bevy/crates/bevy_hierarchy/src/valid_parent_check_plugin.rs
Carter Anderson dcc03724a5 Base Sets (#7466)
# Objective

NOTE: This depends on #7267 and should not be merged until #7267 is merged. If you are reviewing this before that is merged, I highly recommend viewing the Base Sets commit instead of trying to find my changes amongst those from #7267.

"Default sets" as described by the [Stageless RFC](https://github.com/bevyengine/rfcs/pull/45) have some [unfortunate consequences](https://github.com/bevyengine/bevy/discussions/7365).

## Solution

This adds "base sets" as a variant of `SystemSet`:

A set is a "base set" if `SystemSet::is_base` returns `true`. Typically this will be opted-in to using the `SystemSet` derive:

```rust
#[derive(SystemSet, Clone, Hash, Debug, PartialEq, Eq)]
#[system_set(base)]
enum MyBaseSet {
  A,
  B,
}
``` 

**Base sets are exclusive**: a system can belong to at most one "base set". Adding a system to more than one will result in an error. When possible we fail immediately during system-config-time with a nice file + line number. For the more nested graph-ey cases, this will fail at the final schedule build. 

**Base sets cannot belong to other sets**: this is where the word "base" comes from

Systems and Sets can only be added to base sets using `in_base_set`. Calling `in_set` with a base set will fail. As will calling `in_base_set` with a normal set.

```rust
app.add_system(foo.in_base_set(MyBaseSet::A))
       // X must be a normal set ... base sets cannot be added to base sets
       .configure_set(X.in_base_set(MyBaseSet::A))
```

Base sets can still be configured like normal sets:

```rust
app.add_system(MyBaseSet::B.after(MyBaseSet::Ap))
``` 

The primary use case for base sets is enabling a "default base set":

```rust
schedule.set_default_base_set(CoreSet::Update)
  // this will belong to CoreSet::Update by default
  .add_system(foo)
  // this will override the default base set with PostUpdate
  .add_system(bar.in_base_set(CoreSet::PostUpdate))
```

This allows us to build apis that work by default in the standard Bevy style. This is a rough analog to the "default stage" model, but it use the new "stageless sets" model instead, with all of the ordering flexibility (including exclusive systems) that it provides.

---

## Changelog

- Added "base sets" and ported CoreSet to use them.

## Migration Guide

TODO
2023-02-06 03:10:08 +00:00

106 lines
3.5 KiB
Rust

use std::marker::PhantomData;
use bevy_app::{App, CoreSet, Plugin};
use bevy_core::Name;
use bevy_ecs::prelude::*;
use bevy_log::warn;
use bevy_utils::{get_short_name, HashSet};
use crate::Parent;
/// When enabled, runs [`check_hierarchy_component_has_valid_parent<T>`].
///
/// This resource is added by [`ValidParentCheckPlugin<T>`].
/// It is enabled on debug builds and disabled in release builds by default,
/// you can update this resource at runtime to change the default behavior.
#[derive(Resource)]
pub struct ReportHierarchyIssue<T> {
/// Whether to run [`check_hierarchy_component_has_valid_parent<T>`].
pub enabled: bool,
_comp: PhantomData<fn(T)>,
}
impl<T> ReportHierarchyIssue<T> {
/// Constructs a new object
pub fn new(enabled: bool) -> Self {
ReportHierarchyIssue {
enabled,
_comp: Default::default(),
}
}
}
impl<T> PartialEq for ReportHierarchyIssue<T> {
fn eq(&self, other: &Self) -> bool {
self.enabled == other.enabled
}
}
impl<T> Default for ReportHierarchyIssue<T> {
fn default() -> Self {
Self {
enabled: cfg!(debug_assertions),
_comp: PhantomData,
}
}
}
/// System to print a warning for each `Entity` with a `T` component
/// which parent hasn't a `T` component.
///
/// Hierarchy propagations are top-down, and limited only to entities
/// with a specific component (such as `ComputedVisibility` and `GlobalTransform`).
/// This means that entities with one of those component
/// and a parent without the same component is probably a programming error.
/// (See B0004 explanation linked in warning message)
pub fn check_hierarchy_component_has_valid_parent<T: Component>(
parent_query: Query<
(Entity, &Parent, Option<&Name>),
(With<T>, Or<(Changed<Parent>, Added<T>)>),
>,
component_query: Query<(), With<T>>,
mut already_diagnosed: Local<HashSet<Entity>>,
) {
for (entity, parent, name) in &parent_query {
let parent = parent.get();
if !component_query.contains(parent) && !already_diagnosed.contains(&entity) {
already_diagnosed.insert(entity);
warn!(
"warning[B0004]: {name} with the {ty_name} component has a parent without {ty_name}.\n\
This will cause inconsistent behaviors! See https://bevyengine.org/learn/errors/#b0004",
ty_name = get_short_name(std::any::type_name::<T>()),
name = name.map_or("An entity".to_owned(), |s| format!("The {s} entity")),
);
}
}
}
/// Run criteria that only allows running when [`ReportHierarchyIssue<T>`] is enabled.
pub fn on_hierarchy_reports_enabled<T>(report: Res<ReportHierarchyIssue<T>>) -> bool
where
T: Component,
{
report.enabled
}
/// Print a warning for each `Entity` with a `T` component
/// whose parent doesn't have a `T` component.
///
/// See [`check_hierarchy_component_has_valid_parent`] for details.
pub struct ValidParentCheckPlugin<T: Component>(PhantomData<fn() -> T>);
impl<T: Component> Default for ValidParentCheckPlugin<T> {
fn default() -> Self {
Self(PhantomData)
}
}
impl<T: Component> Plugin for ValidParentCheckPlugin<T> {
fn build(&self, app: &mut App) {
app.init_resource::<ReportHierarchyIssue<T>>().add_system(
check_hierarchy_component_has_valid_parent::<T>
.run_if(resource_equals(ReportHierarchyIssue::<T>::new(true)))
.in_base_set(CoreSet::Last),
);
}
}