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Author SHA1 Message Date
Gino Valente
2b4180ca8f
bevy_reflect: Function reflection terminology refactor (#14813)
# Objective

One of the changes in #14704 made `DynamicFunction` effectively the same
as `DynamicClosure<'static>`. This change meant that the de facto
function type would likely be `DynamicClosure<'static>` instead of the
intended `DynamicFunction`, since the former is much more flexible.

We _could_ explore ways of making `DynamicFunction` implement `Copy`
using some unsafe code, but it likely wouldn't be worth it. And users
would likely still reach for the convenience of
`DynamicClosure<'static>` over the copy-ability of `DynamicFunction`.

The goal of this PR is to fix this confusion between the two types.

## Solution

Firstly, the `DynamicFunction` type was removed. Again, it was no
different than `DynamicClosure<'static>` so it wasn't a huge deal to
remove.

Secondly, `DynamicClosure<'env>` and `DynamicClosureMut<'env>` were
renamed to `DynamicFunction<'env>` and `DynamicFunctionMut<'env>`,
respectively.

Yes, we still ultimately kept the naming of `DynamicFunction`, but
changed its behavior to that of `DynamicClosure<'env>`. We need a term
to refer to both functions and closures, and "function" was the best
option.


[Originally](https://discord.com/channels/691052431525675048/1002362493634629796/1274091992162242710),
I was going to go with "callable" as the replacement term to encompass
both functions and closures (e.g. `DynamciCallable<'env>`). However, it
was
[suggested](https://discord.com/channels/691052431525675048/1002362493634629796/1274653581777047625)
by @SkiFire13 that the simpler "function" term could be used instead.

While "callable" is perhaps the better umbrella term—being truly
ambiguous over functions and closures— "function" is more familiar, used
more often, easier to discover, and is subjectively just
"better-sounding".

## Testing

Most changes are purely swapping type names or updating documentation,
but you can verify everything still works by running the following
command:

```
cargo test --package bevy_reflect
```
2024-08-19 21:52:36 +00:00
radiish
6ab8767d3b
reflect: implement the unique reflect rfc (#7207)
# Objective

- Implements the [Unique Reflect
RFC](https://github.com/nicopap/rfcs/blob/bevy-reflect-api/rfcs/56-better-reflect.md).

## Solution

- Implements the RFC.
- This implementation differs in some ways from the RFC:
- In the RFC, it was suggested `Reflect: Any` but `PartialReflect:
?Any`. During initial implementation I tried this, but we assume the
`PartialReflect: 'static` in a lot of places and the changes required
crept out of the scope of this PR.
- `PartialReflect::try_into_reflect` originally returned `Option<Box<dyn
Reflect>>` but i changed this to `Result<Box<dyn Reflect>, Box<dyn
PartialReflect>>` since the method takes by value and otherwise there
would be no way to recover the type. `as_full` and `as_full_mut` both
still return `Option<&(mut) dyn Reflect>`.

---

## Changelog

- Added `PartialReflect`.
- `Reflect` is now a subtrait of `PartialReflect`.
- Moved most methods on `Reflect` to the new `PartialReflect`.
- Added `PartialReflect::{as_partial_reflect, as_partial_reflect_mut,
into_partial_reflect}`.
- Added `PartialReflect::{try_as_reflect, try_as_reflect_mut,
try_into_reflect}`.
- Added `<dyn PartialReflect>::{try_downcast_ref, try_downcast_mut,
try_downcast, try_take}` supplementing the methods on `dyn Reflect`.

## Migration Guide

- Most instances of `dyn Reflect` should be changed to `dyn
PartialReflect` which is less restrictive, however trait bounds should
generally stay as `T: Reflect`.
- The new `PartialReflect::{as_partial_reflect, as_partial_reflect_mut,
into_partial_reflect, try_as_reflect, try_as_reflect_mut,
try_into_reflect}` methods as well as `Reflect::{as_reflect,
as_reflect_mut, into_reflect}` will need to be implemented for manual
implementors of `Reflect`.

## Future Work

- This PR is designed to be followed up by another "Unique Reflect Phase
2" that addresses the following points:
- Investigate making serialization revolve around `Reflect` instead of
`PartialReflect`.
- [Remove the `try_*` methods on `dyn PartialReflect` since they are
stop
gaps](https://github.com/bevyengine/bevy/pull/7207#discussion_r1083476050).
- Investigate usages like `ReflectComponent`. In the places they
currently use `PartialReflect`, should they be changed to use `Reflect`?
- Merging this opens the door to lots of reflection features we haven't
been able to implement.
- We could re-add [the `Reflectable`
trait](8e3488c880/crates/bevy_reflect/src/reflect.rs (L337-L342))
and make `FromReflect` a requirement to improve [`FromReflect`
ergonomics](https://github.com/bevyengine/rfcs/pull/59). This is
currently not possible because dynamic types cannot sensibly be
`FromReflect`.
  - Since this is an alternative to #5772, #5781 would be made cleaner.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Gino Valente <49806985+MrGVSV@users.noreply.github.com>
2024-08-12 17:01:41 +00:00
Gino Valente
af865e76a3
bevy_reflect: Improve DynamicFunction ergonomics (#14201)
# Objective

Many functions can be converted to `DynamicFunction` using
`IntoFunction`. Unfortunately, we are limited by Rust itself and the
implementations are far from exhaustive. For example, we can't convert
functions with more than 16 arguments. Additionally, we can't handle
returns with lifetimes not tied to the lifetime of the first argument.

In such cases, users will have to create their `DynamicFunction`
manually.

Let's take the following function:

```rust
fn get(index: usize, list: &Vec<String>) -> &String {
    &list[index]
}
```

This function cannot be converted to a `DynamicFunction` via
`IntoFunction` due to the lifetime of the return value being tied to the
second argument. Therefore, we need to construct the `DynamicFunction`
manually:

```rust
DynamicFunction::new(
    |mut args, info| {
        let list = args
            .pop()
            .unwrap()
            .take_ref::<Vec<String>>(&info.args()[1])?;
        let index = args.pop().unwrap().take_owned::<usize>(&info.args()[0])?;
        Ok(Return::Ref(get(index, list)))
    },
    FunctionInfo::new()
        .with_name("get")
        .with_args(vec![
            ArgInfo:🆕:<usize>(0).with_name("index"),
            ArgInfo:🆕:<&Vec<String>>(1).with_name("list"),
        ])
        .with_return_info(ReturnInfo:🆕:<&String>()),
);
```

While still a small and straightforward snippet, there's a decent amount
going on here. There's a lot of room for improvements when it comes to
ergonomics and readability.

The goal of this PR is to address those issues.

## Solution

Improve the ergonomics and readability of manually created
`DynamicFunction`s.

Some of the major changes:
1. Removed the need for `&ArgInfo` when reifying arguments (i.e. the
`&info.args()[1]` calls)
2. Added additional `pop` methods on `ArgList` to handle both popping
and casting
3. Added `take` methods on `ArgList` for taking the arguments out in
order
4. Removed the need for `&FunctionInfo` in the internal closure (Change
1 made it no longer necessary)
5. Added methods to automatically handle generating `ArgInfo` and
`ReturnInfo`

With all these changes in place, we get something a lot nicer to both
write and look at:

```rust
DynamicFunction::new(
    |mut args| {
        let index = args.take::<usize>()?;
        let list = args.take::<&Vec<String>>()?;
        Ok(Return::Ref(get(index, list)))
    },
    FunctionInfo::new()
        .with_name("get")
        .with_arg::<usize>("index")
        .with_arg::<&Vec<String>>("list")
        .with_return::<&String>(),
);
```

Alternatively, to rely on type inference for taking arguments, you could
do:

```rust
DynamicFunction::new(
    |mut args| {
        let index = args.take_owned()?;
        let list = args.take_ref()?;
        Ok(Return::Ref(get(index, list)))
    },
    FunctionInfo::new()
        .with_name("get")
        .with_arg::<usize>("index")
        .with_arg::<&Vec<String>>("list")
        .with_return::<&String>(),
);
```

## Testing

You can test locally by running:

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

---

## Changelog

- Removed `&ArgInfo` argument from `FromArg::from_arg` trait method
- Removed `&ArgInfo` argument from `Arg::take_***` methods
- Added `ArgValue`
- `Arg` is now a struct containing an `ArgValue` and an argument `index`
- `Arg::take_***` methods now require `T` is also `TypePath`
- Added `Arg::new`, `Arg::index`, `Arg::value`, `Arg::take_value`, and
`Arg::take` methods
- Replaced `ArgId` in `ArgError` with just the argument `index`
- Added `ArgError::EmptyArgList`
- Renamed `ArgList::push` to `ArgList::push_arg`
- Added `ArgList::pop_arg`, `ArgList::pop_owned`, `ArgList::pop_ref`,
and `ArgList::pop_mut`
- Added `ArgList::take_arg`, `ArgList::take_owned`, `ArgList::take_ref`,
`ArgList::take_mut`, and `ArgList::take`
- `ArgList::pop` is now generic
- Renamed `FunctionError::InvalidArgCount` to
`FunctionError::ArgCountMismatch`
- The closure given to `DynamicFunction::new` no longer has a
`&FunctionInfo` argument
- Added `FunctionInfo::with_arg`
- Added `FunctionInfo::with_return`

## Internal Migration Guide

> [!important]
> Function reflection was introduced as part of the 0.15 dev cycle. This
migration guide was written for developers relying on `main` during this
cycle, and is not a breaking change coming from 0.14.

* The `FromArg::from_arg` trait method and the `Arg::take_***` methods
no longer take a `&ArgInfo` argument.
* What used to be `Arg` is now `ArgValue`. `Arg` is now a struct which
contains an `ArgValue`.
* `Arg::take_***` methods now require `T` is also `TypePath`
* Instances of `id: ArgId` in `ArgError` have been replaced with `index:
usize`
* `ArgList::push` is now `ArgList::push_arg`. It also takes the new
`ArgValue` type.
* `ArgList::pop` has become `ArgList::pop_arg` and now returns
`ArgValue`. `Arg::pop` now takes a generic type and downcasts to that
type. It's recommended to use `ArgList::take` and friends instead since
they allow removing the arguments from the list in the order they were
pushed (rather than reverse order).
* `FunctionError::InvalidArgCount` is now
`FunctionError::ArgCountMismatch`
* The closure given to `DynamicFunction::new` no longer has a
`&FunctionInfo` argument. This argument can be removed.
2024-07-16 13:01:52 +00:00
Gino Valente
1042f09c2e
bevy_reflect: Add DynamicClosure and DynamicClosureMut (#14141)
# Objective

As mentioned in
[this](https://github.com/bevyengine/bevy/pull/13152#issuecomment-2198387297)
comment, creating a function registry (see #14098) is a bit difficult
due to the requirements of `DynamicFunction`. Internally, a
`DynamicFunction` contains a `Box<dyn FnMut>` (the function that reifies
reflected arguments and calls the actual function), which requires `&mut
self` in order to be called.

This means that users would require a mutable reference to the function
registry for it to be useful— which isn't great. And they can't clone
the `DynamicFunction` either because cloning an `FnMut` isn't really
feasible (wrapping it in an `Arc` would allow it to be cloned but we
wouldn't be able to call the clone since we need a mutable reference to
the `FnMut`, which we can't get with multiple `Arc`s still alive,
requiring us to also slap in a `Mutex`, which adds additional overhead).

And we don't want to just replace the `dyn FnMut` with `dyn Fn` as that
would prevent reflecting closures that mutate their environment.

Instead, we need to introduce a new type to split the requirements of
`DynamicFunction`.

## Solution

Introduce new types for representing closures.

Specifically, this PR introduces `DynamicClosure` and
`DynamicClosureMut`. Similar to how `IntoFunction` exists for
`DynamicFunction`, two new traits were introduced: `IntoClosure` and
`IntoClosureMut`.

Now `DynamicFunction` stores a `dyn Fn` with a `'static` lifetime.
`DynamicClosure` also uses a `dyn Fn` but has a lifetime, `'env`, tied
to its environment. `DynamicClosureMut` is most like the old
`DynamicFunction`, keeping the `dyn FnMut` and also typing its lifetime,
`'env`, to the environment

Here are some comparison tables:

|   | `DynamicFunction` | `DynamicClosure` | `DynamicClosureMut` |
| - | ----------------- | ---------------- | ------------------- |
| Callable with `&self` |  |  |  |
| Callable with `&mut self` |  |  |  |
| Allows for non-`'static` lifetimes |  |  |  |

|   | `IntoFunction` | `IntoClosure` | `IntoClosureMut` |
| - | -------------- | ------------- | ---------------- |
| Convert `fn` functions |  |  |  |
| Convert `fn` methods |  |  |  |
| Convert anonymous functions |  |  |  |
| Convert closures that capture immutable references |  |  |  |
| Convert closures that capture mutable references |  |  |  |
| Convert closures that capture owned values | [^1] |  |  |

[^1]: Due to limitations in Rust, `IntoFunction` can't be implemented
for just functions (unless we forced users to manually coerce them to
function pointers first). So closures that meet the trait requirements
_can technically_ be converted into a `DynamicFunction` as well. To both
future-proof and reduce confusion, though, we'll just pretend like this
isn't a thing.

```rust
let mut list: Vec<i32> = vec![1, 2, 3];

// `replace` is a closure that captures a mutable reference to `list`
let mut replace = |index: usize, value: i32| -> i32 {
  let old_value = list[index];
  list[index] = value;
  old_value
};

// Convert the closure into a dynamic closure using `IntoClosureMut::into_closure_mut`
let mut func: DynamicClosureMut = replace.into_closure_mut();

// Dynamically call the closure:
let args = ArgList::default().push_owned(1_usize).push_owned(-2_i32);
let value = func.call_once(args).unwrap().unwrap_owned();

// Check the result:
assert_eq!(value.take::<i32>().unwrap(), 2);
assert_eq!(list, vec![1, -2, 3]);
```

### `ReflectFn`/`ReflectFnMut`

To make extending the function reflection system easier (the blanket
impls for `IntoFunction`, `IntoClosure`, and `IntoClosureMut` are all
incredibly short), this PR generalizes callables with two new traits:
`ReflectFn` and `ReflectFnMut`.

These traits mimic `Fn` and `FnMut` but allow for being called via
reflection. In fact, their blanket implementations are identical save
for `ReflectFn` being implemented over `Fn` types and `ReflectFnMut`
being implemented over `FnMut` types.

And just as `Fn` is a subtrait of `FnMut`, `ReflectFn` is a subtrait of
`ReflectFnMut`. So anywhere that expects a `ReflectFnMut` can also be
given a `ReflectFn`.

To reiterate, these traits aren't 100% necessary. They were added in
purely for extensibility. If we decide to split things up differently or
add new traits/types in the future, then those changes should be much
simpler to implement.

### `TypedFunction`

Because of the split into `ReflectFn` and `ReflectFnMut`, we needed a
new way to access the function type information. This PR moves that
concept over into `TypedFunction`.

Much like `Typed`, this provides a way to access a function's
`FunctionInfo`.

By splitting this trait out, it helps to ensure the other traits are
focused on a single responsibility.

### Internal Macros

The original function PR (#13152) implemented `IntoFunction` using a
macro which was passed into an `all_tuples!` macro invocation. Because
we needed the same functionality for these new traits, this PR has
copy+pasted that code for `ReflectFn`, `ReflectFnMut`, and
`TypedFunction`— albeit with some differences between them.

Originally, I was going to try and macro-ify the impls and where clauses
such that we wouldn't have to straight up duplicate a lot of this logic.
However, aside from being more complex in general, autocomplete just
does not play nice with such heavily nested macros (tried in both
RustRover and VSCode). And both of those problems told me that it just
wasn't worth it: we need to ensure the crate is easily maintainable,
even at the cost of duplicating code.

So instead, I made sure to simplify the macro code by removing all
fully-qualified syntax and cutting the where clauses down to the bare
essentials, which helps to clean up a lot of the visual noise. I also
tried my best to document the macro logic in certain areas (I may even
add a bit more) to help with maintainability for future devs.

### Documentation

Documentation for this module was a bit difficult for me. So many of
these traits and types are very interconnected. And each trait/type has
subtle differences that make documenting it in a single place, like at
the module level, difficult to do cleanly. Describing the valid
signatures is also challenging to do well.

Hopefully what I have here is okay. I think I did an okay job, but let
me know if there any thoughts on ways to improve it. We can also move
such a task to a followup PR for more focused discussion.

## Testing

You can test locally by running:

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

---

## Changelog

- Added `DynamicClosure` struct
- Added `DynamicClosureMut` struct
- Added `IntoClosure` trait
- Added `IntoClosureMut` trait
- Added `ReflectFn` trait
- Added `ReflectFnMut` trait
- Added `TypedFunction` trait
- `IntoFunction` now only works for standard Rust functions
- `IntoFunction` no longer takes a lifetime parameter
- `DynamicFunction::call` now only requires `&self`
- Removed `DynamicFunction::call_once`
- Changed the `IntoReturn::into_return` signature to include a where
clause

## Internal Migration Guide

> [!important]
> Function reflection was introduced as part of the 0.15 dev cycle. This
migration guide was written for developers relying on `main` during this
cycle, and is not a breaking change coming from 0.14.

### `IntoClosure`

`IntoFunction` now only works for standard Rust functions. Calling
`IntoFunction::into_function` on a closure that captures references to
its environment (either mutable or immutable), will no longer compile.

Instead, you will need to use either `IntoClosure::into_closure` to
create a `DynamicClosure` or `IntoClosureMut::into_closure_mut` to
create a `DynamicClosureMut`, depending on your needs:

```rust
let punct = String::from("!");
let print = |value: String| {
    println!("{value}{punct}");
};

// BEFORE
let func: DynamicFunction = print.into_function();

// AFTER
let func: DynamicClosure = print.into_closure();
```

### `IntoFunction` lifetime

Additionally, `IntoFunction` no longer takes a lifetime parameter as it
always expects a `'static` lifetime. Usages will need to remove any
lifetime parameters:

```rust
// BEFORE
fn execute<'env, F: IntoFunction<'env, Marker>, Marker>(f: F) {/* ... */}

// AFTER
fn execute<F: IntoFunction<Marker>, Marker>(f: F) {/* ... */}
```

### `IntoReturn`

`IntoReturn::into_return` now has a where clause. Any manual
implementors will need to add this where clause to their implementation.
2024-07-16 03:22:43 +00:00