_path_mut<'p>(
&mut self,
path: &'p str,
) -> Result<&mut dyn Reflect, ReflectPathError<'p>> {
(self as &mut dyn Reflect).reflect_path_mut(path)
fn path_mut<'p, T: Reflect>(&mut self, path: impl ReflectPath<'p>) -> PathResult<'p, &mut T> {
path.element_mut(self.as_reflect_mut())
}
}

impl GetPath for dyn Reflect {
fn reflect_path<'p>(&self, path: &'p str) -> Result<&dyn Reflect, ReflectPathError<'p>> {
let mut current: &dyn Reflect = self;
for (access, offset) in PathParser::new(path) {
current = access?.element(current, offset)?;
}
Ok(current)
}

fn reflect_path_mut<'p>(
&mut self,
path: &'p str,
) -> Result<&mut dyn Reflect, ReflectPathError<'p>> {
let mut current: &mut dyn Reflect = self;
for (access, offset) in PathParser::new(path) {
current = access?.element_mut(current, offset)?;
}
Ok(current)
}
}
// Implement `GetPath` for `dyn Reflect`
impl<T: Reflect + ?Sized> GetPath for T {}

/// A pre-parsed path to an element within a type.
///
Expand Down Expand Up @@ -288,7 +304,7 @@ impl ParsedPath {
///
/// # Example
/// ```
/// # use bevy_reflect::{ParsedPath, Reflect};
/// # use bevy_reflect::{ParsedPath, Reflect, ReflectPath};
/// #[derive(Reflect)]
/// struct Foo {
/// bar: Bar,
Expand Down Expand Up @@ -319,7 +335,7 @@ impl ParsedPath {
/// assert_eq!(parsed_path.element::<u32>(&foo).unwrap(), &123);
/// ```
///
pub fn parse(string: &str) -> Result<Self, ReflectPathError<'_>> {
pub fn parse(string: &str) -> PathResult<Self> {
let mut parts = Vec::new();
for (access, offset) in PathParser::new(string) {
parts.push((access?.into_owned(), offset));
Expand All @@ -329,74 +345,26 @@ impl ParsedPath {

/// Similar to [`Self::parse`] but only works on `&'static str`
/// and does not allocate per named field.
pub fn parse_static(string: &'static str) -> Result<Self, ReflectPathError<'_>> {
pub fn parse_static(string: &'static str) -> PathResult<Self> {
let mut parts = Vec::new();
for (access, offset) in PathParser::new(string) {
parts.push((access?, offset));
}
Ok(Self(parts.into_boxed_slice()))
}

/// Gets a read-only reference to the specified element on the given [`Reflect`] object.
///
/// Returns an error if the path is invalid for the provided type.
///
/// See [`element_mut`](Self::reflect_element_mut) for a typed version of this method.
pub fn reflect_element<'r, 'p>(
&'p self,
root: &'r dyn Reflect,
) -> Result<&'r dyn Reflect, ReflectPathError<'p>> {
let mut current = root;
for (access, offset) in self.0.iter() {
current = access.element(current, *offset)?;
}
impl<'a> ReflectPath<'a> for &'a ParsedPath {
fn reflect_element(self, mut root: &dyn Reflect) -> PathResult<'a, &dyn Reflect> {
for (access, offset) in &*self.0 {
root = access.element(root, *offset)?;
}
Ok(current)
Ok(root)
}

/// Gets a mutable reference to the specified element on the given [`Reflect`] object.
///
/// Returns an error if the path is invalid for the provided type.
///
/// See [`element_mut`](Self::element_mut) for a typed version of this method.
pub fn reflect_element_mut<'r, 'p>(
&'p self,
root: &'r mut dyn Reflect,
) -> Result<&'r mut dyn Reflect, ReflectPathError<'p>> {
let mut current = root;
for (access, offset) in self.0.iter() {
current = access.element_mut(current, *offset)?;
fn reflect_element_mut(self, mut root: &mut dyn Reflect) -> PathResult<'a, &mut dyn Reflect> {
for (access, offset) in &*self.0 {
root = access.element_mut(root, *offset)?;
}
Ok(current)
}

/// Gets a typed, read-only reference to the specified element on the given [`Reflect`] object.
///
/// Returns an error if the path is invalid for the provided type.
///
/// See [`reflect_element`](Self::reflect_element) for an untyped version of this method.
pub fn element<'r, 'p, T: Reflect>(
&'p self,
root: &'r dyn Reflect,
) -> Result<&'r T, ReflectPathError<'p>> {
self.reflect_element(root).and_then(|p| {
p.downcast_ref::<T>()
.ok_or(ReflectPathError::InvalidDowncast)
})
}

/// Gets a typed, read-only reference to the specified element on the given [`Reflect`] object.
///
/// Returns an error if the path is invalid for the provided type.
///
/// See [`reflect_element_mut`](Self::reflect_element_mut) for an untyped version of this method.
pub fn element_mut<'r, 'p, T: Reflect>(
&'p self,
root: &'r mut dyn Reflect,
) -> Result<&'r mut T, ReflectPathError<'p>> {
self.reflect_element_mut(root).and_then(|p| {
p.downcast_mut::<T>()
.ok_or(ReflectPathError::InvalidDowncast)
})
Ok(root)
}
}

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