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Document all members of bevy_dynamic_plugin (#12029)

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# Objective

- Some members of `bevy_dynamic_plugin` are not documented.
- Part of #3492.

## Solution

- Add documentation to members missing it in `bevy_dynamic_plugin`.
- Update existing documentation for clarity and formatting.

---

## Changelog

- Completely document `bevy_dynamic_plugin`.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: James Liu <contact@jamessliu.com>
This commit is contained in:
BD103 2024-02-22 08:28:52 -05:00 committed by GitHub
parent 33c7a2251e
commit 44a0e3f947
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2 changed files with 35 additions and 10 deletions
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22
crates/bevy_dynamic_plugin/src/lib.rs
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@ -1,5 +1,23 @@
// FIXME(3492): remove once docs are ready
#![allow(missing_docs)]
//! Bevy's dynamic plugin loading functionality.
//!
//! This crate allows loading dynamic libraries (`.dylib`, `.so`) that export a single
//! [`Plugin`](bevy_app::Plugin). For usage, see [`dynamically_load_plugin`].
//!
//! Note that dynamic linking and loading is inherently unsafe because it allows executing foreign
//! code. Additionally, Rust does not have a stable ABI and may produce
//! incompatible libraries across Rust versions, or even subsequent compilations. This will not work
//! well in scenarios such as modding, but can work if the dynamic plugins and the main app are
//! built at the same time, such as with Downloadable Content (DLC) packs.
//!
//! You may be interested in these safer alternatives:
//!
//! - [Bevy Assets - Scripting]: Scripting and modding libraries for Bevy
//! - [Bevy Assets - Development tools]: Hot reloading and other development functionality
//! - [`stabby`]: Stable Rust ABI
//!
//! [Bevy Assets - Scripting]: https://bevyengine.org/assets/#scripting
//! [Bevy Assets - Development tools]: https://bevyengine.org/assets/#development-tools
//! [`stabby`]: https://github.com/ZettaScaleLabs/stabby
mod loader;

23
crates/bevy_dynamic_plugin/src/loader.rs
View file

@ -7,8 +7,10 @@ use bevy_app::{App, CreatePlugin, Plugin};
/// Errors that can occur when loading a dynamic plugin
#[derive(Debug, Error)]
pub enum DynamicPluginLoadError {
/// An error occurred when loading a dynamic library.
#[error("cannot load library for dynamic plugin: {0}")]
Library(#[source] libloading::Error),
/// An error occurred when loading a library without a valid Bevy plugin.
#[error("dynamic library does not contain a valid Bevy dynamic plugin")]
Plugin(#[source] libloading::Error),
}
@ -18,22 +20,22 @@ pub enum DynamicPluginLoadError {
///
/// # Safety
///
/// The specified plugin must be linked against the exact same libbevy.so as this program.
/// The specified plugin must be linked against the exact same `libbevy.so` as this program.
/// In addition the `_bevy_create_plugin` symbol must not be manually created, but instead created
/// by deriving `DynamicPlugin` on a unit struct implementing [`Plugin`].
///
/// Dynamically loading plugins is orchestrated through dynamic linking. When linking against foreign
/// code, initialization routines may be run (as well as termination routines when the program exits).
/// The caller of this function is responsible for ensuring these routines are sound. For more
/// information, please see the safety section of [`libloading::Library::new`].
/// Dynamically loading plugins is orchestrated through dynamic linking. When linking against
/// foreign code, initialization routines may be run (as well as termination routines when the
/// program exits). The caller of this function is responsible for ensuring these routines are
/// sound. For more information, please see the safety section of [`libloading::Library::new`].
pub unsafe fn dynamically_load_plugin<P: AsRef<OsStr>>(
path: P,
) -> Result<(Library, Box<dyn Plugin>), DynamicPluginLoadError> {
// SAFETY: Caller must follow the safety requirements of Library::new.
let lib = unsafe { Library::new(path).map_err(DynamicPluginLoadError::Library)? };
// SAFETY: Loaded plugins are not allowed to specify `_bevy_create_plugin` symbol manually, but must
// instead automatically generate it through `DynamicPlugin`.
// SAFETY: Loaded plugins are not allowed to specify `_bevy_create_plugin` symbol manually, but
// must instead automatically generate it through `DynamicPlugin`.
let func: Symbol<CreatePlugin> = unsafe {
lib.get(b"_bevy_create_plugin")
.map_err(DynamicPluginLoadError::Plugin)?
@ -46,10 +48,15 @@ pub unsafe fn dynamically_load_plugin<P: AsRef<OsStr>>(
Ok((lib, plugin))
}
/// An extension trait for [`App`] that allows loading dynamic plugins.
pub trait DynamicPluginExt {
/// Dynamically links a plugin at the given path, registering the plugin.
///
/// For more details, see [`dynamically_load_plugin`].
///
/// # Safety
///
/// Same as [`dynamically_load_plugin`].
/// See [`dynamically_load_plugin`]'s safety section.
unsafe fn load_plugin<P: AsRef<OsStr>>(&mut self, path: P) -> &mut Self;
}