ambiguity_detection.rs

//! A test to confirm that `bevy` doesn't regress its system ambiguities count when using [`DefaultPlugins`].
//! This is run in CI.
//!
//! Note that because this test requires rendering, it isn't actually an integration test!
//! Instead, it's secretly an example: you can run this test manually using `cargo run --example ambiguity_detection`.

use bevy::{
    ecs::schedule::{InternedScheduleLabel, LogLevel, ScheduleBuildSettings},
    platform::collections::HashMap,
    prelude::*,
    render::{pipelined_rendering::PipelinedRenderingPlugin, RenderPlugin},
};

fn main() {
    let mut app = App::new();
    app.add_plugins(
        DefaultPlugins
            .build()
            .set(RenderPlugin {
                // llvmpipe driver can cause segfaults when aborting the binary while pipelines are being
                // compiled (which happens very quickly in this example since we only run for a single
                // frame). Synchronous pipeline compilation helps prevent these segfaults as the
                // rendering thread blocks on these pipeline compilations.
                synchronous_pipeline_compilation: true,
                ..Default::default()
            })
            // We also have to disable pipelined rendering to ensure the test doesn't end while the
            // rendering frame is still executing in another thread.
            .disable::<PipelinedRenderingPlugin>(),
    );

    let main_app = app.main_mut();
    configure_ambiguity_detection(main_app);

    // Ambiguities in the RenderApp are currently allowed.
    // Eventually, we should forbid these: see https://github.com/bevyengine/bevy/issues/7386
    // Uncomment the lines below to show the current ambiguities in the RenderApp.
    // let sub_app = app.sub_app_mut(bevy_render::RenderApp);
    // configure_ambiguity_detection(sub_app);

    app.finish();
    app.cleanup();
    app.update();

    let main_app_ambiguities = count_ambiguities(app.main());
    assert_eq!(
        main_app_ambiguities.total(),
        0,
        "Main app has unexpected ambiguities among the following schedules: \n{main_app_ambiguities:#?}.",
    );
}

/// Contains the number of conflicting systems per schedule.
#[derive(Debug, Deref, DerefMut)]
struct AmbiguitiesCount(pub HashMap<InternedScheduleLabel, usize>);

impl AmbiguitiesCount {
    fn total(&self) -> usize {
        self.values().sum()
    }
}

fn configure_ambiguity_detection(sub_app: &mut SubApp) {
    let mut schedules = sub_app.world_mut().resource_mut::<Schedules>();
    for (_, schedule) in schedules.iter_mut() {
        schedule.set_build_settings(ScheduleBuildSettings {
            // NOTE: you can change this to `LogLevel::Ignore` to easily see the current number of ambiguities.
            ambiguity_detection: LogLevel::Warn,
            use_shortnames: false,
            ..default()
        });
    }
}

/// Returns the number of conflicting systems per schedule.
fn count_ambiguities(sub_app: &SubApp) -> AmbiguitiesCount {
    let schedules = sub_app.world().resource::<Schedules>();
    let mut ambiguities = <HashMap<_, _>>::default();
    for (_, schedule) in schedules.iter() {
        let ambiguities_in_schedule = schedule.graph().conflicting_systems().len();
        ambiguities.insert(schedule.label(), ambiguities_in_schedule);
    }
    AmbiguitiesCount(ambiguities)
}