# Objective
Fixes#8965.
#### Background
For convenience and to ensure everything is setup properly, we
automatically add certain bounds to the derived types. The current
implementation does this by taking the types from all active fields and
adding them to the where-clause of the generated impls. I believe this
method was chosen because it won't add bounds to types that are
otherwise ignored.
```rust
#[derive(Reflect)]
struct Foo<T, U: SomeTrait, V> {
t: T,
u: U::Assoc,
#[reflect(ignore)]
v: [V; 2]
}
// Generates something like:
impl<T, U: SomeTrait, V> for Foo<T, U, V>
where
// Active:
T: Reflect,
U::Assoc: Reflect,
// Ignored:
[V; 2]: Send + Sync + Any
{
// ...
}
```
The self-referential type fails because it ends up using _itself_ as a
type bound due to being one of its own active fields.
```rust
#[derive(Reflect)]
struct Foo {
foo: Vec<Foo>
}
// Foo where Vec<Foo>: Reflect -> Vec<T> where T: Reflect -> Foo where Vec<Foo>: Reflect -> ...
```
## Solution
We can't simply parse all field types for the name of our type. That
would be both complex and prone to errors and false-positives. And even
if it wasn't, what would we replace the bound with?
Instead, I opted to go for a solution that only adds the bounds to what
really needs it: the type parameters. While the bounds on concrete types
make errors a bit cleaner, they aren't strictly necessary. This means we
can change our generated where-clause to only add bounds to generic type
parameters.
Doing this, though, returns us back to the problem of over-bounding
parameters that don't need to be bounded. To solve this, I added a new
container attribute (based on
[this](https://github.com/dtolnay/syn/issues/422#issuecomment-406882925)
comment and @nicopap's
[comment](https://github.com/bevyengine/bevy/pull/9046#issuecomment-1623593780))
that allows us to pass in a custom where clause to modify what bounds
are added to these type parameters.
This allows us to do stuff like:
```rust
trait Trait {
type Assoc;
}
// We don't need `T` to be reflectable since we only care about `T::Assoc`.
#[derive(Reflect)]
#[reflect(where T::Assoc: FromReflect)]
struct Foo<T: Trait>(T::Assoc);
#[derive(TypePath)]
struct Bar;
impl Trait for Bar {
type Assoc = usize;
}
#[derive(Reflect)]
struct Baz {
a: Foo<Bar>,
}
```
> **Note**
> I also
[tried](dc139ea34c)
allowing `#[reflect(ignore)]` to be used on the type parameters
themselves, but that proved problematic since the derive macro does not
consume the attribute. This is why I went with the container attribute
approach.
### Alternatives
One alternative could possibly be to just not add reflection bounds
automatically (i.e. only add required bounds like `Send`, `Sync`, `Any`,
and `TypePath`).
The downside here is we add more friction to using reflection, which
already comes with its own set of considerations. This is a potentially
viable option, but we really need to consider whether or not the
ergonomics hit is worth it.
If we did decide to go the more manual route, we should at least
consider something like #5772 to make it easier for users to add the
right bounds (although, this could still become tricky with
`FromReflect` also being automatically derived).
### Open Questions
1. Should we go with this approach or the manual alternative?
2. ~~Should we add a `skip_params` attribute to avoid the `T: 'static`
trick?~~ ~~Decided to go with `custom_where()` as it's the simplest~~
Scratch that, went with a normal where clause
3. ~~`custom_where` bikeshedding?~~ No longer needed since we are using
a normal where clause
### TODO
- [x] Add compile-fail tests
---
## Changelog
- Fixed issue preventing recursive types from deriving `Reflect`
- Changed how where-clause bounds are generated by the `Reflect` derive
macro
- They are now only applied to the type parameters, not to all active
fields
- Added `#[reflect(where T: Trait, U::Assoc: Trait, ...)]` container
attribute
## Migration Guide
When deriving `Reflect`, generic type params that do not need the
automatic reflection bounds (such as `Reflect`) applied to them will
need to opt-out using a custom where clause like: `#[reflect(where T:
Trait, U::Assoc: Trait, ...)]`.
The attribute can define custom bounds only used by the reflection
impls. To simply opt-out all the type params, we can pass in an empty
where clause: `#[reflect(where)]`.
```rust
// BEFORE:
#[derive(Reflect)]
struct Foo<T>(#[reflect(ignore)] T);
// AFTER:
#[derive(Reflect)]
#[reflect(where)]
struct Foo<T>(#[reflect(ignore)] T);
```
---------
Co-authored-by: Nicola Papale <nicopap@users.noreply.github.com>
# Objective
- Implement common traits on primitives
## Solution
- Derive PartialEq on types that were missing it.
- Derive Copy on small types that were missing it.
- Derive Serialize/Deserialize if the feature on bevy_math is enabled.
- Add a lot of cursed stuff to the bevy_reflect `impls` module.
# Objective
- Address junk leftover by TypeUuid removal
## Solution
- Get rid of unused deps and imports
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
TypeUuid is deprecated, remove it.
## Migration Guide
Convert any uses of `#[derive(TypeUuid)]` with `#[derive(TypePath]` for
more complex uses see the relevant
[documentation](https://docs.rs/bevy/latest/bevy/prelude/trait.TypePath.html)
for more information.
---------
Co-authored-by: ebola <dev@axiomatic>
# Objective
- Extend reflection to the standard library's `Wrapping` and
`Saturating` generic types.
This wasn't my use-case but someone in the discord was surprised that
this wasn't already done. I decided to make a PR because the other
`std::num` items were reflected and if there's a reason to exclude
`Wrapping` and `Saturating`, I am unaware of it.
## Solution
Trivial fix
---
## Changelog
Implemented `Reflect` for `Wrapping<T>` and `Saturating<T>` from
`std::num`.
# Objective
- Tests are manually checking whether derived types implement certain
traits. (Specifically in `bevy_reflect.)
- #11182 introduces
[`static_assertions`](https://docs.rs/static_assertions/) to
automatically check this.
- Simplifies `Reflect` test in #11195.
- Closes#11196.
## Solution
- Add `static_assertions` and replace current tests.
---
I wasn't sure whether to remove the existing test or not. What do you
think?
Update to `glam` 0.25, `encase` 0.7 and `hexasphere` to 10.0
## Changelog
Added the `FloatExt` trait to the `bevy_math` prelude which adds `lerp`,
`inverse_lerp` and `remap` methods to the `f32` and `f64` types.
# Objective
- Fix#11117 by implementing `Reflect` for `EntityHashMap`
## Solution
- By implementing `TypePath` for `EntityHash`, Bevy will automatically
implement `Reflect` for `EntityHashMap`
---
## Changelog
- `TypePath` is implemented for `EntityHash`
- A test called `entity_hashmap_should_impl_reflect` was created to
verify that #11117 was solved.
# Objective
There are a lot of doctests that are `ignore`d for no documented reason.
And that should be fixed.
## Solution
I searched the bevy repo with the regex ` ```[a-z,]*ignore ` in order to
find all `ignore`d doctests. For each one of the `ignore`d doctests, I
did the following steps:
1. Attempt to remove the `ignored` attribute while still passing the
test. I did this by adding hidden dummy structs and imports.
2. If step 1 doesn't work, attempt to replace the `ignored` attribute
with the `no_run` attribute while still passing the test.
3. If step 2 doesn't work, keep the `ignored` attribute but add
documentation for why the `ignored` attribute was added.
---------
Co-authored-by: François <mockersf@gmail.com>
# Objective
Fix ci hang, so we can merge pr's again.
## Solution
- switch ppa action to use mesa stable versions
https://launchpad.net/~kisak/+archive/ubuntu/turtle
- use commit from #11123
---------
Co-authored-by: Stepan Koltsov <stepan.koltsov@gmail.com>
# Objective
- Provides an alternate solution to the one implemented in #10791
without breaking changes.
## Solution
- Changes the bounds of macro-generated `TypePath` implementations to
universally ignore the types of fields, rather than use the same bounds
as other implementations. I think this is a more holistic solution than
#10791 because it totally erases the finicky bounds we currently
generate, helping to untangle the reflection trait system.
# Objective
- Make the implementation order consistent between all sources to fit
the order in the trait.
## Solution
- Change the implementation order.
Matches versioning & features from other Cargo.toml files in the
project.
# Objective
Resolves#10932
## Solution
Added smallvec to the bevy_utils cargo.toml and added a line to
re-export the crate. Target version and features set to match what's
used in the other bevy crates.
# Objective
Printing `DynamicStruct` with a debug format does not show the contained
type anymore. For instance, in `examples/reflection/reflection.rs`,
adding `dbg!(&reflect_value);` to line 96 will print:
```rust
[examples/reflection/reflection.rs:96] &reflect_value = DynamicStruct(bevy_reflect::DynamicStruct {
a: 4,
nested: DynamicStruct(bevy_reflect::DynamicStruct {
b: 8,
}),
})
```
## Solution
Show the represented type instead (`reflection::Foo` and
`reflection::Bar` in this case):
```rust
[examples/reflection/reflection.rs:96] &reflect_value = DynamicStruct(reflection::Foo {
a: 4,
nested: DynamicStruct(reflection::Bar {
b: 8,
}),
})
```
---------
Co-authored-by: Gino Valente <49806985+MrGVSV@users.noreply.github.com>
# Objective
> Issue raised on
[Discord](https://discord.com/channels/691052431525675048/1002362493634629796/1179182488787103776)
Currently the following code fails due to a missing `TypePath` bound:
```rust
#[derive(Reflect)] struct Foo<T>(T);
#[derive(Reflect)] struct Bar<T>(Foo<T>);
#[derive(Reflect)] struct Baz<T>(Bar<Foo<T>>);
```
## Solution
Add `TypePath` to the per-field bounds instead of _just_ the generic
type parameter bounds.
### Related Work
It should be noted that #9046 would help make these kinds of issues
easier to work around and/or avoid entirely.
---
## Changelog
- Fixes missing `TypePath` requirement when deriving `Reflect` on nested
generics
# Objective
- Shorten paths by removing unnecessary prefixes
## Solution
- Remove the prefixes from many paths which do not need them. Finding
the paths was done automatically using built-in refactoring tools in
Jetbrains RustRover.
# Objective
Related to #10612.
Enable the
[`clippy::manual_let_else`](https://rust-lang.github.io/rust-clippy/master/#manual_let_else)
lint as a warning. The `let else` form seems more idiomatic to me than a
`match`/`if else` that either match a pattern or diverge, and from the
clippy doc, the lint doesn't seem to have any possible false positive.
## Solution
Add the lint as warning in `Cargo.toml`, refactor places where the lint
triggers.
# Objective
The `generate_composite_uuid` utility function hidden in
`bevy_reflect::__macro_exports` could be generally useful to users.
For example, I previously relied on `Hash` to generate a `u64` to create
a deterministic `HandleId`. In v0.12, `HandleId` has been replaced by
`AssetId` which now requires a `Uuid`, which I could generate with this
function.
## Solution
Relocate `generate_composite_uuid` from `bevy_reflect::__macro_exports`
to `bevy_utils::uuid`.
It is still re-exported under `bevy_reflect::__macro_exports` so there
should not be any breaking changes (although, users should generally not
rely on pseudo-private/hidden modules like `__macro_exports`).
I chose to keep it in `bevy_reflect::__macro_exports` so as to not
clutter up our public API and to reduce the number of changes in this
PR. We could have also marked the export as `#[doc(hidden)]`, but
personally I like that we have a dedicated module for this (makes it
clear what is public and what isn't when just looking at the macro
code).
---
## Changelog
- Moved `generate_composite_uuid` to `bevy_utils::uuid` and made it
public
- Note: it was technically already public, just hidden
# Objective
- Fix#10499
## Solution
- Use `.get_represented_type_info()` module path and type ident instead
of `.reflect_*` module path and type ident when serializing the `Option`
enum
---
## Changelog
- Fix serialization bug
- Add simple test
- Add `serde_json` dev dependency
- Add `serde` with `derive` feature dev dependency (wouldn't compile for
me without it)
---------
Co-authored-by: hank <hank@hank.co.in>
Co-authored-by: Gino Valente <49806985+MrGVSV@users.noreply.github.com>
# Objective
- Standardize fmt for toml files
## Solution
- Add [taplo](https://taplo.tamasfe.dev/) to CI (check for fmt and diff
for toml files), for context taplo is used by the most popular extension
in VScode [Even Better
TOML](https://marketplace.visualstudio.com/items?itemName=tamasfe.even-better-toml
- Add contribution section to explain toml fmt with taplo.
Now to pass CI you need to run `taplo fmt --option indent_string=" "` or
if you use vscode have the `Even Better TOML` extension with 4 spaces
for indent
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
- Fix adding `#![allow(clippy::type_complexity)]` everywhere. like #9796
## Solution
- Use the new [lints] table that will land in 1.74
(https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#lints)
- inherit lint to the workspace, crates and examples.
```
[lints]
workspace = true
```
## Changelog
- Bump rust version to 1.74
- Enable lints table for the workspace
```toml
[workspace.lints.clippy]
type_complexity = "allow"
```
- Allow type complexity for all crates and examples
```toml
[lints]
workspace = true
```
---------
Co-authored-by: Martín Maita <47983254+mnmaita@users.noreply.github.com>
Preparing next release
This PR has been auto-generated
---------
Co-authored-by: Bevy Auto Releaser <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: François <mockersf@gmail.com>
# Objective
Fixes#5101
Alternative to #6511
## Solution
Corrected the behavior for ignored fields in `FromReflect`, which was
previously using the incorrect field indexes.
Similarly, fields marked with `#[reflect(skip_serializing)]` no longer
break when using `FromReflect` after deserialization. This was done by
modifying `SerializationData` to store a function pointer that can later
be used to generate a default instance of the skipped field during
deserialization.
The function pointer points to a function generated by the derive macro
using the behavior designated by `#[reflect(default)]` (or just
`Default` if none provided). The entire output of the macro is now
wrapped in an [unnamed
constant](https://doc.rust-lang.org/stable/reference/items/constant-items.html#unnamed-constant)
which keeps this behavior hygienic.
#### Rationale
The biggest downside to this approach is that it requires fields marked
`#[reflect(skip_serializing)]` to provide the ability to create a
default instance— either via a `Default` impl or by specifying a custom
one. While this isn't great, I think it might be justified by the fact
that we really need to create this value when using `FromReflect` on a
deserialized object. And we need to do this _during_ deserialization
because after that (at least for tuples and tuple structs) we lose
information about which field is which: _"is the value at index 1 in
this `DynamicTupleStruct` the actual value for index 1 or is it really
the value for index 2 since index 1 is skippable...?"_
#### Alternatives
An alternative would be to store `Option<Box<dyn Reflect>>` within
`DynamicTuple` and `DynamicTupleStruct` instead of just `Box<dyn
Reflect>`. This would allow us to insert "empty"/"missing" fields during
deserialization, thus saving the positional information of the skipped
fields. However, this may require changing the API of `Tuple` and
`TupleStruct` such that they can account for their dynamic counterparts
returning `None` for a skipped field. In practice this would probably
mean exposing the `Option`-ness of the dynamics onto implementors via
methods like `Tuple::drain` or `TupleStruct::field`.
Personally, I think requiring `Default` would be better than muddying up
the API to account for these special cases. But I'm open to trying out
this other approach if the community feels that it's better.
---
## Changelog
### Public Changes
#### Fixed
- The behaviors of `#[reflect(ignore)]` and
`#[reflect(skip_serializing)]` are no longer dependent on field order
#### Changed
- Fields marked with `#[reflect(skip_serializing)]` now need to either
implement `Default` or specify a custom default function using
`#[reflect(default = "path::to::some_func")]`
- Deserializing a type with fields marked `#[reflect(skip_serializing)]`
will now include that field initialized to its specified default value
- `SerializationData::new` now takes the new `SkippedField` struct along
with the skipped field index
- Renamed `SerializationData::is_ignored_field` to
`SerializationData::is_field_skipped`
#### Added
- Added `SkippedField` struct
- Added methods `SerializationData::generate_default` and
`SerializationData::iter_skipped`
### Internal Changes
#### Changed
- Replaced `members_to_serialization_denylist` and `BitSet<u32>` with
`SerializationDataDef`
- The `Reflect` derive is more hygienic as it now outputs within an
[unnamed
constant](https://doc.rust-lang.org/stable/reference/items/constant-items.html#unnamed-constant)
- `StructField::index` has been split up into
`StructField::declaration_index` and `StructField::reflection_index`
#### Removed
- Removed `bitset` dependency
## Migration Guide
* Fields marked `#[reflect(skip_serializing)]` now must implement
`Default` or specify a custom default function with `#[reflect(default =
"path::to::some_func")]`
```rust
#[derive(Reflect)]
struct MyStruct {
#[reflect(skip_serializing)]
#[reflect(default = "get_foo_default")]
foo: Foo, // <- `Foo` does not impl `Default` so requires a custom
function
#[reflect(skip_serializing)]
bar: Bar, // <- `Bar` impls `Default`
}
#[derive(Reflect)]
struct Foo(i32);
#[derive(Reflect, Default)]
struct Bar(i32);
fn get_foo_default() -> Foo {
Foo(123)
}
```
* `SerializationData::new` has been changed to expect an iterator of
`(usize, SkippedField)` rather than one of just `usize`
```rust
// BEFORE
SerializationData::new([0, 3].into_iter());
// AFTER
SerializationData::new([
(0, SkippedField::new(field_0_default_fn)),
(3, SkippedField::new(field_3_default_fn)),
].into_iter());
```
* `Serialization::is_ignored_field` has been renamed to
`Serialization::is_field_skipped`
* Fields marked `#[reflect(skip_serializing)]` are now included in
deserialization output. This may affect logic that expected those fields
to be absent.
# Objective
Fixes#10086
## Solution
Instead of serializing via `DynamicTypePath::reflect_type_path`, now
uses the `TypePath` found on the `TypeInfo` returned by
`Reflect::get_represented_type_info`.
This issue was happening because the dynamic types implement `TypePath`
themselves and do not (and cannot) forward their proxy's `TypePath`
data. The solution was to access the proxy's type information in order
to get the correct `TypePath` data.
## Changed
- The `Debug` impl for `TypePathTable` now includes output for all
fields.
# Objective
- Fixes#8303
## Solution
- Replaced 1 instance of `OnceBox<T>` with `OnceLock<T>` in
`NonGenericTypeCell`
## Notes
All changes are in the private side of Bevy, and appear to have no
observable change in performance or compilation time. This is purely to
reduce the quantity of direct dependencies in Bevy.
Adopted from #8954, co-authored by @pyrotechnick
# Objective
The Bevy ecosystem currently reflects `Quat` via "value" rather than the
more appropriate "struct" strategy. This behaviour is inconsistent to
that of similar types, i.e. `Vec3`. Additionally, employing the "value"
strategy causes instances of `Quat` to be serialised as a sequence `[x,
y, z, w]` rather than structures of shape `{ x, y, z, w }`.
The [comments surrounding the applicable
code](bec299fa6e/crates/bevy_reflect/src/impls/glam.rs (L254))
give context and historical reasons for this discrepancy:
```
// Quat fields are read-only (as of now), and reflection is currently missing
// mechanisms for read-only fields. I doubt those mechanisms would be added,
// so for now quaternions will remain as values. They are represented identically
// to Vec4 and DVec4, so you may use those instead and convert between.
```
This limitation has [since been lifted by the upstream
crate](374625163e),
glam.
## Solution
Migrating the reflect strategy of Quat from "value" to "struct" via
replacing `impl_reflect_value` with `impl_reflect_struct` resolves the
issue.
## Changelog
Migrated `Quat` reflection strategy to "struct" from "value"
Migration Guide
Changed Quat serialization/deserialization from sequences `[x, y, z, w]`
to structures `{ x, y, z, w }`.
---------
Co-authored-by: pyrotechnick <13998+pyrotechnick@users.noreply.github.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
- Followup to #7184.
- ~Deprecate `TypeUuid` and remove its internal references.~ No longer
part of this PR.
- Use `TypePath` for the type registry, and (de)serialisation instead of
`std::any::type_name`.
- Allow accessing type path information behind proxies.
## Solution
- Introduce methods on `TypeInfo` and friends for dynamically querying
type path. These methods supersede the old `type_name` methods.
- Remove `Reflect::type_name` in favor of `DynamicTypePath::type_path`
and `TypeInfo::type_path_table`.
- Switch all uses of `std::any::type_name` in reflection, non-debugging
contexts to use `TypePath`.
---
## Changelog
- Added `TypePathTable` for dynamically accessing methods on `TypePath`
through `TypeInfo` and the type registry.
- Removed `type_name` from all `TypeInfo`-like structs.
- Added `type_path` and `type_path_table` methods to all `TypeInfo`-like
structs.
- Removed `Reflect::type_name` in favor of
`DynamicTypePath::reflect_type_path` and `TypeInfo::type_path`.
- Changed the signature of all `DynamicTypePath` methods to return
strings with a static lifetime.
## Migration Guide
- Rely on `TypePath` instead of `std::any::type_name` for all stability
guarantees and for use in all reflection contexts, this is used through
with one of the following APIs:
- `TypePath::type_path` if you have a concrete type and not a value.
- `DynamicTypePath::reflect_type_path` if you have an `dyn Reflect`
value without a concrete type.
- `TypeInfo::type_path` for use through the registry or if you want to
work with the represented type of a `DynamicFoo`.
- Remove `type_name` from manual `Reflect` implementations.
- Use `type_path` and `type_path_table` in place of `type_name` on
`TypeInfo`-like structs.
- Use `get_with_type_path(_mut)` over `get_with_type_name(_mut)`.
## Note to reviewers
I think if anything we were a little overzealous in merging #7184 and we
should take that extra care here.
In my mind, this is the "point of no return" for `TypePath` and while I
think we all agree on the design, we should carefully consider if the
finer details and current implementations are actually how we want them
moving forward.
For example [this incorrect `TypePath` implementation for
`String`](3fea3c6c0b/crates/bevy_reflect/src/impls/std.rs (L90))
(note that `String` is in the default Rust prelude) snuck in completely
under the radar.
# Objective
- Updates for rust 1.73
## Solution
- new doc check for `redundant_explicit_links`
- updated to text for compile fail tests
---
## Changelog
- updates for rust 1.73
# Objective
- Fixes#4610
## Solution
- Replaced all instances of `parking_lot` locks with equivalents from
`std::sync`. Acquiring locks within `std::sync` can fail, so
`.expect("Lock Poisoned")` statements were added where required.
## Comments
In [this
comment](https://github.com/bevyengine/bevy/issues/4610#issuecomment-1592407881),
the lack of deadlock detection was mentioned as a potential reason to
not make this change. From what I can gather, Bevy doesn't appear to be
using this functionality within the engine. Unless it was expected that
a Bevy consumer was expected to enable and use this functionality, it
appears to be a feature lost without consequence.
Unfortunately, `cpal` and `wgpu` both still rely on `parking_lot`,
leaving it in the dependency graph even after this change.
From my basic experimentation, this change doesn't appear to have any
performance impacts, positive or negative. I tested this using
`bevymark` with 50,000 entities and observed 20ms of frame-time before
and after the change. More extensive testing with larger/real projects
should probably be done.
# Objective
- Fixes#9363
## Solution
Moved `fq_std` from `bevy_reflect_derive` to `bevy_macro_utils`. This
does make the `FQ*` types public where they were previously private,
which is a change to the public-facing API, but I don't believe a
breaking one. Additionally, I've done a basic QA pass over the
`bevy_macro_utils` crate, adding `deny(unsafe)`, `warn(missing_docs)`,
and documentation where required.
# Objective
In order to derive `Asset`s (v2), `TypePath` must also be implemented.
`TypePath` is not currently in the prelude, but given it is *required*
when deriving something that *is* in the prelude, I think it deserves to
be added.
## Solution
Add `TypePath` to `bevy_reflect::prelude`.
# Objective
Replace instances of
```rust
for x in collection.iter{_mut}() {
```
with
```rust
for x in &{mut} collection {
```
This also changes CI to no longer suppress this lint. Note that since
this lint only shows up when using clippy in pedantic mode, it was
probably unnecessary to suppress this lint in the first place.
# Objective
The reasoning is similar to #8687.
I'm building a dynamic query. Currently, I store the ReflectFromPtr in
my dynamic `Fetch` type.
[See relevant
code](97ba68ae1e/src/fetches.rs (L14-L17))
However, `ReflectFromPtr` is:
- 16 bytes for TypeId
- 8 bytes for the non-mutable function pointer
- 8 bytes for the mutable function pointer
It's a lot, it adds 32 bytes to my base `Fetch` which is only
`ComponendId` (8 bytes) for a total of 40 bytes.
I only need one function per fetch, reducing the total dynamic fetch
size to 16 bytes.
Since I'm querying the components by the ComponendId associated with the
function pointer I'm using, I don't need the TypeId, it's a redundant
check.
In fact, I've difficulties coming up with situations where checking the
TypeId beforehand is relevant. So to me, if ReflectFromPtr makes sense
as a public API, exposing the function pointers also makes sense.
## Solution
- Make the fields public through methods.
---
## Changelog
- Add `from_ptr` and `from_ptr_mut` methods to `ReflectFromPtr` to
access the underlying function pointers
- `ReflectFromPtr::as_reflect_ptr` is now `ReflectFromPtr::as_reflect`
- `ReflectFromPtr::as_reflect_ptr_mut` is now
`ReflectFromPtr::as_reflect_mut`
## Migration guide
- `ReflectFromPtr::as_reflect_ptr` is now `ReflectFromPtr::as_reflect`
- `ReflectFromPtr::as_reflect_ptr_mut` is now
`ReflectFromPtr::as_reflect_mut`
# Bevy Asset V2 Proposal
## Why Does Bevy Need A New Asset System?
Asset pipelines are a central part of the gamedev process. Bevy's
current asset system is missing a number of features that make it
non-viable for many classes of gamedev. After plenty of discussions and
[a long community feedback
period](https://github.com/bevyengine/bevy/discussions/3972), we've
identified a number missing features:
* **Asset Preprocessing**: it should be possible to "preprocess" /
"compile" / "crunch" assets at "development time" rather than when the
game starts up. This enables offloading expensive work from deployed
apps, faster asset loading, less runtime memory usage, etc.
* **Per-Asset Loader Settings**: Individual assets cannot define their
own loaders that override the defaults. Additionally, they cannot
provide per-asset settings to their loaders. This is a huge limitation,
as many asset types don't provide all information necessary for Bevy
_inside_ the asset. For example, a raw PNG image says nothing about how
it should be sampled (ex: linear vs nearest).
* **Asset `.meta` files**: assets should have configuration files stored
adjacent to the asset in question, which allows the user to configure
asset-type-specific settings. These settings should be accessible during
the pre-processing phase. Modifying a `.meta` file should trigger a
re-processing / re-load of the asset. It should be possible to configure
asset loaders from the meta file.
* **Processed Asset Hot Reloading**: Changes to processed assets (or
their dependencies) should result in re-processing them and re-loading
the results in live Bevy Apps.
* **Asset Dependency Tracking**: The current bevy_asset has no good way
to wait for asset dependencies to load. It punts this as an exercise for
consumers of the loader apis, which is unreasonable and error prone.
There should be easy, ergonomic ways to wait for assets to load and
block some logic on an asset's entire dependency tree loading.
* **Runtime Asset Loading**: it should be (optionally) possible to load
arbitrary assets dynamically at runtime. This necessitates being able to
deploy and run the asset server alongside Bevy Apps on _all platforms_.
For example, we should be able to invoke the shader compiler at runtime,
stream scenes from sources like the internet, etc. To keep deployed
binaries (and startup times) small, the runtime asset server
configuration should be configurable with different settings compared to
the "pre processor asset server".
* **Multiple Backends**: It should be possible to load assets from
arbitrary sources (filesystems, the internet, remote asset serves, etc).
* **Asset Packing**: It should be possible to deploy assets in
compressed "packs", which makes it easier and more efficient to
distribute assets with Bevy Apps.
* **Asset Handoff**: It should be possible to hold a "live" asset
handle, which correlates to runtime data, without actually holding the
asset in memory. Ex: it must be possible to hold a reference to a GPU
mesh generated from a "mesh asset" without keeping the mesh data in CPU
memory
* **Per-Platform Processed Assets**: Different platforms and app
distributions have different capabilities and requirements. Some
platforms need lower asset resolutions or different asset formats to
operate within the hardware constraints of the platform. It should be
possible to define per-platform asset processing profiles. And it should
be possible to deploy only the assets required for a given platform.
These features have architectural implications that are significant
enough to require a full rewrite. The current Bevy Asset implementation
got us this far, but it can take us no farther. This PR defines a brand
new asset system that implements most of these features, while laying
the foundations for the remaining features to be built.
## Bevy Asset V2
Here is a quick overview of the features introduced in this PR.
* **Asset Preprocessing**: Preprocess assets at development time into
more efficient (and configurable) representations
* **Dependency Aware**: Dependencies required to process an asset are
tracked. If an asset's processed dependency changes, it will be
reprocessed
* **Hot Reprocessing/Reloading**: detect changes to asset source files,
reprocess them if they have changed, and then hot-reload them in Bevy
Apps.
* **Only Process Changes**: Assets are only re-processed when their
source file (or meta file) has changed. This uses hashing and timestamps
to avoid processing assets that haven't changed.
* **Transactional and Reliable**: Uses write-ahead logging (a technique
commonly used by databases) to recover from crashes / forced-exits.
Whenever possible it avoids full-reprocessing / only uncompleted
transactions will be reprocessed. When the processor is running in
parallel with a Bevy App, processor asset writes block Bevy App asset
reads. Reading metadata + asset bytes is guaranteed to be transactional
/ correctly paired.
* **Portable / Run anywhere / Database-free**: The processor does not
rely on an in-memory database (although it uses some database techniques
for reliability). This is important because pretty much all in-memory
databases have unsupported platforms or build complications.
* **Configure Processor Defaults Per File Type**: You can say "use this
processor for all files of this type".
* **Custom Processors**: The `Processor` trait is flexible and
unopinionated. It can be implemented by downstream plugins.
* **LoadAndSave Processors**: Most asset processing scenarios can be
expressed as "run AssetLoader A, save the results using AssetSaver X,
and then load the result using AssetLoader B". For example, load this
png image using `PngImageLoader`, which produces an `Image` asset and
then save it using `CompressedImageSaver` (which also produces an
`Image` asset, but in a compressed format), which takes an `Image` asset
as input. This means if you have an `AssetLoader` for an asset, you are
already half way there! It also means that you can share AssetSavers
across multiple loaders. Because `CompressedImageSaver` accepts Bevy's
generic Image asset as input, it means you can also use it with some
future `JpegImageLoader`.
* **Loader and Saver Settings**: Asset Loaders and Savers can now define
their own settings types, which are passed in as input when an asset is
loaded / saved. Each asset can define its own settings.
* **Asset `.meta` files**: configure asset loaders, their settings,
enable/disable processing, and configure processor settings
* **Runtime Asset Dependency Tracking** Runtime asset dependencies (ex:
if an asset contains a `Handle<Image>`) are tracked by the asset server.
An event is emitted when an asset and all of its dependencies have been
loaded
* **Unprocessed Asset Loading**: Assets do not require preprocessing.
They can be loaded directly. A processed asset is just a "normal" asset
with some extra metadata. Asset Loaders don't need to know or care about
whether or not an asset was processed.
* **Async Asset IO**: Asset readers/writers use async non-blocking
interfaces. Note that because Rust doesn't yet support async traits,
there is a bit of manual Boxing / Future boilerplate. This will
hopefully be removed in the near future when Rust gets async traits.
* **Pluggable Asset Readers and Writers**: Arbitrary asset source
readers/writers are supported, both by the processor and the asset
server.
* **Better Asset Handles**
* **Single Arc Tree**: Asset Handles now use a single arc tree that
represents the lifetime of the asset. This makes their implementation
simpler, more efficient, and allows us to cheaply attach metadata to
handles. Ex: the AssetPath of a handle is now directly accessible on the
handle itself!
* **Const Typed Handles**: typed handles can be constructed in a const
context. No more weird "const untyped converted to typed at runtime"
patterns!
* **Handles and Ids are Smaller / Faster To Hash / Compare**: Typed
`Handle<T>` is now much smaller in memory and `AssetId<T>` is even
smaller.
* **Weak Handle Usage Reduction**: In general Handles are now considered
to be "strong". Bevy features that previously used "weak `Handle<T>`"
have been ported to `AssetId<T>`, which makes it statically clear that
the features do not hold strong handles (while retaining strong type
information). Currently Handle::Weak still exists, but it is very
possible that we can remove that entirely.
* **Efficient / Dense Asset Ids**: Assets now have efficient dense
runtime asset ids, which means we can avoid expensive hash lookups.
Assets are stored in Vecs instead of HashMaps. There are now typed and
untyped ids, which means we no longer need to store dynamic type
information in the ID for typed handles. "AssetPathId" (which was a
nightmare from a performance and correctness standpoint) has been
entirely removed in favor of dense ids (which are retrieved for a path
on load)
* **Direct Asset Loading, with Dependency Tracking**: Assets that are
defined at runtime can still have their dependencies tracked by the
Asset Server (ex: if you create a material at runtime, you can still
wait for its textures to load). This is accomplished via the (currently
optional) "asset dependency visitor" trait. This system can also be used
to define a set of assets to load, then wait for those assets to load.
* **Async folder loading**: Folder loading also uses this system and
immediately returns a handle to the LoadedFolder asset, which means
folder loading no longer blocks on directory traversals.
* **Improved Loader Interface**: Loaders now have a specific "top level
asset type", which makes returning the top-level asset simpler and
statically typed.
* **Basic Image Settings and Processing**: Image assets can now be
processed into the gpu-friendly Basic Universal format. The ImageLoader
now has a setting to define what format the image should be loaded as.
Note that this is just a minimal MVP ... plenty of additional work to do
here. To demo this, enable the `basis-universal` feature and turn on
asset processing.
* **Simpler Audio Play / AudioSink API**: Asset handle providers are
cloneable, which means the Audio resource can mint its own handles. This
means you can now do `let sink_handle = audio.play(music)` instead of
`let sink_handle = audio_sinks.get_handle(audio.play(music))`. Note that
this might still be replaced by
https://github.com/bevyengine/bevy/pull/8424.
**Removed Handle Casting From Engine Features**: Ex: FontAtlases no
longer use casting between handle types
## Using The New Asset System
### Normal Unprocessed Asset Loading
By default the `AssetPlugin` does not use processing. It behaves pretty
much the same way as the old system.
If you are defining a custom asset, first derive `Asset`:
```rust
#[derive(Asset)]
struct Thing {
value: String,
}
```
Initialize the asset:
```rust
app.init_asset:<Thing>()
```
Implement a new `AssetLoader` for it:
```rust
#[derive(Default)]
struct ThingLoader;
#[derive(Serialize, Deserialize, Default)]
pub struct ThingSettings {
some_setting: bool,
}
impl AssetLoader for ThingLoader {
type Asset = Thing;
type Settings = ThingSettings;
fn load<'a>(
&'a self,
reader: &'a mut Reader,
settings: &'a ThingSettings,
load_context: &'a mut LoadContext,
) -> BoxedFuture<'a, Result<Thing, anyhow::Error>> {
Box::pin(async move {
let mut bytes = Vec::new();
reader.read_to_end(&mut bytes).await?;
// convert bytes to value somehow
Ok(Thing {
value
})
})
}
fn extensions(&self) -> &[&str] {
&["thing"]
}
}
```
Note that this interface will get much cleaner once Rust gets support
for async traits. `Reader` is an async futures_io::AsyncRead. You can
stream bytes as they come in or read them all into a `Vec<u8>`,
depending on the context. You can use `let handle =
load_context.load(path)` to kick off a dependency load, retrieve a
handle, and register the dependency for the asset.
Then just register the loader in your Bevy app:
```rust
app.init_asset_loader::<ThingLoader>()
```
Now just add your `Thing` asset files into the `assets` folder and load
them like this:
```rust
fn system(asset_server: Res<AssetServer>) {
let handle = Handle<Thing> = asset_server.load("cool.thing");
}
```
You can check load states directly via the asset server:
```rust
if asset_server.load_state(&handle) == LoadState::Loaded { }
```
You can also listen for events:
```rust
fn system(mut events: EventReader<AssetEvent<Thing>>, handle: Res<SomeThingHandle>) {
for event in events.iter() {
if event.is_loaded_with_dependencies(&handle) {
}
}
}
```
Note the new `AssetEvent::LoadedWithDependencies`, which only fires when
the asset is loaded _and_ all dependencies (and their dependencies) have
loaded.
Unlike the old asset system, for a given asset path all `Handle<T>`
values point to the same underlying Arc. This means Handles can cheaply
hold more asset information, such as the AssetPath:
```rust
// prints the AssetPath of the handle
info!("{:?}", handle.path())
```
### Processed Assets
Asset processing can be enabled via the `AssetPlugin`. When developing
Bevy Apps with processed assets, do this:
```rust
app.add_plugins(DefaultPlugins.set(AssetPlugin::processed_dev()))
```
This runs the `AssetProcessor` in the background with hot-reloading. It
reads assets from the `assets` folder, processes them, and writes them
to the `.imported_assets` folder. Asset loads in the Bevy App will wait
for a processed version of the asset to become available. If an asset in
the `assets` folder changes, it will be reprocessed and hot-reloaded in
the Bevy App.
When deploying processed Bevy apps, do this:
```rust
app.add_plugins(DefaultPlugins.set(AssetPlugin::processed()))
```
This does not run the `AssetProcessor` in the background. It behaves
like `AssetPlugin::unprocessed()`, but reads assets from
`.imported_assets`.
When the `AssetProcessor` is running, it will populate sibling `.meta`
files for assets in the `assets` folder. Meta files for assets that do
not have a processor configured look like this:
```rust
(
meta_format_version: "1.0",
asset: Load(
loader: "bevy_render::texture::image_loader::ImageLoader",
settings: (
format: FromExtension,
),
),
)
```
This is metadata for an image asset. For example, if you have
`assets/my_sprite.png`, this could be the metadata stored at
`assets/my_sprite.png.meta`. Meta files are totally optional. If no
metadata exists, the default settings will be used.
In short, this file says "load this asset with the ImageLoader and use
the file extension to determine the image type". This type of meta file
is supported in all AssetPlugin modes. If in `Unprocessed` mode, the
asset (with the meta settings) will be loaded directly. If in
`ProcessedDev` mode, the asset file will be copied directly to the
`.imported_assets` folder. The meta will also be copied directly to the
`.imported_assets` folder, but with one addition:
```rust
(
meta_format_version: "1.0",
processed_info: Some((
hash: 12415480888597742505,
full_hash: 14344495437905856884,
process_dependencies: [],
)),
asset: Load(
loader: "bevy_render::texture::image_loader::ImageLoader",
settings: (
format: FromExtension,
),
),
)
```
`processed_info` contains `hash` (a direct hash of the asset and meta
bytes), `full_hash` (a hash of `hash` and the hashes of all
`process_dependencies`), and `process_dependencies` (the `path` and
`full_hash` of every process_dependency). A "process dependency" is an
asset dependency that is _directly_ used when processing the asset.
Images do not have process dependencies, so this is empty.
When the processor is enabled, you can use the `Process` metadata
config:
```rust
(
meta_format_version: "1.0",
asset: Process(
processor: "bevy_asset::processor::process::LoadAndSave<bevy_render::texture::image_loader::ImageLoader, bevy_render::texture::compressed_image_saver::CompressedImageSaver>",
settings: (
loader_settings: (
format: FromExtension,
),
saver_settings: (
generate_mipmaps: true,
),
),
),
)
```
This configures the asset to use the `LoadAndSave` processor, which runs
an AssetLoader and feeds the result into an AssetSaver (which saves the
given Asset and defines a loader to load it with). (for terseness
LoadAndSave will likely get a shorter/friendlier type name when [Stable
Type Paths](#7184) lands). `LoadAndSave` is likely to be the most common
processor type, but arbitrary processors are supported.
`CompressedImageSaver` saves an `Image` in the Basis Universal format
and configures the ImageLoader to load it as basis universal. The
`AssetProcessor` will read this meta, run it through the LoadAndSave
processor, and write the basis-universal version of the image to
`.imported_assets`. The final metadata will look like this:
```rust
(
meta_format_version: "1.0",
processed_info: Some((
hash: 905599590923828066,
full_hash: 9948823010183819117,
process_dependencies: [],
)),
asset: Load(
loader: "bevy_render::texture::image_loader::ImageLoader",
settings: (
format: Format(Basis),
),
),
)
```
To try basis-universal processing out in Bevy examples, (for example
`sprite.rs`), change `add_plugins(DefaultPlugins)` to
`add_plugins(DefaultPlugins.set(AssetPlugin::processed_dev()))` and run
with the `basis-universal` feature enabled: `cargo run
--features=basis-universal --example sprite`.
To create a custom processor, there are two main paths:
1. Use the `LoadAndSave` processor with an existing `AssetLoader`.
Implement the `AssetSaver` trait, register the processor using
`asset_processor.register_processor::<LoadAndSave<ImageLoader,
CompressedImageSaver>>(image_saver.into())`.
2. Implement the `Process` trait directly and register it using:
`asset_processor.register_processor(thing_processor)`.
You can configure default processors for file extensions like this:
```rust
asset_processor.set_default_processor::<ThingProcessor>("thing")
```
There is one more metadata type to be aware of:
```rust
(
meta_format_version: "1.0",
asset: Ignore,
)
```
This will ignore the asset during processing / prevent it from being
written to `.imported_assets`.
The AssetProcessor stores a transaction log at `.imported_assets/log`
and uses it to gracefully recover from unexpected stops. This means you
can force-quit the processor (and Bevy Apps running the processor in
parallel) at arbitrary times!
`.imported_assets` is "local state". It should _not_ be checked into
source control. It should also be considered "read only". In practice,
you _can_ modify processed assets and processed metadata if you really
need to test something. But those modifications will not be represented
in the hashes of the assets, so the processed state will be "out of
sync" with the source assets. The processor _will not_ fix this for you.
Either revert the change after you have tested it, or delete the
processed files so they can be re-populated.
## Open Questions
There are a number of open questions to be discussed. We should decide
if they need to be addressed in this PR and if so, how we will address
them:
### Implied Dependencies vs Dependency Enumeration
There are currently two ways to populate asset dependencies:
* **Implied via AssetLoaders**: if an AssetLoader loads an asset (and
retrieves a handle), a dependency is added to the list.
* **Explicit via the optional Asset::visit_dependencies**: if
`server.load_asset(my_asset)` is called, it will call
`my_asset.visit_dependencies`, which will grab dependencies that have
been manually defined for the asset via the Asset trait impl (which can
be derived).
This means that defining explicit dependencies is optional for "loaded
assets". And the list of dependencies is always accurate because loaders
can only produce Handles if they register dependencies. If an asset was
loaded with an AssetLoader, it only uses the implied dependencies. If an
asset was created at runtime and added with
`asset_server.load_asset(MyAsset)`, it will use
`Asset::visit_dependencies`.
However this can create a behavior mismatch between loaded assets and
equivalent "created at runtime" assets if `Assets::visit_dependencies`
doesn't exactly match the dependencies produced by the AssetLoader. This
behavior mismatch can be resolved by completely removing "implied loader
dependencies" and requiring `Asset::visit_dependencies` to supply
dependency data. But this creates two problems:
* It makes defining loaded assets harder and more error prone: Devs must
remember to manually annotate asset dependencies with `#[dependency]`
when deriving `Asset`. For more complicated assets (such as scenes), the
derive likely wouldn't be sufficient and a manual `visit_dependencies`
impl would be required.
* Removes the ability to immediately kick off dependency loads: When
AssetLoaders retrieve a Handle, they also immediately kick off an asset
load for the handle, which means it can start loading in parallel
_before_ the asset finishes loading. For large assets, this could be
significant. (although this could be mitigated for processed assets if
we store dependencies in the processed meta file and load them ahead of
time)
### Eager ProcessorDev Asset Loading
I made a controversial call in the interest of fast startup times ("time
to first pixel") for the "processor dev mode configuration". When
initializing the AssetProcessor, current processed versions of unchanged
assets are yielded immediately, even if their dependencies haven't been
checked yet for reprocessing. This means that
non-current-state-of-filesystem-but-previously-valid assets might be
returned to the App first, then hot-reloaded if/when their dependencies
change and the asset is reprocessed.
Is this behavior desirable? There is largely one alternative: do not
yield an asset from the processor to the app until all of its
dependencies have been checked for changes. In some common cases (load
dependency has not changed since last run) this will increase startup
time. The main question is "by how much" and is that slower startup time
worth it in the interest of only yielding assets that are true to the
current state of the filesystem. Should this be configurable? I'm
starting to think we should only yield an asset after its (historical)
dependencies have been checked for changes + processed as necessary, but
I'm curious what you all think.
### Paths Are Currently The Only Canonical ID / Do We Want Asset UUIDs?
In this implementation AssetPaths are the only canonical asset
identifier (just like the previous Bevy Asset system and Godot). Moving
assets will result in re-scans (and currently reprocessing, although
reprocessing can easily be avoided with some changes). Asset
renames/moves will break code and assets that rely on specific paths,
unless those paths are fixed up.
Do we want / need "stable asset uuids"? Introducing them is very
possible:
1. Generate a UUID and include it in .meta files
2. Support UUID in AssetPath
3. Generate "asset indices" which are loaded on startup and map UUIDs to
paths.
4 (maybe). Consider only supporting UUIDs for processed assets so we can
generate quick-to-load indices instead of scanning meta files.
The main "pro" is that assets referencing UUIDs don't need to be
migrated when a path changes. The main "con" is that UUIDs cannot be
"lazily resolved" like paths. They need a full view of all assets to
answer the question "does this UUID exist". Which means UUIDs require
the AssetProcessor to fully finish startup scans before saying an asset
doesnt exist. And they essentially require asset pre-processing to use
in apps, because scanning all asset metadata files at runtime to resolve
a UUID is not viable for medium-to-large apps. It really requires a
pre-generated UUID index, which must be loaded before querying for
assets.
I personally think this should be investigated in a separate PR. Paths
aren't going anywhere ... _everyone_ uses filesystems (and
filesystem-like apis) to manage their asset source files. I consider
them permanent canonical asset information. Additionally, they behave
well for both processed and unprocessed asset modes. Given that Bevy is
supporting both, this feels like the right canonical ID to start with.
UUIDS (and maybe even other indexed-identifier types) can be added later
as necessary.
### Folder / File Naming Conventions
All asset processing config currently lives in the `.imported_assets`
folder. The processor transaction log is in `.imported_assets/log`.
Processed assets are added to `.imported_assets/Default`, which will
make migrating to processed asset profiles (ex: a
`.imported_assets/Mobile` profile) a non-breaking change. It also allows
us to create top-level files like `.imported_assets/log` without it
being interpreted as an asset. Meta files currently have a `.meta`
suffix. Do we like these names and conventions?
### Should the `AssetPlugin::processed_dev` configuration enable
`watch_for_changes` automatically?
Currently it does (which I think makes sense), but it does make it the
only configuration that enables watch_for_changes by default.
### Discuss on_loaded High Level Interface:
This PR includes a very rough "proof of concept" `on_loaded` system
adapter that uses the `LoadedWithDependencies` event in combination with
`asset_server.load_asset` dependency tracking to support this pattern
```rust
fn main() {
App::new()
.init_asset::<MyAssets>()
.add_systems(Update, on_loaded(create_array_texture))
.run();
}
#[derive(Asset, Clone)]
struct MyAssets {
#[dependency]
picture_of_my_cat: Handle<Image>,
#[dependency]
picture_of_my_other_cat: Handle<Image>,
}
impl FromWorld for ArrayTexture {
fn from_world(world: &mut World) -> Self {
picture_of_my_cat: server.load("meow.png"),
picture_of_my_other_cat: server.load("meeeeeeeow.png"),
}
}
fn spawn_cat(In(my_assets): In<MyAssets>, mut commands: Commands) {
commands.spawn(SpriteBundle {
texture: my_assets.picture_of_my_cat.clone(),
..default()
});
commands.spawn(SpriteBundle {
texture: my_assets.picture_of_my_other_cat.clone(),
..default()
});
}
```
The implementation is _very_ rough. And it is currently unsafe because
`bevy_ecs` doesn't expose some internals to do this safely from inside
`bevy_asset`. There are plenty of unanswered questions like:
* "do we add a Loadable" derive? (effectively automate the FromWorld
implementation above)
* Should `MyAssets` even be an Asset? (largely implemented this way
because it elegantly builds on `server.load_asset(MyAsset { .. })`
dependency tracking).
We should think hard about what our ideal API looks like (and if this is
a pattern we want to support). Not necessarily something we need to
solve in this PR. The current `on_loaded` impl should probably be
removed from this PR before merging.
## Clarifying Questions
### What about Assets as Entities?
This Bevy Asset V2 proposal implementation initially stored Assets as
ECS Entities. Instead of `AssetId<T>` + the `Assets<T>` resource it used
`Entity` as the asset id and Asset values were just ECS components.
There are plenty of compelling reasons to do this:
1. Easier to inline assets in Bevy Scenes (as they are "just" normal
entities + components)
2. More flexible queries: use the power of the ECS to filter assets (ex:
`Query<Mesh, With<Tree>>`).
3. Extensible. Users can add arbitrary component data to assets.
4. Things like "component visualization tools" work out of the box to
visualize asset data.
However Assets as Entities has a ton of caveats right now:
* We need to be able to allocate entity ids without a direct World
reference (aka rework id allocator in Entities ... i worked around this
in my prototypes by just pre allocating big chunks of entities)
* We want asset change events in addition to ECS change tracking ... how
do we populate them when mutations can come from anywhere? Do we use
Changed queries? This would require iterating over the change data for
all assets every frame. Is this acceptable or should we implement a new
"event based" component change detection option?
* Reconciling manually created assets with asset-system managed assets
has some nuance (ex: are they "loaded" / do they also have that
component metadata?)
* "how do we handle "static" / default entity handles" (ties in to the
Entity Indices discussion:
https://github.com/bevyengine/bevy/discussions/8319). This is necessary
for things like "built in" assets and default handles in things like
SpriteBundle.
* Storing asset information as a component makes it easy to "invalidate"
asset state by removing the component (or forcing modifications).
Ideally we have ways to lock this down (some combination of Rust type
privacy and ECS validation)
In practice, how we store and identify assets is a reasonably
superficial change (porting off of Assets as Entities and implementing
dedicated storage + ids took less than a day). So once we sort out the
remaining challenges the flip should be straightforward. Additionally, I
do still have "Assets as Entities" in my commit history, so we can reuse
that work. I personally think "assets as entities" is a good endgame,
but it also doesn't provide _significant_ value at the moment and it
certainly isn't ready yet with the current state of things.
### Why not Distill?
[Distill](https://github.com/amethyst/distill) is a high quality fully
featured asset system built in Rust. It is very natural to ask "why not
just use Distill?".
It is also worth calling out that for awhile, [we planned on adopting
Distill / I signed off on
it](https://github.com/bevyengine/bevy/issues/708).
However I think Bevy has a number of constraints that make Distill
adoption suboptimal:
* **Architectural Simplicity:**
* Distill's processor requires an in-memory database (lmdb) and RPC
networked API (using Cap'n Proto). Each of these introduces API
complexity that increases maintenance burden and "code grokability".
Ignoring tests, documentation, and examples, Distill has 24,237 lines of
Rust code (including generated code for RPC + database interactions). If
you ignore generated code, it has 11,499 lines.
* Bevy builds the AssetProcessor and AssetServer using pluggable
AssetReader/AssetWriter Rust traits with simple io interfaces. They do
not necessitate databases or RPC interfaces (although Readers/Writers
could use them if that is desired). Bevy Asset V2 (at the time of
writing this PR) is 5,384 lines of Rust code (ignoring tests,
documentation, and examples). Grain of salt: Distill does have more
features currently (ex: Asset Packing, GUIDS, remote-out-of-process
asset processor). I do plan to implement these features in Bevy Asset V2
and I personally highly doubt they will meaningfully close the 6115
lines-of-code gap.
* This complexity gap (which while illustrated by lines of code, is much
bigger than just that) is noteworthy to me. Bevy should be hackable and
there are pillars of Distill that are very hard to understand and
extend. This is a matter of opinion (and Bevy Asset V2 also has
complicated areas), but I think Bevy Asset V2 is much more approachable
for the average developer.
* Necessary disclaimer: counting lines of code is an extremely rough
complexity metric. Read the code and form your own opinions.
* **Optional Asset Processing:** Not all Bevy Apps (or Bevy App
developers) need / want asset preprocessing. Processing increases the
complexity of the development environment by introducing things like
meta files, imported asset storage, running processors in the
background, waiting for processing to finish, etc. Distill _requires_
preprocessing to work. With Bevy Asset V2 processing is fully opt-in.
The AssetServer isn't directly aware of asset processors at all.
AssetLoaders only care about converting bytes to runtime Assets ... they
don't know or care if the bytes were pre-processed or not. Processing is
"elegantly" (forgive my self-congratulatory phrasing) layered on top and
builds on the existing Asset system primitives.
* **Direct Filesystem Access to Processed Asset State:** Distill stores
processed assets in a database. This makes debugging / inspecting the
processed outputs harder (either requires special tooling to query the
database or they need to be "deployed" to be inspected). Bevy Asset V2,
on the other hand, stores processed assets in the filesystem (by default
... this is configurable). This makes interacting with the processed
state more natural. Note that both Godot and Unity's new asset system
store processed assets in the filesystem.
* **Portability**: Because Distill's processor uses lmdb and RPC
networking, it cannot be run on certain platforms (ex: lmdb is a
non-rust dependency that cannot run on the web, some platforms don't
support running network servers). Bevy should be able to process assets
everywhere (ex: run the Bevy Editor on the web, compile + process
shaders on mobile, etc). Distill does partially mitigate this problem by
supporting "streaming" assets via the RPC protocol, but this is not a
full solve from my perspective. And Bevy Asset V2 can (in theory) also
stream assets (without requiring RPC, although this isn't implemented
yet)
Note that I _do_ still think Distill would be a solid asset system for
Bevy. But I think the approach in this PR is a better solve for Bevy's
specific "asset system requirements".
### Doesn't async-fs just shim requests to "sync" `std::fs`? What is the
point?
"True async file io" has limited / spotty platform support. async-fs
(and the rust async ecosystem generally ... ex Tokio) currently use
async wrappers over std::fs that offload blocking requests to separate
threads. This may feel unsatisfying, but it _does_ still provide value
because it prevents our task pools from blocking on file system
operations (which would prevent progress when there are many tasks to
do, but all threads in a pool are currently blocking on file system
ops).
Additionally, using async APIs for our AssetReaders and AssetWriters
also provides value because we can later add support for "true async
file io" for platforms that support it. _And_ we can implement other
"true async io" asset backends (such as networked asset io).
## Draft TODO
- [x] Fill in missing filesystem event APIs: file removed event (which
is expressed as dangling RenameFrom events in some cases), file/folder
renamed event
- [x] Assets without loaders are not moved to the processed folder. This
breaks things like referenced `.bin` files for GLTFs. This should be
configurable per-non-asset-type.
- [x] Initial implementation of Reflect and FromReflect for Handle. The
"deserialization" parity bar is low here as this only worked with static
UUIDs in the old impl ... this is a non-trivial problem. Either we add a
Handle::AssetPath variant that gets "upgraded" to a strong handle on
scene load or we use a separate AssetRef type for Bevy scenes (which is
converted to a runtime Handle on load). This deserves its own discussion
in a different pr.
- [x] Populate read_asset_bytes hash when run by the processor (a bit of
a special case .. when run by the processor the processed meta will
contain the hash so we don't need to compute it on the spot, but we
don't want/need to read the meta when run by the main AssetServer)
- [x] Delay hot reloading: currently filesystem events are handled
immediately, which creates timing issues in some cases. For example hot
reloading images can sometimes break because the image isn't finished
writing. We should add a delay, likely similar to the [implementation in
this PR](https://github.com/bevyengine/bevy/pull/8503).
- [x] Port old platform-specific AssetIo implementations to the new
AssetReader interface (currently missing Android and web)
- [x] Resolve on_loaded unsafety (either by removing the API entirely or
removing the unsafe)
- [x] Runtime loader setting overrides
- [x] Remove remaining unwraps that should be error-handled. There are
number of TODOs here
- [x] Pretty AssetPath Display impl
- [x] Document more APIs
- [x] Resolve spurious "reloading because it has changed" events (to
repro run load_gltf with `processed_dev()`)
- [x] load_dependency hot reloading currently only works for processed
assets. If processing is disabled, load_dependency changes are not hot
reloaded.
- [x] Replace AssetInfo dependency load/fail counters with
`loading_dependencies: HashSet<UntypedAssetId>` to prevent reloads from
(potentially) breaking counters. Storing this will also enable
"dependency reloaded" events (see [Next Steps](#next-steps))
- [x] Re-add filesystem watcher cargo feature gate (currently it is not
optional)
- [ ] Migration Guide
- [ ] Changelog
## Followup TODO
- [ ] Replace "eager unchanged processed asset loading" behavior with
"don't returned unchanged processed asset until dependencies have been
checked".
- [ ] Add true `Ignore` AssetAction that does not copy the asset to the
imported_assets folder.
- [ ] Finish "live asset unloading" (ex: free up CPU asset memory after
uploading an image to the GPU), rethink RenderAssets, and port renderer
features. The `Assets` collection uses `Option<T>` for asset storage to
support its removal. (1) the Option might not actually be necessary ...
might be able to just remove from the collection entirely (2) need to
finalize removal apis
- [ ] Try replacing the "channel based" asset id recycling with
something a bit more efficient (ex: we might be able to use raw atomic
ints with some cleverness)
- [ ] Consider adding UUIDs to processed assets (scoped just to helping
identify moved assets ... not exposed to load queries ... see [Next
Steps](#next-steps))
- [ ] Store "last modified" source asset and meta timestamps in
processed meta files to enable skipping expensive hashing when the file
wasn't changed
- [ ] Fix "slow loop" handle drop fix
- [ ] Migrate to TypeName
- [x] Handle "loader preregistration". See #9429
## Next Steps
* **Configurable per-type defaults for AssetMeta**: It should be
possible to add configuration like "all png image meta should default to
using nearest sampling" (currently this hard-coded per-loader/processor
Settings::default() impls). Also see the "Folder Meta" bullet point.
* **Avoid Reprocessing on Asset Renames / Moves**: See the "canonical
asset ids" discussion in [Open Questions](#open-questions) and the
relevant bullet point in [Draft TODO](#draft-todo). Even without
canonical ids, folder renames could avoid reprocessing in some cases.
* **Multiple Asset Sources**: Expand AssetPath to support "asset source
names" and support multiple AssetReaders in the asset server (ex:
`webserver://some_path/image.png` backed by an Http webserver
AssetReader). The "default" asset reader would use normal
`some_path/image.png` paths. Ideally this works in combination with
multiple AssetWatchers for hot-reloading
* **Stable Type Names**: this pr removes the TypeUuid requirement from
assets in favor of `std::any::type_name`. This makes defining assets
easier (no need to generate a new uuid / use weird proc macro syntax).
It also makes reading meta files easier (because things have "friendly
names"). We also use type names for components in scene files. If they
are good enough for components, they are good enough for assets. And
consistency across Bevy pillars is desirable. However,
`std::any::type_name` is not guaranteed to be stable (although in
practice it is). We've developed a [stable type
path](https://github.com/bevyengine/bevy/pull/7184) to resolve this,
which should be adopted when it is ready.
* **Command Line Interface**: It should be possible to run the asset
processor in a separate process from the command line. This will also
require building a network-server-backed AssetReader to communicate
between the app and the processor. We've been planning to build a "bevy
cli" for awhile. This seems like a good excuse to build it.
* **Asset Packing**: This is largely an additive feature, so it made
sense to me to punt this until we've laid the foundations in this PR.
* **Per-Platform Processed Assets**: It should be possible to generate
assets for multiple platforms by supporting multiple "processor
profiles" per asset (ex: compress with format X on PC and Y on iOS). I
think there should probably be arbitrary "profiles" (which can be
separate from actual platforms), which are then assigned to a given
platform when generating the final asset distribution for that platform.
Ex: maybe devs want a "Mobile" profile that is shared between iOS and
Android. Or a "LowEnd" profile shared between web and mobile.
* **Versioning and Migrations**: Assets, Loaders, Savers, and Processors
need to have versions to determine if their schema is valid. If an asset
/ loader version is incompatible with the current version expected at
runtime, the processor should be able to migrate them. I think we should
try using Bevy Reflect for this, as it would allow us to load the old
version as a dynamic Reflect type without actually having the old Rust
type. It would also allow us to define "patches" to migrate between
versions (Bevy Reflect devs are currently working on patching). The
`.meta` file already has its own format version. Migrating that to new
versions should also be possible.
* **Real Copy-on-write AssetPaths**: Rust's actual Cow (clone-on-write
type) currently used by AssetPath can still result in String clones that
aren't actually necessary (cloning an Owned Cow clones the contents).
Bevy's asset system requires cloning AssetPaths in a number of places,
which result in actual clones of the internal Strings. This is not
efficient. AssetPath internals should be reworked to exhibit truer
cow-like-behavior that reduces String clones to the absolute minimum.
* **Consider processor-less processing**: In theory the AssetServer
could run processors "inline" even if the background AssetProcessor is
disabled. If we decide this is actually desirable, we could add this.
But I don't think its a priority in the short or medium term.
* **Pre-emptive dependency loading**: We could encode dependencies in
processed meta files, which could then be used by the Asset Server to
kick of dependency loads as early as possible (prior to starting the
actual asset load). Is this desirable? How much time would this save in
practice?
* **Optimize Processor With UntypedAssetIds**: The processor exclusively
uses AssetPath to identify assets currently. It might be possible to
swap these out for UntypedAssetIds in some places, which are smaller /
cheaper to hash and compare.
* **One to Many Asset Processing**: An asset source file that produces
many assets currently must be processed into a single "processed" asset
source. If labeled assets can be written separately they can each have
their own configured savers _and_ they could be loaded more granularly.
Definitely worth exploring!
* **Automatically Track "Runtime-only" Asset Dependencies**: Right now,
tracking "created at runtime" asset dependencies requires adding them
via `asset_server.load_asset(StandardMaterial::default())`. I think with
some cleverness we could also do this for
`materials.add(StandardMaterial::default())`, making tracking work
"everywhere". There are challenges here relating to change detection /
ensuring the server is made aware of dependency changes. This could be
expensive in some cases.
* **"Dependency Changed" events**: Some assets have runtime artifacts
that need to be re-generated when one of their dependencies change (ex:
regenerate a material's bind group when a Texture needs to change). We
are generating the dependency graph so we can definitely produce these
events. Buuuuut generating these events will have a cost / they could be
high frequency for some assets, so we might want this to be opt-in for
specific cases.
* **Investigate Storing More Information In Handles**: Handles can now
store arbitrary information, which makes it cheaper and easier to
access. How much should we move into them? Canonical asset load states
(via atomics)? (`handle.is_loaded()` would be very cool). Should we
store the entire asset and remove the `Assets<T>` collection?
(`Arc<RwLock<Option<Image>>>`?)
* **Support processing and loading files without extensions**: This is a
pretty arbitrary restriction and could be supported with very minimal
changes.
* **Folder Meta**: It would be nice if we could define per folder
processor configuration defaults (likely in a `.meta` or `.folder_meta`
file). Things like "default to linear filtering for all Images in this
folder".
* **Replace async_broadcast with event-listener?** This might be
approximately drop-in for some uses and it feels more light weight
* **Support Running the AssetProcessor on the Web**: Most of the hard
work is done here, but there are some easy straggling TODOs (make the
transaction log an interface instead of a direct file writer so we can
write a web storage backend, implement an AssetReader/AssetWriter that
reads/writes to something like LocalStorage).
* **Consider identifying and preventing circular dependencies**: This is
especially important for "processor dependencies", as processing will
silently never finish in these cases.
* **Built-in/Inlined Asset Hot Reloading**: This PR regresses
"built-in/inlined" asset hot reloading (previously provided by the
DebugAssetServer). I'm intentionally punting this because I think it can
be cleanly implemented with "multiple asset sources" by registering a
"debug asset source" (ex: `debug://bevy_pbr/src/render/pbr.wgsl` asset
paths) in combination with an AssetWatcher for that asset source and
support for "manually loading pats with asset bytes instead of
AssetReaders". The old DebugAssetServer was quite nasty and I'd love to
avoid that hackery going forward.
* **Investigate ways to remove double-parsing meta files**: Parsing meta
files currently involves parsing once with "minimal" versions of the
meta file to extract the type name of the loader/processor config, then
parsing again to parse the "full" meta. This is suboptimal. We should be
able to define custom deserializers that (1) assume the loader/processor
type name comes first (2) dynamically looks up the loader/processor
registrations to deserialize settings in-line (similar to components in
the bevy scene format). Another alternative: deserialize as dynamic
Reflect objects and then convert.
* **More runtime loading configuration**: Support using the Handle type
as a hint to select an asset loader (instead of relying on AssetPath
extensions)
* **More high level Processor trait implementations**: For example, it
might be worth adding support for arbitrary chains of "asset transforms"
that modify an in-memory asset representation between loading and
saving. (ex: load a Mesh, run a `subdivide_mesh` transform, followed by
a `flip_normals` transform, then save the mesh to an efficient
compressed format).
* **Bevy Scene Handle Deserialization**: (see the relevant [Draft TODO
item](#draft-todo) for context)
* **Explore High Level Load Interfaces**: See [this
discussion](#discuss-on_loaded-high-level-interface) for one prototype.
* **Asset Streaming**: It would be great if we could stream Assets (ex:
stream a long video file piece by piece)
* **ID Exchanging**: In this PR Asset Handles/AssetIds are bigger than
they need to be because they have a Uuid enum variant. If we implement
an "id exchanging" system that trades Uuids for "efficient runtime ids",
we can cut down on the size of AssetIds, making them more efficient.
This has some open design questions, such as how to spawn entities with
"default" handle values (as these wouldn't have access to the exchange
api in the current system).
* **Asset Path Fixup Tooling**: Assets that inline asset paths inside
them will break when an asset moves. The asset system provides the
functionality to detect when paths break. We should build a framework
that enables formats to define "path migrations". This is especially
important for scene files. For editor-generated files, we should also
consider using UUIDs (see other bullet point) to avoid the need to
migrate in these cases.
---------
Co-authored-by: BeastLe9enD <beastle9end@outlook.de>
Co-authored-by: Mike <mike.hsu@gmail.com>
Co-authored-by: Nicola Papale <nicopap@users.noreply.github.com>
# Objective
All delimiter symbols used by the path parser are ASCII, this means we
can entirely ignore UTF8 handling. This may improve performance.
## Solution
Instead of storing the path as an `&str` + the parser offset, and
reading the path using `&self.path[self.offset..]`, we store the parser
state in a `&[u8]`. This allows two optimizations:
1. Avoid UTF8 checking on `&self.path[self.offset..]`
2. Avoid any kind of bound checking, since the length of what is left to
read is stored in the `&[u8]`'s reference metadata, and is assumed valid
by the compiler.
This is a major improvement when comparing to the previous parser.
1. `access_following` and `next_token` now inline in `PathParser::next`
2. Benchmarking show a 20% performance increase (#9364)
Please note that while we ignore UTF-8 handling, **utf-8 is still
supported**. This is because we only handle "at the edges" what happens
exactly before and after a recognized `SYMBOL`. utf-8 is handled
transparently beyond that.
# 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()
# Objective
[Rust 1.72.0](https://blog.rust-lang.org/2023/08/24/Rust-1.72.0.html) is
now stable.
# Notes
- `let-else` formatting has arrived!
- I chose to allow `explicit_iter_loop` due to
https://github.com/rust-lang/rust-clippy/issues/11074.
We didn't hit any of the false positives that prevent compilation, but
fixing this did produce a lot of the "symbol soup" mentioned, e.g. `for
image in &mut *image_events {`.
Happy to undo this if there's consensus the other way.
---------
Co-authored-by: François <mockersf@gmail.com>
# Objective
Fixes#9094
## Solution
Takes a bit from
[this](https://github.com/bevyengine/bevy/issues/9094#issuecomment-1629333851)
comment as well as a
[comment](https://discord.com/channels/691052431525675048/1002362493634629796/1128024873260810271)
from @soqb.
This allows users to opt-out of the `TypePath` implementation that is
automatically generated by the `Reflect` derive macro, allowing custom
`TypePath` implementations.
```rust
#[derive(Reflect)]
#[reflect(type_path = false)]
struct Foo<T> {
#[reflect(ignore)]
_marker: PhantomData<T>,
}
struct NotTypePath;
impl<T: 'static> TypePath for Foo<T> {
fn type_path() -> &'static str {
std::any::type_name::<Self>()
}
fn short_type_path() -> &'static str {
static CELL: GenericTypePathCell = GenericTypePathCell::new();
CELL.get_or_insert::<Self, _>(|| {
bevy_utils::get_short_name(std::any::type_name::<Self>())
})
}
fn crate_name() -> Option<&'static str> {
Some("my_crate")
}
fn module_path() -> Option<&'static str> {
Some("my_crate::foo")
}
fn type_ident() -> Option<&'static str> {
Some("Foo")
}
}
// Can use `TypePath`
let _ = <Foo<NotTypePath> as TypePath>::type_path();
// Can register the type
let mut registry = TypeRegistry::default();
registry.register::<Foo<NotTypePath>>();
```
#### Type Path Stability
The stability of type paths mainly come into play during serialization.
If a type is moved between builds, an unstable type path may become
invalid.
Users that opt-out of `TypePath` and rely on something like
`std::any::type_name` as in the example above, should be aware that this
solution removes the stability guarantees. Deserialization thus expects
that type to never move. If it does, then the serialized type paths will
need to be updated accordingly.
If a user depends on stability, they will need to implement that
stability logic manually (probably by looking at the expanded output of
a typical `Reflect`/`TypePath` derive). This could be difficult for type
parameters that don't/can't implement `TypePath`, and will need to make
heavy use of string parsing and manipulation to achieve the same effect
(alternatively, they can choose to simply exclude any type parameter
that doesn't implement `TypePath`).
---
## Changelog
- Added the `#[reflect(type_path = false)]` attribute to opt out of the
`TypePath` impl when deriving `Reflect`
---------
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
It seems the behavior of field attributes was accidentally broken at
some point. Take the following code:
```rust
#[derive(Reflect)]
struct Foo {
#[reflect(ignore, default)]
value: usize
}
```
The above code should simply mark `value` as ignored and specify a
default behavior. However, what this actually does is discard both.
That's especially a problem when we don't want the field to be be given
a `Reflect` or `FromReflect` bound (which is why we ignore it in the
first place).
This only happens when the attributes are combined into one. The
following code works properly:
```rust
#[derive(Reflect)]
struct Foo {
#[reflect(ignore)]
#[reflect(default)]
value: usize
}
```
## Solution
Cleaned up the field attribute parsing logic to support combined field
attributes.
---
## Changelog
- Fixed a bug where `Reflect` derive attributes on fields are not able
to be combined into a single attribute
# Objective
- Follow up to #8887
- The parsing code in `bevy_reflect/src/path/mod.rs` could also do with
some cleanup
## Solution
- Create the `parse.rs` module, move all parsing code to this module
- The parsing errors also now keep track of the whole parsed string, and
are much more fine-grained
### Detailed changes
- Move `PathParser` to `parse.rs` submodule
- Rename `token_to_access` to `access_following` (yep, goes from 132
lines to 16)
- Move parsing tests into the `parse.rs` file
# Objective
Glam 0.24 added new glam types (```I64Vec``` and ```U64Vec```). However
these are not reflectable unlike the other glam types
## Solution
Implement reflect for these new types
---
## Changelog
Implements reflect with the impl_reflect_struct macro on ```I64Vec2```,
```I64Vec3```, ```I64Vec4```, ```U64Vec2```, ```U64Vec3```, and
```U64Vec4``` types
# Objective
- The `path` module was getting fairly large.
- The code in `AccessRef::read_element` and mut equivalent was very
complex and difficult to understand.
- The `ReflectPathError` had a lot of variants, and was difficult to
read.
## Solution
- Split the file in two, `access` now has its own module
- Rewrite the `read_element` methods, they were ~200 lines long, they
are now ~70 lines long — I didn't change any of the logic. It's really
just the same code, but error handling is separated.
- Split the `ReflectPathError` error
- Merge `AccessRef` and `Access`
- A few other changes that aim to reduce code complexity
### Fully detailed change list
- `Display` impl of `ParsedPath` now includes prefix dots — this allows
simplifying its implementation, and IMO `.path.to.field` is a better way
to express a "path" than `path.to.field` which could suggest we are
reading the `to` field of a variable named `path`
- Add a test to check that dot prefixes and other are correctly parsed —
Until now, no test contained a prefixing dot
- Merge `Access` and `AccessRef`, using a `Cow<'a, str>`. Generated code
seems to agree with this decision (`ParsedPath::parse` sheds 5% of
instructions)
- Remove `Access::as_ref` since there is no such thing as an `AccessRef`
anymore.
- Rename `AccessRef::to_owned` into `AccessRef::into_owned()` since it
takes ownership of `self` now.
- Add a `parse_static` that doesn't allocate new strings for named
fields!
- Add a section about path reflection in the `bevy_reflect` crate root
doc — I saw a few people that weren't aware of path reflection, so I
thought it was pertinent to add it to the root doc
- a lot of nits
- rename `index` to `offset` when it refers to offset in the path string
— There is no more confusion with the other kind of indices in this
context, also it's a common naming convention for parsing.
- Make a dedicated enum for parsing errors
- rename the `read_element` methods to `element` — shorter, but also
`read_element_mut` was a fairly poor name
- The error values now not only contain the expected type but also the
actual type.
- Remove lifetimes that could be inferred from the `GetPath` trait
methods.
---
## Change log
- Added the `ParsedPath::parse_static` method, avoids allocating when
parsing `&'static str`.
## Migration Guide
If you were matching on the `Err(ReflectPathError)` value returned by
`GetPath` and `ParsedPath` methods, now only the parse-related errors
and the offset are publicly accessible. You can always use the
`fmt::Display` to get a clear error message, but if you need
programmatic access to the error types, please open an issue.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Gino Valente <49806985+MrGVSV@users.noreply.github.com>
