Commit graph

72 commits

Author SHA1 Message Date
John Lewis
cfe4034d25
Add Reflection for Wrapping/Saturating types (#11397)
# 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`.
2024-01-22 15:21:20 +00:00
BD103
056b006d4e
Use static_assertions to check for trait impls (#11407)
# 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?
2024-01-18 17:21:18 +00:00
Adam
fe68005f71
Implement TypePath for EntityHash (#11195)
# 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.
2024-01-04 18:28:31 +00:00
Mike
786abbf3f5
Fix ci xvfb (#11143)
# 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>
2023-12-30 09:07:31 +00:00
Tygyh
1568d4a415
Reorder impl to be the same as the trait (#11076)
# Objective

- Make the implementation order consistent between all sources to fit
the order in the trait.

## Solution

- Change the implementation order.
2023-12-24 17:43:55 +00:00
tygyh
fd308571c4
Remove unnecessary path prefixes (#10749)
# 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.
2023-11-28 23:43:40 +00:00
radiish
262846e702
reflect: TypePath part 2 (#8768)
# 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.
2023-10-09 19:33:03 +00:00
Carter Anderson
5eb292dc10
Bevy Asset V2 (#8624)
# 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>
2023-09-07 02:07:27 +00:00
ClayenKitten
ffc572728f
Fix typos throughout the project (#9090)
# Objective

Fix typos throughout the project.

## Solution

[`typos`](https://github.com/crate-ci/typos) project was used for
scanning, but no automatic corrections were applied. I checked
everything by hand before fixing.

Most of the changes are documentation/comments corrections. Also, there
are few trivial changes to code (variable name, pub(crate) function name
and a few error/panic messages).

## Unsolved

`bevy_reflect_derive` has
[typo](1b51053f19/crates/bevy_reflect/bevy_reflect_derive/src/type_path.rs (L76))
in enum variant name that I didn't fix. Enum is `pub(crate)`, so there
shouldn't be any trouble if fixed. However, code is tightly coupled with
macro usage, so I decided to leave it for more experienced contributor
just in case.
2023-07-10 00:11:51 +00:00
Gino Valente
aeeb20ec4c
bevy_reflect: FromReflect Ergonomics Implementation (#6056)
# Objective

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

---

Resolves #4597

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

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

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

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

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

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

## Solution

Automatically derive `FromReflect` when deriving `Reflect`.

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

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

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

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

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

#### `ReflectFromReflect`

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

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

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

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

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

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

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

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

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

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

</details>

---

## Changelog

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

## Migration Guide

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

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

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

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

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

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

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

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

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

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

</details>

---------

Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2023-06-29 01:31:34 +00:00
EliasPrescott
e6b655fb25
adding reflection for Cow<'static, [T]> (#7454)
# Objective

- Implementing reflection for Cow<'static, [T]>
- Hopefully fixes #7429

## Solution

- Implementing Reflect, Typed, GetTypeRegistration, and FromReflect for
Cow<'static, [T]>

---

## Notes

I have not used bevy_reflection much yet, so I may not fully understand
all the use cases. This is also my first attempt at contributing, so I
would appreciate any feedback or recommendations for changes. I tried to
add cases for using Cow<'static, str> and Cow<'static, [u8]> to some of
the bevy_reflect tests, but I can't guarantee those tests are
comprehensive enough.

---------

Co-authored-by: MinerSebas <66798382+MinerSebas@users.noreply.github.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2023-06-19 14:58:49 +00:00
Carter Anderson
8b9d88f4d0
Reflect now requires DynamicTypePath. Remove Reflect::get_type_path() (#8764)
Followup to #7184

This makes `Reflect: DynamicTypePath` which allows us to remove
`Reflect::get_type_path`, reducing unnecessary codegen and simplifying
`Reflect` implementations.
2023-06-06 17:23:58 +00:00
radiish
1efc762924
reflect: stable type path v2 (#7184)
# Objective

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


## Solution

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

---

## Changelog

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

## Migration Guide

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

## Open Questions
- [x] ~This PR currently does not migrate any usages of
`std::any::type_name` to use `bevy_reflect::TypePath` to ease the review
process. Should it?~ Migration will be left to a follow-up PR.
- [ ] This PR adds a lot of `#[derive(TypePath)]` and `T: TypePath` to
satisfy new bounds, mostly when deriving `TypeUuid`. Should we make
`TypePath` a supertrait of `TypeUuid`? [Should we remove `TypeUuid` in
favour of
`TypePath`?](2afbd85532 (r961067892))
2023-06-05 20:31:20 +00:00
Егор Куклин
6b4c7d5d88
Add get_at_mut to bevy_reflect::Map trait (#8691)
# Objective

Fixes #8596 

## Solution

Change interface of the trait Map. Adjust implementations of this trait

---

## Changelog

### Changed
- Interface of Map trait

### Added
- `Map::get_at_mut`

## Migration Guide

Every implementor of Map trait would need to implement `get_at_mut`.
Which, judging by changes in this PR, should be fairly trivial.
2023-06-02 12:24:40 +00:00
Gauthier Acquitter
acf1362b9a
bevy_reflect: Allow construction of MapIter outside of the bevy_reflect crate. (#8723)
# Objective

Right now it's impossible to construct a MapIter outside of the
bevy_reflect crate, making it impossible to implement the Map trait for
custom map types.

## Solution

Addition of a pub constructor to MapIter.
2023-06-01 10:12:57 +00:00
Mincho Paskalev
fe57b9f744
Add Reflect and FromReflect for AssetPath (#8531)
# Objective

- Add Reflect and FromReflect for AssetPath
- Fixes #8458

## Solution

- Straightforward derive of `Reflect` and `FromReflect` for `AssetPath`
- Implement `Reflect` and `FromReflect` for `Cow<'static, Path>` as to
satisfy the 'static lifetime requierments of bevy_reflect.
Implementation is a direct copy of that for `Cow<'static, str>` so maybe
it begs the question that was already asked in #7429 - maybe it would be
benefitial to write a general implementation for `Reflect` for
`Cow<'static, T>`.
2023-05-08 19:19:19 +00:00
Gino Valente
75130bd5ec
bevy_reflect: Better proxies (#6971)
# Objective

> This PR is based on discussion from #6601

The Dynamic types (e.g. `DynamicStruct`, `DynamicList`, etc.) act as
both:
1. Dynamic containers which may hold any arbitrary data
2. Proxy types which may represent any other type

Currently, the only way we can represent the proxy-ness of a Dynamic is
by giving it a name.

```rust
// This is just a dynamic container
let mut data = DynamicStruct::default();

// This is a "proxy"
data.set_name(std::any::type_name::<Foo>());
```

This type name is the only way we check that the given Dynamic is a
proxy of some other type. When we need to "assert the type" of a `dyn
Reflect`, we call `Reflect::type_name` on it. However, because we're
only using a string to denote the type, we run into a few gotchas and
limitations.

For example, hashing a Dynamic proxy may work differently than the type
it proxies:

```rust
#[derive(Reflect, Hash)]
#[reflect(Hash)]
struct Foo(i32);

let concrete = Foo(123);
let dynamic = concrete.clone_dynamic();

let concrete_hash = concrete.reflect_hash();
let dynamic_hash = dynamic.reflect_hash();

// The hashes are not equal because `concrete` uses its own `Hash` impl
// while `dynamic` uses a reflection-based hashing algorithm
assert_ne!(concrete_hash, dynamic_hash);
```

Because the Dynamic proxy only knows about the name of the type, it's
unaware of any other information about it. This means it also differs on
`Reflect::reflect_partial_eq`, and may include ignored or skipped fields
in places the concrete type wouldn't.

## Solution

Rather than having Dynamics pass along just the type name of proxied
types, we can instead have them pass around the `TypeInfo`.

Now all Dynamic types contain an `Option<&'static TypeInfo>` rather than
a `String`:

```diff
pub struct DynamicTupleStruct {
-    type_name: String,
+    represented_type: Option<&'static TypeInfo>,
    fields: Vec<Box<dyn Reflect>>,
}
```

By changing `Reflect::get_type_info` to
`Reflect::represented_type_info`, hopefully we make this behavior a
little clearer. And to account for `None` values on these dynamic types,
`Reflect::represented_type_info` now returns `Option<&'static
TypeInfo>`.

```rust
let mut data = DynamicTupleStruct::default();

// Not proxying any specific type
assert!(dyn_tuple_struct.represented_type_info().is_none());

let type_info = <Foo as Typed>::type_info();
dyn_tuple_struct.set_represented_type(Some(type_info));
// Alternatively:
// let dyn_tuple_struct = foo.clone_dynamic();

// Now we're proxying `Foo`
assert!(dyn_tuple_struct.represented_type_info().is_some());
```

This means that we can have full access to all the static type
information for the proxied type. Future work would include
transitioning more static type information (trait impls, attributes,
etc.) over to the `TypeInfo` so it can actually be utilized by Dynamic
proxies.

### Alternatives & Rationale

> **Note** 
> These alternatives were written when this PR was first made using a
`Proxy` trait. This trait has since been removed.

<details>
<summary>View</summary>

#### Alternative: The `Proxy<T>` Approach

I had considered adding something like a `Proxy<T>` type where `T` would
be the Dynamic and would contain the proxied type information.

This was nice in that it allows us to explicitly determine whether
something is a proxy or not at a type level. `Proxy<DynamicStruct>`
proxies a struct. Makes sense.

The reason I didn't go with this approach is because (1) tuples, (2)
complexity, and (3) `PartialReflect`.

The `DynamicTuple` struct allows us to represent tuples at runtime. It
also allows us to do something you normally can't with tuples: add new
fields. Because of this, adding a field immediately invalidates the
proxy (e.g. our info for `(i32, i32)` doesn't apply to `(i32, i32,
NewField)`). By going with this PR's approach, we can just remove the
type info on `DynamicTuple` when that happens. However, with the
`Proxy<T>` approach, it becomes difficult to represent this behavior—
we'd have to completely control how we access data for `T` for each `T`.

Secondly, it introduces some added complexities (aside from the manual
impls for each `T`). Does `Proxy<T>` impl `Reflect`? Likely yes, if we
want to represent it as `dyn Reflect`. What `TypeInfo` do we give it?
How would we forward reflection methods to the inner type (remember, we
don't have specialization)? How do we separate this from Dynamic types?
And finally, how do all this in a way that's both logical and intuitive
for users?

Lastly, introducing a `Proxy` trait rather than a `Proxy<T>` struct is
actually more inline with the [Unique Reflect
RFC](https://github.com/bevyengine/rfcs/pull/56). In a way, the `Proxy`
trait is really one part of the `PartialReflect` trait introduced in
that RFC (it's technically not in that RFC but it fits well with it),
where the `PartialReflect` serves as a way for proxies to work _like_
concrete types without having full access to everything a concrete
`Reflect` type can do. This would help bridge the gap between the
current state of the crate and the implementation of that RFC.

All that said, this is still a viable solution. If the community
believes this is the better path forward, then we can do that instead.
These were just my reasons for not initially going with it in this PR.

#### Alternative: The Type Registry Approach

The `Proxy` trait is great and all, but how does it solve the original
problem? Well, it doesn't— yet!

The goal would be to start moving information from the derive macro and
its attributes to the generated `TypeInfo` since these are known
statically and shouldn't change. For example, adding `ignored: bool` to
`[Un]NamedField` or a list of impls.

However, there is another way of storing this information. This is, of
course, one of the uses of the `TypeRegistry`. If we're worried about
Dynamic proxies not aligning with their concrete counterparts, we could
move more type information to the registry and require its usage.

For example, we could replace `Reflect::reflect_hash(&self)` with
`Reflect::reflect_hash(&self, registry: &TypeRegistry)`.

That's not the _worst_ thing in the world, but it is an ergonomics loss.

Additionally, other attributes may have their own requirements, further
restricting what's possible without the registry. The `Reflect::apply`
method will require the registry as well now. Why? Well because the
`map_apply` function used for the `Reflect::apply` impls on `Map` types
depends on `Map::insert_boxed`, which (at least for `DynamicMap`)
requires `Reflect::reflect_hash`. The same would apply when adding
support for reflection-based diffing, which will require
`Reflect::reflect_partial_eq`.

Again, this is a totally viable alternative. I just chose not to go with
it for the reasons above. If we want to go with it, then we can close
this PR and we can pursue this alternative instead.

#### Downsides

Just to highlight a quick potential downside (likely needs more
investigation): retrieving the `TypeInfo` requires acquiring a lock on
the `GenericTypeInfoCell` used by the `Typed` impls for generic types
(non-generic types use a `OnceBox which should be faster). I am not sure
how much of a performance hit that is and will need to run some
benchmarks to compare against.

</details>

### Open Questions

1. Should we use `Cow<'static, TypeInfo>` instead? I think that might be
easier for modding? Perhaps, in that case, we need to update
`Typed::type_info` and friends as well?
2. Are the alternatives better than the approach this PR takes? Are
there other alternatives?

---

## Changelog

### Changed

- `Reflect::get_type_info` has been renamed to
`Reflect::represented_type_info`
- This method now returns `Option<&'static TypeInfo>` rather than just
`&'static TypeInfo`

### Added

- Added `Reflect::is_dynamic` method to indicate when a type is dynamic
- Added a `set_represented_type` method on all dynamic types

### Removed

- Removed `TypeInfo::Dynamic` (use `Reflect::is_dynamic` instead)
- Removed `Typed` impls for all dynamic types

## Migration Guide

- The Dynamic types no longer take a string type name. Instead, they
require a static reference to `TypeInfo`:

    ```rust
    #[derive(Reflect)]
    struct MyTupleStruct(f32, f32);
    
    let mut dyn_tuple_struct = DynamicTupleStruct::default();
    dyn_tuple_struct.insert(1.23_f32);
    dyn_tuple_struct.insert(3.21_f32);
    
    // BEFORE:
    let type_name = std::any::type_name::<MyTupleStruct>();
    dyn_tuple_struct.set_name(type_name);
    
    // AFTER:
    let type_info = <MyTupleStruct as Typed>::type_info();
    dyn_tuple_struct.set_represented_type(Some(type_info));
    ```

- `Reflect::get_type_info` has been renamed to
`Reflect::represented_type_info` and now also returns an
`Option<&'static TypeInfo>` (instead of just `&'static TypeInfo`):

    ```rust
    // BEFORE:
    let info: &'static TypeInfo = value.get_type_info();
    // AFTER:
let info: &'static TypeInfo = value.represented_type_info().unwrap();
    ```

- `TypeInfo::Dynamic` and `DynamicInfo` has been removed. Use
`Reflect::is_dynamic` instead:
   
    ```rust
    // BEFORE:
    if matches!(value.get_type_info(), TypeInfo::Dynamic) {
      // ...
    }
    // AFTER:
    if value.is_dynamic() {
      // ...
    }
    ```

---------

Co-authored-by: radiish <cb.setho@gmail.com>
2023-04-26 12:17:46 +00:00
Noah
a9f766ceb2
Fix Box<dyn Reflect> struct with a hashmap in it panicking when clone_value is called on it (#8184)
# Objective

- Fix the issue described in #8183: Box<dyn Reflect> structs with a
hashmap in them will panic when clone_value is called on it
- Fixes: #8183

## Solution

- Updates the implementation of Reflect for Hashmaps to make clone_value
call from_reflect on the key before inserting it into the new struct
2023-04-22 02:55:53 +00:00
TheBigCheese
3d3444b981 impl Reflect for std::collections::HashMap instead of only bevy::utils::HashMap (#7739) (#7782)
# Objective

Implement `Reflect` for `std::collections::HashMap<K, V, S>` as well as `hashbrown::HashMap<K, V, S>` rather than just for `hashbrown::HashMap<K, V, RandomState>`. Fixes #7739.

## Solution

Rather than implementing on `HashMap<K, V>` I instead implemented most of the related traits on `HashMap<K, V, S> where S: BuildHasher + Send + Sync + 'static` and then `FromReflect` also needs the extra bound `S: Default` because it needs to use `with_capacity_and_hasher` so needs to be able to generate a default hasher.

As the API of `hashbrown::HashMap` is identical to `collections::HashMap` making them both work just required creating an `impl_reflect_for_hashmap` macro like the `impl_reflect_for_veclike` above and then applying this to both HashMaps.

---

## Changelog

`std::collections::HashMap` can now be reflected. Also more `State` generics than just `RandomState` can now be reflected for both `hashbrown::HashMap` and `collections::HashMap`
2023-02-27 21:37:36 +00:00
Johan Klokkhammer Helsing
18cfb226db Use a fixed state hasher in bevy_reflect for deterministic Reflect::reflect_hash() across processes (#7583)
# Objective

- bevy_ggrs uses `reflect_hash` in order to produce checksums for its world snapshots. These checksums are sent between clients in order to detect desyncronization.
- However, since we currently use `async::AHasher` with the `std` feature, this means that hashes will always be different for different peers, even if the state is identical.
- This means bevy_ggrs needs a way to get a deterministic (fixed) hash.

## Solution

- ~~Add a feature to use `bevy_utils::FixedState` for the hasher used by bevy_reflect.~~
- Always use `bevy_utils::FixedState` for initializing the bevy_reflect hasher. 

---

## Changelog

- bevy_reflect now uses a fixed state for its hasher, which means the output of `Reflect::reflect_hash` is now deterministic across processes.
2023-02-17 15:37:35 +00:00
Gino Valente
724b36289c bevy_reflect: Decouple List and Array traits (#7467)
# Objective

Resolves #7121

## Solution

Decouples `List` and `Array` by removing `Array` as a supertrait of `List`. Additionally, similar methods from `Array` have been added to `List` so that their usages can remain largely unchanged.

#### Possible Alternatives

##### `Sequence`

My guess for why we originally made `List` a subtrait of `Array` is that they share a lot of common operations. We could potentially move these overlapping methods to a `Sequence` (name taken from #7059) trait and make that a supertrait of both. This would allow functions to contain logic that simply operates on a sequence rather than "list vs array".

However, this means that we'd need to add methods for converting to a `dyn Sequence`. It also might be confusing since we wouldn't add a `ReflectRef::Sequence` or anything like that. Is such a trait worth adding (either in this PR or a followup one)? 

---

## Changelog

- Removed `Array` as supertrait of `List`
  - Added methods to `List` that were previously provided by `Array`

## Migration Guide

The `List` trait is no longer dependent on `Array`. Implementors of `List` can remove the `Array` impl and move its methods into the `List` impl (with only a couple tweaks).

```rust
// BEFORE
impl Array for Foo {
  fn get(&self, index: usize) -> Option<&dyn Reflect> {/* ... */}
  fn get_mut(&mut self, index: usize) -> Option<&mut dyn Reflect> {/* ... */}
  fn len(&self) -> usize {/* ... */}
  fn is_empty(&self) -> bool {/* ... */}
  fn iter(&self) -> ArrayIter {/* ... */}
  fn drain(self: Box<Self>) -> Vec<Box<dyn Reflect>> {/* ... */}
  fn clone_dynamic(&self) -> DynamicArray {/* ... */}
}

impl List for Foo {
  fn insert(&mut self, index: usize, element: Box<dyn Reflect>) {/* ... */}
  fn remove(&mut self, index: usize) -> Box<dyn Reflect> {/* ... */}
  fn push(&mut self, value: Box<dyn Reflect>) {/* ... */}
  fn pop(&mut self) -> Option<Box<dyn Reflect>> {/* ... */}
  fn clone_dynamic(&self) -> DynamicList {/* ... */}
}

// AFTER
impl List for Foo {
  fn get(&self, index: usize) -> Option<&dyn Reflect> {/* ... */}
  fn get_mut(&mut self, index: usize) -> Option<&mut dyn Reflect> {/* ... */}
  fn insert(&mut self, index: usize, element: Box<dyn Reflect>) {/* ... */}
  fn remove(&mut self, index: usize) -> Box<dyn Reflect> {/* ... */}
  fn push(&mut self, value: Box<dyn Reflect>) {/* ... */}
  fn pop(&mut self) -> Option<Box<dyn Reflect>> {/* ... */}
  fn len(&self) -> usize {/* ... */}
  fn is_empty(&self) -> bool {/* ... */}
  fn iter(&self) -> ListIter {/* ... */}
  fn drain(self: Box<Self>) -> Vec<Box<dyn Reflect>> {/* ... */}
  fn clone_dynamic(&self) -> DynamicList {/* ... */}
}
```

Some other small tweaks that will need to be made include:
- Use `ListIter` for `List::iter` instead of `ArrayIter` (the return type from `Array::iter`)
- Replace `array_hash` with `list_hash` in `Reflect::reflect_hash` for implementors of `List`
2023-02-13 21:07:53 +00:00
CrystaLamb
4fd092fbec fix typo in bevy_reflect::impls::std GetTypeRegistration for vec like… (#7520)
Implementing GetTypeRegistration in macro impl_reflect_for_veclike! had typos!
It only implement GetTypeRegistration for Vec<T>, but not for VecDeque<T>.
This will cause serialization and deserialization failure.
2023-02-06 12:58:21 +00:00
Elbert Ronnie
615d3d2157 Add constructor new to ArrayIter (#7449)
# Objective

- Fixes #7430.

## Solution

- Changed fields of `ArrayIter` to be private.
- Add a constructor `new` to `ArrayIter`.
- Replace normal struct creation with `new`.

---

## Changelog

- Add a constructor `new` to `ArrayIter`.


Co-authored-by: Elbert Ronnie <103196773+elbertronnie@users.noreply.github.com>
2023-01-31 23:19:19 +00:00
Gino Valente
229d6c686f bevy_reflect: Simplify take-or-else-from_reflect operation (#6566)
# Objective

There are times where we want to simply take an owned `dyn Reflect` and cast it to a type `T`.

Currently, this involves doing:

```rust
let value = value.take::<T>().unwrap_or_else(|value| {
  T::from_reflect(&*value).unwrap_or_else(|| {
    panic!(
      "expected value of type {} to convert to type {}.",
      value.type_name(),
      std::any::type_name::<T>()
    )
  })
});
```

This is a common operation that could be easily be simplified.

## Solution

Add the `FromReflect::take_from_reflect` method. This first tries to `take` the value, calling `from_reflect` iff that fails.

```rust
let value = T::take_from_reflect(value).unwrap_or_else(|value| {
  panic!(
    "expected value of type {} to convert to type {}.",
    value.type_name(),
    std::any::type_name::<T>()
  )
});
```

Based on suggestion from @soqb on [Discord](https://discord.com/channels/691052431525675048/1002362493634629796/1041046880316043374).

---

## Changelog

- Add `FromReflect::take_from_reflect` method
2023-01-11 16:25:37 +00:00
radiish
1b9c156479 reflect: add insert and remove methods to List (#7063)
# Objective

- Fixes #7061

## Solution

- Add and implement `insert` and `remove` methods for `List`.

---

## Changelog

- Added `insert` and `remove` methods to `List`.
- Changed the `push` and `pop` methods on `List` to have default implementations.

## Migration Guide

- Manual implementors of `List` need to implement the new methods `insert` and `remove` and 
consider whether to use the new default implementation of `push` and `pop`.

Co-authored-by: radiish <thesethskigamer@gmail.com>
2023-01-09 19:47:07 +00:00
James Liu
b37a6ca9a2 Add reflection support for VecDeque (#6831)
# Objective
This is an adoption of #5792. Fixes #5791.

## Solution
Implemented all the required reflection traits for `VecDeque`, taking from `Vec`'s impls.

---

## Changelog
Added: `std::collections::VecDeque` now implements `Reflect` and all relevant traits.

Co-authored-by: james7132 <contact@jamessliu.com>
2022-12-11 18:22:08 +00:00
Gino Valente
6ada3566ac bevy_reflect: Fix misplaced impls (#6829)
# Objective

> Followup to [this](https://github.com/bevyengine/bevy/pull/6755#discussion_r1032671178) comment

Rearrange the impls in the `impls/std.rs` file.

The issue was that I had accidentally misplaced the impl for `Option<T>` and put it between the `Cow<'static, str>` impls. This is just a slight annoyance and readability issue.

## Solution

Move the `Option<T>` and `&'static Path` impls around to be more readable.
2022-12-03 03:35:45 +00:00
Hennadii Chernyshchyk
523072902c Fix reflection for PathBuf and OsString (#6776)
# Objective

- `PathBuf` and `OsString` not reflected correctly.

## Solution

- Add missing registrations.
- Add FromReflect impls.
- Always implement `Reflect` for `OsString` just skip `Serialize` and `Deserialize` for unsupported platforms.

---

## Changelog

## Fixed

- Fix reflection for `PathBuf` and `OsString`.
2022-11-27 17:28:06 +00:00
JoJoJet
03bde74766 impl Reflect for &'static Path (#6755)
# Objective

Fixes #6739 

## Solution

Implement the required traits. They cannot be implemented for `Path` directly, since it is a dynamically-sized type.
2022-11-25 23:49:26 +00:00
radiish
9498bfffcb Add remove method to Map reflection trait. (#6564)
# Objective

- Implements removal of entries from a `dyn Map`
- Fixes #6563

## Solution

- Adds a `remove` method to the `Map` trait which takes in a `&dyn Reflect` key and returns the value removed if it was present.

---

## Changelog

- Added `Map::remove`

## Migration Guide

- Implementors of `Map` will need to implement the `remove` method.


Co-authored-by: radiish <thesethskigamer@gmail.com>
2022-11-14 21:03:39 +00:00
Gino Valente
02fbf16c80 bevy_reflect: Add Reflect::into_reflect (#6502)
# Objective

Using `Reflect` we can easily switch between a specific reflection trait object, such as a `dyn Struct`, to a `dyn Reflect` object via `Reflect::as_reflect` or `Reflect::as_reflect_mut`.

```rust
fn do_something(value: &dyn Reflect) {/* ... */}

let foo: Box<dyn Struct> = Box::new(Foo::default());
do_something(foo.as_reflect());
```

However, there is no way to convert a _boxed_ reflection trait object to a `Box<dyn Reflect>`.

## Solution

Add a `Reflect::into_reflect` method which allows converting a boxed reflection trait object back into a boxed `Reflect` trait object.

```rust
fn do_something(value: Box<dyn Reflect>) {/* ... */}

let foo: Box<dyn Struct> = Box::new(Foo::default());
do_something(foo.into_reflect());
```

---

## Changelog

- Added `Reflect::into_reflect`
2022-11-07 02:11:16 +00:00
Hennadii Chernyshchyk
feebbc5ea9 Add reflect_owned (#6494)
# Objective

There is no way to gen an owned value of `Reflect`.

## Solution

Add it! This was originally a part of #6421, but @MrGVSV asked me to create a separate for it to implement reflect diffing.

---

## Changelog

### Added

- `Reflect::reflect_owned` to get an owned version of `Reflect`.
2022-11-06 16:58:38 +00:00
Jakob Hellermann
55b3cb0183 add ReflectDefault to std types (#6429)
# Objective

- `ReflectDefault` can be used to create default values for reflected types
- `std` primitives that are `Default`-constructable should register `ReflectDefault`

## Solution

- register `ReflectDefault`
2022-10-31 16:35:22 +00:00
Hennadii Chernyshchyk
ca3e6e6797 Impl Reflect for PathBuf and OsString (#6193)
# Objective

`Reflect` impl is missing for `PathBuf` and `OsString`. Closes #6166.

## Solution

Add implementations.

---

## Changelog

### Added

`Reflect` impls for `PathBuf` and `OsString`.
2022-10-08 17:02:21 +00:00
Gino Valente
d30d3e752a bevy_reflect: Improve serialization format even more (#5723)
> Note: This is rebased off #4561 and can be viewed as a competitor to that PR. See `Comparison with #4561` section for details.

# Objective

The current serialization format used by `bevy_reflect` is both verbose and error-prone. Taking the following structs[^1] for example:

```rust
// -- src/inventory.rs

#[derive(Reflect)]
struct Inventory {
  id: String,
  max_storage: usize,
  items: Vec<Item>
}

#[derive(Reflect)]
struct Item {
  name: String
}
```

Given an inventory of a single item, this would serialize to something like:

```rust
// -- assets/inventory.ron

{
  "type": "my_game::inventory::Inventory",
  "struct": {
    "id": {
      "type": "alloc::string::String",
      "value": "inv001",
    },
    "max_storage": {
      "type": "usize",
      "value": 10
    },
    "items": {
      "type": "alloc::vec::Vec<alloc::string::String>",
      "list": [
        {
          "type": "my_game::inventory::Item",
          "struct": {
            "name": {
              "type": "alloc::string::String",
              "value": "Pickaxe"
            },
          },
        },
      ],
    },
  },
}
```

Aside from being really long and difficult to read, it also has a few "gotchas" that users need to be aware of if they want to edit the file manually. A major one is the requirement that you use the proper keys for a given type. For structs, you need `"struct"`. For lists, `"list"`. For tuple structs, `"tuple_struct"`. And so on.

It also ***requires*** that the `"type"` entry come before the actual data. Despite being a map— which in programming is almost always orderless by default— the entries need to be in a particular order. Failure to follow the ordering convention results in a failure to deserialize the data.

This makes it very prone to errors and annoyances.


## Solution

Using #4042, we can remove a lot of the boilerplate and metadata needed by this older system. Since we now have static access to type information, we can simplify our serialized data to look like:

```rust
// -- assets/inventory.ron

{
  "my_game::inventory::Inventory": (
    id: "inv001",
    max_storage: 10,
    items: [
      (
        name: "Pickaxe"
      ),
    ],
  ),
}
```

This is much more digestible and a lot less error-prone (no more key requirements and no more extra type names).

Additionally, it is a lot more familiar to users as it follows conventional serde mechanics. For example, the struct is represented with `(...)` when serialized to RON.

#### Custom Serialization

Additionally, this PR adds the opt-in ability to specify a custom serde implementation to be used rather than the one created via reflection. For example[^1]:

```rust
// -- src/inventory.rs

#[derive(Reflect, Serialize)]
#[reflect(Serialize)]
struct Item {
  #[serde(alias = "id")]
  name: String
}
```

```rust
// -- assets/inventory.ron

{
  "my_game::inventory::Inventory": (
    id: "inv001",
    max_storage: 10,
    items: [
      (
        id: "Pickaxe"
      ),
    ],
  ),
},
```

By allowing users to define their own serialization methods, we do two things:

1. We give more control over how data is serialized/deserialized to the end user
2. We avoid having to re-define serde's attributes and forcing users to apply both (e.g. we don't need a `#[reflect(alias)]` attribute).

### Improved Formats

One of the improvements this PR provides is the ability to represent data in ways that are more conventional and/or familiar to users. Many users are familiar with RON so here are some of the ways we can now represent data in RON:

###### Structs

```js
{
  "my_crate::Foo": (
    bar: 123
  )
}
// OR
{
  "my_crate::Foo": Foo(
    bar: 123
  )
}
```

<details>
<summary>Old Format</summary>

```js
{
  "type": "my_crate::Foo",
  "struct": {
    "bar": {
      "type": "usize",
      "value": 123
    }
  }
}
```

</details>

###### Tuples

```js
{
  "(f32, f32)": (1.0, 2.0)
}
```

<details>
<summary>Old Format</summary>

```js
{
  "type": "(f32, f32)",
  "tuple": [
    {
      "type": "f32",
      "value": 1.0
    },
    {
      "type": "f32",
      "value": 2.0
    }
  ]
}
```

</details>

###### Tuple Structs

```js
{
  "my_crate::Bar": ("Hello World!")
}
// OR
{
  "my_crate::Bar": Bar("Hello World!")
}
```

<details>
<summary>Old Format</summary>

```js
{
  "type": "my_crate::Bar",
  "tuple_struct": [
    {
      "type": "alloc::string::String",
      "value": "Hello World!"
    }
  ]
}
```

</details>

###### Arrays

It may be a bit surprising to some, but arrays now also use the tuple format. This is because they essentially _are_ tuples (a sequence of values with a fixed size), but only allow for homogenous types. Additionally, this is how RON handles them and is probably a result of the 32-capacity limit imposed on them (both by [serde](https://docs.rs/serde/latest/serde/trait.Serialize.html#impl-Serialize-for-%5BT%3B%2032%5D) and by [bevy_reflect](https://docs.rs/bevy/latest/bevy/reflect/trait.GetTypeRegistration.html#impl-GetTypeRegistration-for-%5BT%3B%2032%5D)).

```js
{
  "[i32; 3]": (1, 2, 3)
}
```

<details>
<summary>Old Format</summary>

```js
{
  "type": "[i32; 3]",
  "array": [
    {
      "type": "i32",
      "value": 1
    },
    {
      "type": "i32",
      "value": 2
    },
    {
      "type": "i32",
      "value": 3
    }
  ]
}
```

</details>

###### Enums

To make things simple, I'll just put a struct variant here, but the style applies to all variant types:

```js
{
  "my_crate::ItemType": Consumable(
    name: "Healing potion"
  )
}
```

<details>
<summary>Old Format</summary>

```js
{
  "type": "my_crate::ItemType",
  "enum": {
    "variant": "Consumable",
    "struct": {
      "name": {
        "type": "alloc::string::String",
        "value": "Healing potion"
      }
    }
  }
}
```

</details>

### Comparison with #4561

This PR is a rebased version of #4561. The reason for the split between the two is because this PR creates a _very_ different scene format. You may notice that the PR descriptions for either PR are pretty similar. This was done to better convey the changes depending on which (if any) gets merged first. If #4561 makes it in first, I will update this PR description accordingly.

---

## Changelog

* Re-worked serialization/deserialization for reflected types
* Added `TypedReflectDeserializer` for deserializing data with known `TypeInfo`
* Renamed `ReflectDeserializer` to `UntypedReflectDeserializer` 
* ~~Replaced usages of `deserialize_any` with `deserialize_map` for non-self-describing formats~~ Reverted this change since there are still some issues that need to be sorted out (in a separate PR). By reverting this, crates like `bincode` can throw an error when attempting to deserialize non-self-describing formats (`bincode` results in `DeserializeAnyNotSupported`)
* Structs, tuples, tuple structs, arrays, and enums are now all de/serialized using conventional serde methods

## Migration Guide

* This PR reduces the verbosity of the scene format. Scenes will need to be updated accordingly:

```js
// Old format
{
  "type": "my_game::item::Item",
  "struct": {
    "id": {
      "type": "alloc::string::String",
      "value": "bevycraft:stone",
    },
    "tags": {
      "type": "alloc::vec::Vec<alloc::string::String>",
      "list": [
        {
          "type": "alloc::string::String",
          "value": "material"
        },
      ],
    },
}

// New format
{
  "my_game::item::Item": (
    id: "bevycraft:stone",
    tags: ["material"]
  )
}
```

[^1]: Some derives omitted for brevity.
2022-09-20 19:38:18 +00:00
targrub
bc863cec4d Derived Copy trait for bevy_input events, Serialize/Deserialize for events in bevy_input and bevy_windows, PartialEq for events in both, and Eq where possible in both. (#6023)
# Objective

Add traits to events in `bevy_input` and `bevy_windows`: `Copy`, `Serialize`/`Deserialize`, `PartialEq`, and `Eq`, as requested in https://github.com/bevyengine/bevy/issues/6022, https://github.com/bevyengine/bevy/issues/6023, https://github.com/bevyengine/bevy/issues/6024.

## Solution

Added the traits to events in `bevy_input` and `bevy_windows`.  Added dependency of `serde` in `Cargo.toml` of `bevy_input`.


## Migration Guide

If one has been `.clone()`'ing `bevy_input` events, Clippy will now complain about that.  Just remove `.clone()` to solve.

## Other Notes

Some events in `bevy_input` had `f32` fields, so `Eq` trait was not derived for them.
Some events in `bevy_windows` had `String` fields, so `Copy` trait was not derived for them.

Co-authored-by: targrub <62773321+targrub@users.noreply.github.com>
2022-09-20 18:24:00 +00:00
Carter Anderson
dcdda4cb33 Remove extra spaces from Range reflect impls (#5839)
# Objective

Remove extra spaces from Range reflect impls. Follow up to #5763 

## Solution

Remove extra spaces from Range reflect impls.
2022-08-30 21:39:48 +00:00
Gino Valente
ecc584ff23 bevy_reflect: Get owned fields (#5728)
# Objective

Sometimes it's useful to be able to retrieve all the fields of a container type so that they may be processed separately. With reflection, however, we typically only have access to references.

The only alternative is to "clone" the value using `Reflect::clone_value`. This, however, returns a Dynamic type in most cases. The solution there would be to use `FromReflect` instead, but this also has a problem in that it means we need to add `FromReflect` as an additional bound.

## Solution

Add a `drain` method to all container traits. This returns a `Vec<Box<dyn Reflect>>` (except for `Map` which returns `Vec<(Box<dyn Reflect>, Box<dyn Reflect>)>`).

This allows us to do things a lot simpler. For example, if we finished processing a struct and just need a particular value:

```rust
// === OLD === //
/// May or may not return a Dynamic*** value (even if `container` wasn't a `DynamicStruct`)
fn get_output(container: Box<dyn Struct>, output_index: usize) -> Box<dyn Reflect> {
  container.field_at(output_index).unwrap().clone_value()
}

// === NEW === //
/// Returns _exactly_ whatever was in the given struct
fn get_output(container: Box<dyn Struct>, output_index: usize) -> Box<dyn Reflect> {
  container.drain().remove(output_index).unwrap()
}
```

### Discussion

* Is `drain` the best method name? It makes sense that it "drains" all the fields and that it consumes the container in the process, but I'm open to alternatives.

---

## Changelog

* Added a `drain` method to the following traits:
  * `Struct`
  * `TupleStruct`
  * `Tuple`
  * `Array`
  * `List`
  * `Map`
  * `Enum`
2022-08-30 21:20:58 +00:00
Nathan Ward
bb2303a654 Add pop method for List trait. (#5797)
# Objective

- The reflection `List` trait does not have a `pop` function.
- Popping elements off a list is a common use case and is almost always supported by `List`-like types.

## Solution

- Add the `pop()` method to the `List` trait and add the appropriate implementations of this function.

## Migration Guide

- Any custom type that implements the `List` trait will now need to implement the `pop` method.


Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2022-08-30 21:06:32 +00:00
Marc-Stefan Cassola
e9661bea1a Implemented Reflect for all the ranges (#5806)
# Objective

Fixes #5763

## Solution

Implemented as reflect value like the current `Range`. Is there a benefit to changing everything to a reflect struct?
2022-08-30 20:51:21 +00:00
Gino Valente
7da97b4dee bevy_reflect: Remove unnecessary Clone bounds (#5783)
# Objective

Some of the reflection impls for container types had unnecessary `Clone` bounds on their generic arguments. These come from before `FromReflect` when types were instead bound by `Reflect + Clone`. With `FromReflect` this is no longer necessary.

## Solution

Removed all leftover `Clone` bounds from types that use `FromReflect` instead.

## Note

I skipped `Result<T, E>`, `HashSet<T>`, and `Range<T>` since those do not use `FromReflect`. This should probably be handled in a separate PR since it would be a breaking change.

---

## Changelog

- Remove unnecessary `Clone` bounds on reflected containers
2022-08-24 21:21:11 +00:00
Gino Valente
880ea5d4be bevy_reflect: Fix apply method for Option<T> (#5780)
# Objective

#5658 made it so that `FromReflect` was used as the bound for `T` in `Option<T>`. However, it did not use this change effectively for the implementation of `Reflect::apply` (it was still using `take`, which would fail for Dynamic types).

Additionally, the changes were not consistent with other methods within the file, such as the ones for `Vec<T>` and `HashMap<K, V>`.

## Solution

Update `Option<T>` to fallback on `FromReflect` if `take` fails, instead of wholly relying on one or the other.

I also chose to update the error messages, as they weren't all too descriptive before.

---

## Changelog

- Use `FromReflect::from_reflect` as a fallback in the `Reflect::apply` implementation for `Option<T>`
2022-08-24 20:44:35 +00:00
Gino Valente
aed3232e38 bevy_reflect: Relax bounds on Option<T> (#5658)
# Objective

The reflection impls on `Option<T>` have the bound `T: Reflect + Clone`. This means that using `FromReflect` requires `Clone` even though we can normally get away with just `FromReflect`.

## Solution

Update the bounds on `Option<T>` to match that of `Vec<T>`, where `T: FromReflect`. 

This helps remove a `Clone` implementation that may be undesired but added for the sole purpose of getting the code to compile.

---

## Changelog

* Reflection on `Option<T>` now has `T` bound by `FromReflect` rather than `Reflect + Clone`
* Added a `FromReflect` impl for `Instant`

## Migration Guide

If using `Option<T>` with Bevy's reflection API, `T` now needs to implement `FromReflect` rather than just `Clone`. This can be achieved easily by simply deriving `FromReflect`:

```rust

// OLD
#[derive(Reflect, Clone)]
struct Foo;

let reflected: Box<dyn Reflect> = Box::new(Some(Foo));

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

let reflected: Box<dyn Reflect> = Box::new(Some(Foo));
```
> Note: You can still derive `Clone`, but it's not required in order to compile.
2022-08-17 00:21:15 +00:00
maxwellodri
97fdbad9db Added reflect/from reflect impls for NonZero integer types (#5556)
# Objective

Add reflect/from reflect impls for NonZero integer types. I'm guessing these haven't been added yet because no one has needed them as of yet.
2022-08-04 22:09:49 +00:00
Gino Valente
15826d6019 bevy_reflect: Reflect enums (#4761)
# Objective

> This is a revival of #1347. Credit for the original PR should go to @Davier.

Currently, enums are treated as `ReflectRef::Value` types by `bevy_reflect`. Obviously, there needs to be better a better representation for enums using the reflection API.

## Solution

Based on prior work from @Davier, an `Enum` trait has been added as well as the ability to automatically implement it via the `Reflect` derive macro. This allows enums to be expressed dynamically:

```rust
#[derive(Reflect)]
enum Foo {
  A,
  B(usize),
  C { value: f32 },
}

let mut foo = Foo::B(123);
assert_eq!("B", foo.variant_name());
assert_eq!(1, foo.field_len());

let new_value = DynamicEnum::from(Foo::C { value: 1.23 });
foo.apply(&new_value);
assert_eq!(Foo::C{value: 1.23}, foo);
```

### Features

#### Derive Macro

Use the `#[derive(Reflect)]` macro to automatically implement the `Enum` trait for enum definitions. Optionally, you can use `#[reflect(ignore)]` with both variants and variant fields, just like you can with structs. These ignored items will not be considered as part of the reflection and cannot be accessed via reflection.

```rust
#[derive(Reflect)]
enum TestEnum {
  A,
  // Uncomment to ignore all of `B`
  // #[reflect(ignore)]
  B(usize),
  C {
    // Uncomment to ignore only field `foo` of `C`
    // #[reflect(ignore)]
    foo: f32,
    bar: bool,
  },
}
```

#### Dynamic Enums

Enums may be created/represented dynamically via the `DynamicEnum` struct. The main purpose of this struct is to allow enums to be deserialized into a partial state and to allow dynamic patching. In order to ensure conversion from a `DynamicEnum` to a concrete enum type goes smoothly, be sure to add `FromReflect` to your derive macro.

```rust
let mut value = TestEnum::A;

// Create from a concrete instance
let dyn_enum = DynamicEnum::from(TestEnum::B(123));

value.apply(&dyn_enum);
assert_eq!(TestEnum::B(123), value);

// Create a purely dynamic instance
let dyn_enum = DynamicEnum::new("TestEnum", "A", ());

value.apply(&dyn_enum);
assert_eq!(TestEnum::A, value);
```

#### Variants

An enum value is always represented as one of its variants— never the enum in its entirety.

```rust
let value = TestEnum::A;
assert_eq!("A", value.variant_name());

// Since we are using the `A` variant, we cannot also be the `B` variant
assert_ne!("B", value.variant_name());
```

All variant types are representable within the `Enum` trait: unit, struct, and tuple.

You can get the current type like:

```rust
match value.variant_type() {
  VariantType::Unit => println!("A unit variant!"),
  VariantType::Struct => println!("A struct variant!"),
  VariantType::Tuple => println!("A tuple variant!"),
}
```

> Notice that they don't contain any values representing the fields. These are purely tags.

If a variant has them, you can access the fields as well:

```rust
let mut value = TestEnum::C {
  foo: 1.23,
  bar: false
};

// Read/write specific fields
*value.field_mut("bar").unwrap() = true;

// Iterate over the entire collection of fields
for field in value.iter_fields() {
  println!("{} = {:?}", field.name(), field.value());
}
```

#### Variant Swapping

It might seem odd to group all variant types under a single trait (why allow `iter_fields` on a unit variant?), but the reason this was done ~~is to easily allow *variant swapping*.~~ As I was recently drafting up the **Design Decisions** section, I discovered that other solutions could have been made to work with variant swapping. So while there are reasons to keep the all-in-one approach, variant swapping is _not_ one of them.

```rust
let mut value: Box<dyn Enum> = Box::new(TestEnum::A);
value.set(Box::new(TestEnum::B(123))).unwrap();
```

#### Serialization

Enums can be serialized and deserialized via reflection without needing to implement `Serialize` or `Deserialize` themselves (which can save thousands of lines of generated code). Below are the ways an enum can be serialized.

> Note, like the rest of reflection-based serialization, the order of the keys in these representations is important!

##### Unit

```json
{
  "type": "my_crate::TestEnum",
  "enum": {
    "variant": "A"
  }
}
```

##### Tuple

```json
{
  "type": "my_crate::TestEnum",
  "enum": {
    "variant": "B",
    "tuple": [
      {
        "type": "usize",
        "value": 123
      }
    ]
  }
}
```

<details>
<summary>Effects on Option</summary>

This ends up making `Option` look a little ugly:

```json
{
  "type": "core::option::Option<usize>",
  "enum": {
    "variant": "Some",
    "tuple": [
      {
        "type": "usize",
        "value": 123
      }
    ]
  }
}
```


</details>

##### Struct

```json
{
  "type": "my_crate::TestEnum",
  "enum": {
    "variant": "C",
    "struct": {
      "foo": {
        "type": "f32",
        "value": 1.23
      },
      "bar": {
        "type": "bool",
        "value": false
      }
    }
  }
}
```

## Design Decisions

<details>
<summary><strong>View Section</strong></summary>

This section is here to provide some context for why certain decisions were made for this PR, alternatives that could have been used instead, and what could be improved upon in the future.

### Variant Representation

One of the biggest decisions was to decide on how to represent variants. The current design uses a "all-in-one" design where unit, tuple, and struct variants are all simultaneously represented by the `Enum` trait. This is not the only way it could have been done, though.

#### Alternatives

##### 1. Variant Traits

One way of representing variants would be to define traits for each variant, implementing them whenever an enum featured at least one instance of them. This would allow us to define variants like:

```rust
pub trait Enum: Reflect {
  fn variant(&self) -> Variant;
}

pub enum Variant<'a> {
    Unit,
    Tuple(&'a dyn TupleVariant),
    Struct(&'a dyn StructVariant),
}

pub trait TupleVariant {
  fn field_len(&self) -> usize;
  // ...
}
```

And then do things like:

```rust
fn get_tuple_len(foo: &dyn Enum) -> usize {
  match foo.variant() {
    Variant::Tuple(tuple) => tuple.field_len(),
    _ => panic!("not a tuple variant!")
  }
}
```

The reason this PR does not go with this approach is because of the fact that variants are not separate types. In other words, we cannot implement traits on specific variants— these cover the *entire* enum. This means we offer an easy footgun:

```rust
let foo: Option<i32> = None;
let my_enum = Box::new(foo) as Box<dyn TupleVariant>;
```

Here, `my_enum` contains `foo`, which is a unit variant. However, since we need to implement `TupleVariant` for `Option` as a whole, it's possible to perform such a cast. This is obviously wrong, but could easily go unnoticed. So unfortunately, this makes it not a good candidate for representing variants.

##### 2. Variant Structs

To get around the issue of traits necessarily needing to apply to both the enum and its variants, we could instead use structs that are created on a per-variant basis. This was also considered but was ultimately [[removed](71d27ab3c6) due to concerns about allocations.

 Each variant struct would probably look something like:

```rust
pub trait Enum: Reflect {
  fn variant_mut(&self) -> VariantMut;
}

pub enum VariantMut<'a> {
    Unit,
    Tuple(TupleVariantMut),
    Struct(StructVariantMut),
}

struct StructVariantMut<'a> {
  fields: Vec<&'a mut dyn Reflect>,
  field_indices: HashMap<Cow<'static, str>, usize>
}
```

This allows us to isolate struct variants into their own defined struct and define methods specifically for their use. It also prevents users from casting to it since it's not a trait. However, this is not an optimal solution. Both `field_indices` and `fields` will require an allocation (remember, a `Box<[T]>` still requires a `Vec<T>` in order to be constructed). This *might* be a problem if called frequently enough.

##### 3. Generated Structs

The original design, implemented by @Davier, instead generates structs specific for each variant. So if we had a variant path like `Foo::Bar`, we'd generate a struct named `FooBarWrapper`. This would be newtyped around the original enum and forward tuple or struct methods to the enum with the chosen variant.

Because it involved using the `Tuple` and `Struct` traits (which are also both bound on `Reflect`), this meant a bit more code had to be generated. For a single struct variant with one field, the generated code amounted to ~110LoC. However, each new field added to that variant only added ~6 more LoC.

In order to work properly, the enum had to be transmuted to the generated struct:

```rust
fn variant(&self) -> crate::EnumVariant<'_> {
  match self {
    Foo::Bar {value: i32} => {
      let wrapper_ref = unsafe { 
        std::mem::transmute::<&Self, &FooBarWrapper>(self) 
      };
      crate::EnumVariant::Struct(wrapper_ref as &dyn crate::Struct)
    }
  }
}
```

This works because `FooBarWrapper` is defined as `repr(transparent)`.

Out of all the alternatives, this would probably be the one most likely to be used again in the future. The reasons for why this PR did not continue to use it was because:

* To reduce generated code (which would hopefully speed up compile times)
* To avoid cluttering the code with generated structs not visible to the user
* To keep bevy_reflect simple and extensible (these generated structs act as proxies and might not play well with current or future systems)
* To avoid additional unsafe blocks
* My own misunderstanding of @Davier's code

That last point is obviously on me. I misjudged the code to be too unsafe and unable to handle variant swapping (which it probably could) when I was rebasing it. Looking over it again when writing up this whole section, I see that it was actually a pretty clever way of handling variant representation.

#### Benefits of All-in-One

As stated before, the current implementation uses an all-in-one approach. All variants are capable of containing fields as far as `Enum` is concerned. This provides a few benefits that the alternatives do not (reduced indirection, safer code, etc.).

The biggest benefit, though, is direct field access. Rather than forcing users to have to go through pattern matching, we grant direct access to the fields contained by the current variant. The reason we can do this is because all of the pattern matching happens internally. Getting the field at index `2` will automatically return `Some(...)` for the current variant if it has a field at that index or `None` if it doesn't (or can't).

This could be useful for scenarios where the variant has already been verified or just set/swapped (or even where the type of variant doesn't matter):

```rust
let dyn_enum: &mut dyn Enum = &mut Foo::Bar {value: 123};
// We know it's the `Bar` variant
let field = dyn_enum.field("value").unwrap();
```

Reflection is not a type-safe abstraction— almost every return value is wrapped in `Option<...>`. There are plenty of places to check and recheck that a value is what Reflect says it is. Forcing users to have to go through `match` each time they want to access a field might just be an extra step among dozens of other verification processes.

 Some might disagree, but ultimately, my view is that the benefit here is an improvement to the ergonomics and usability of reflected enums.

</details>

---

## Changelog

### Added

* Added `Enum` trait
* Added `Enum` impl to `Reflect` derive macro
* Added `DynamicEnum` struct
  * Added `DynamicVariant`
* Added `EnumInfo`
  * Added `VariantInfo`
    * Added `StructVariantInfo`
    * Added `TupleVariantInfo`
    * Added `UnitVariantInfo`
* Added serializtion/deserialization support for enums
  * Added `EnumSerializer`

* Added `VariantType`
* Added `VariantFieldIter`
* Added `VariantField`
* Added `enum_partial_eq(...)`
* Added `enum_hash(...)`

### Changed

* `Option<T>` now implements `Enum`
* `bevy_window` now depends on `bevy_reflect`
  * Implemented `Reflect` and `FromReflect` for `WindowId`
* Derive `FromReflect` on `PerspectiveProjection`
* Derive `FromReflect` on `OrthographicProjection`
* Derive `FromReflect` on `WindowOrigin`
* Derive `FromReflect` on `ScalingMode`
* Derive `FromReflect` on `DepthCalculation`


## Migration Guide

* Enums no longer need to be treated as values and usages of `#[reflect_value(...)]` can be removed or replaced by `#[reflect(...)]`
* Enums (including `Option<T>`) now take a different format when serializing. The format is described above, but this may cause issues for existing scenes that make use of enums. 

---

Also shout out to @nicopap for helping clean up some of the code here! It's a big feature so help like this is really appreciated!

Co-authored-by: Gino Valente <gino.valente.code@gmail.com>
2022-08-02 22:14:41 +00:00
Jakob Hellermann
4b191d968d remove blanket Serialize + Deserialize requirement for Reflect on generic types (#5197)
# Objective

Some generic types like `Option<T>`, `Vec<T>` and `HashMap<K, V>` implement `Reflect` when where their generic types `T`/`K`/`V` implement `Serialize + for<'de> Deserialize<'de>`.
This is so that in their `GetTypeRegistration` impl they can insert the `ReflectSerialize` and `ReflectDeserialize` type data structs.

This has the annoying side effect that if your struct contains a `Option<NonSerdeStruct>` you won't be able to derive reflect (https://github.com/bevyengine/bevy/issues/4054).

## Solution

- remove the `Serialize + Deserialize` bounds on wrapper types
  - this means that `ReflectSerialize` and `ReflectDeserialize` will no longer be inserted even for `.register::<Option<DoesImplSerde>>()`
- add `register_type_data<T, D>` shorthand for `registry.get_mut(T).insert(D::from_type<T>())`
- require users to register their specific generic types **and the serde types** separately like
```rust
        .register_type::<Option<String>>()
        .register_type_data::<Option<String>, ReflectSerialize>()
        .register_type_data::<Option<String>, ReflectDeserialize>()

```
I believe this is the best we can do for extensibility and convenience without specialization.


## Changelog

- `.register_type` for generic types like `Option<T>`, `Vec<T>`, `HashMap<K, V>` will no longer insert `ReflectSerialize` and `ReflectDeserialize` type data. Instead you need to register it separately for concrete generic types like so:
```rust
        .register_type::<Option<String>>()
        .register_type_data::<Option<String>, ReflectSerialize>()
        .register_type_data::<Option<String>, ReflectDeserialize>()
```

TODO: more docs and tweaks to the scene example to demonstrate registering generic types.
2022-07-21 14:57:37 +00:00
Jakob Hellermann
7dcfaaef67 bevy_reflect: ReflectFromPtr to create &dyn Reflect from a *const () (#4475)
# Objective

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

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

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

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

print(res.value)
```

## Solution

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

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

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

Co-authored-by: Jakob Hellermann <hellermann@sipgate.de>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2022-07-19 23:00:34 +00:00
James Liu
5498ef81fb bevy_reflect: support map insertion (#5173)
# Objective

This is a rebase of #3701 which is currently scheduled for 0.8 but is marked for adoption.

> Fixes https://github.com/bevyengine/bevy/discussions/3609

## Solution
> - add an `insert_boxed()` method on the `Map` trait
> - implement it for `HashMap` using a new `FromReflect` generic bound
> - add a `map_apply()` helper method to implement `Map::apply()`, that inserts new values instead of ignoring them


---

## Changelog
TODO

Co-authored-by: james7132 <contact@jamessliu.com>
2022-07-04 13:04:19 +00:00
PROMETHIA-27
c27a3cff6d Make Reflect safe to implement (#5010)
# Objective

Currently, `Reflect` is unsafe to implement because of a contract in which `any` and `any_mut` must return `self`, or `downcast` will cause UB. This PR makes `Reflect` safe, makes `downcast` not use unsafe, and eliminates this contract. 

## Solution

This PR adds a method to `Reflect`, `any`. It also renames the old `any` to `as_any`.
`any` now takes a `Box<Self>` and returns a `Box<dyn Any>`. 

---

## Changelog

### Added:
- `any()` method
- `represents()` method

### Changed:
- `Reflect` is now a safe trait
- `downcast()` is now safe
- The old `any` is now called `as_any`, and `any_mut` is now `as_mut_any`

## Migration Guide

- Reflect derives should not have to change anything
- Manual reflect impls will need to remove the `unsafe` keyword, add `any()` implementations, and rename the old `any` and `any_mut` to `as_any` and `as_mut_any`.
- Calls to `any`/`any_mut` must be changed to `as_any`/`as_mut_any`

## Points of discussion:

- Should renaming `any` be avoided and instead name the new method `any_box`?
- ~~Could there be a performance regression from avoiding the unsafe? I doubt it, but this change does seem to introduce redundant checks.~~
- ~~Could/should `is` and `type_id()` be implemented differently? For example, moving `is` onto `Reflect` as an `fn(&self, TypeId) -> bool`~~


Co-authored-by: PROMETHIA-27 <42193387+PROMETHIA-27@users.noreply.github.com>
2022-06-27 16:52:25 +00:00
Jakob Hellermann
218b0fd3b6 bevy_reflect: put serialize into external ReflectSerialize type (#4782)
builds on top of #4780 

# Objective

`Reflect` and `Serialize` are currently very tied together because `Reflect` has a `fn serialize(&self) -> Option<Serializable<'_>>` method. Because of that, we can either implement `Reflect` for types like `Option<T>` with `T: Serialize` and have `fn serialize` be implemented, or without the bound but having `fn serialize` return `None`.

By separating `ReflectSerialize` into a separate type (like how it already is for `ReflectDeserialize`, `ReflectDefault`), we could separately `.register::<Option<T>>()` and `.register_data::<Option<T>, ReflectSerialize>()` only if the type `T: Serialize`.

This PR does not change the registration but allows it to be changed in a future PR.

## Solution

- add the type
```rust
struct ReflectSerialize { .. }
impl<T: Reflect + Serialize> FromType<T> for ReflectSerialize { .. }
```

- remove `#[reflect(Serialize)]` special casing. 

- when serializing reflect value types, look for `ReflectSerialize` in the `TypeRegistry` instead of calling `value.serialize()`
2022-06-20 17:18:58 +00:00