Formatting of system schedule cycle detected error is very hard to follow when many systems form a cycle

[alice-i-cecile]

Bevy version

#7267, using the new schedule_v3 module.

Problem

When cycles are detected, the error message is very hard to read:

schedule contains at least 1 cycle(s) -- cycle(s) found within:
 ---- 0: ["bevy_asset::assets::Assets<bevy_animation::AnimationClip>::asset_event_system", "bevy_asset::assets::Assets<bevy_audio::audio_output::AudioSink>::asset_event_system", "bevy_asset::assets::Assets<bevy_audio::audio_source::AudioSource>::asset_event_system", "bevy_asset::assets::Assets<bevy_gltf::GltfMesh>::asset_event_system", "bevy_asset::assets::Assets<bevy_gltf::GltfPrimitive>::asset_event_system", "bevy_asset::assets::Assets<bevy_gltf::GltfNode>::asset_event_system", "bevy_asset::assets::Assets<bevy_gltf::Gltf>::asset_event_system", "bevy_asset::assets::Assets<bevy_pbr::pbr_material::StandardMaterial>::asset_event_system", "bevy_asset::assets::Assets<bevy_text::font_atlas_set::FontAtlasSet>::asset_event_system", "bevy_asset::assets::Assets<bevy_text::font::Font>::asset_event_system", "bevy_asset::assets::Assets<bevy_sprite::mesh2d::color_material::ColorMaterial>::asset_event_system", "bevy_asset::assets::Assets<bevy_sprite::texture_atlas::TextureAtlas>::asset_event_system", "bevy_asset::assets::Assets<bevy_render::texture::image::Image>::asset_event_system", "bevy_asset::assets::Assets<bevy_render::mesh::mesh::skinning::SkinnedMeshInverseBindposes>::asset_event_system", "bevy_asset::assets::Assets<bevy_render::mesh::mesh::Mesh>::asset_event_system", "bevy_asset::assets::Assets<bevy_render::render_resource::shader::Shader>::asset_event_system", "bevy_asset::assets::Assets<bevy_scene::scene::Scene>::asset_event_system", "bevy_asset::assets::Assets<bevy_scene::dynamic_scene::DynamicScene>::asset_event_system", "bevy_pbr::light::check_light_mesh_visibility", "bevy_pbr::light::update_point_light_frusta", "bevy_pbr::light::update_spot_light_frusta", "bevy_pbr::light::assign_lights_to_clusters", "bevy_pbr::light::update_directional_light_frusta", "bevy_render::view::visibility::check_visibility", "bevy_render::view::visibility::update_frusta<bevy_render::camera::projection::OrthographicProjection>", "bevy_render::view::visibility::update_frusta<bevy_render::camera::projection::PerspectiveProjection>", "bevy_render::view::visibility::update_frusta<bevy_render::camera::projection::Projection>", "bevy_ui::update::update_clipping_system", "bevy_transform::systems::propagate_transforms", "bevy_transform::systems::sync_simple_transforms", "bevy_animation::animation_player", "bevy_audio::audio_output::play_queued_audio_system<bevy_audio::audio_source::AudioSource>", "bevy_pbr::light::add_clusters", "bevy_ui::stack::ui_stack_system", "bevy_ui::flex::flex_node_system", "bevy_ui::widget::image::update_image_calculated_size_system", "bevy_ui::widget::text::text_system", "bevy_text::text2d::update_text2d_layout", "bevy_render::view::visibility::visibility_propagate_system", "bevy_render::camera::camera::camera_system<bevy_render::camera::projection::PerspectiveProjection>", "bevy_render::camera::camera::camera_system<bevy_render::camera::projection::OrthographicProjection>", "bevy_render::camera::camera::camera_system<bevy_render::camera::projection::Projection>", "bevy_winit::system::despawn_window", "bevy_winit::system::changed_window", "bevy_window::system::exit_on_all_closed", "bevy_ecs::scheduling::executor::apply_system_buffers"]

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: DependencyCycle', crates/bevy_ecs/src/scheduling/schedule.rs:181:32
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

These don't have the appropriate line breaks in the terminal.

Proposed fixes

1. Use double line breaks for each cycle, and single line breaks for each system.
2. Use short-names by default, with an option to see the full name.
3. List the total number of disconnected cycles at the top of the error message.
4. List the sets that each system is in.

Ambiguity detection recently had similar changes made; check that code for breadcrumbs.
If some of these fixes end up being more involved, submit the easy ones in their own PR.

[joseph-gio]

I wonder how hard it would be to draw the cycle in ASCII...

Something basic like

(1.)--->(2.)--->(3.)
 ^               |
 |               V
 +--------------(4.)

1. `my_path::my_system_1`
2. `my_path::my_system_4`
3. `your_path::some_system`
4. `our_path::revolution`

[alice-i-cecile]

Yeah, the other thing I really want is to list exactly what sets and constraints between sets are responsible. And then, as very much a stretch goal, link to the line numbers.

[maniwani]

It should be possible to enumerate the specific cycles in each strongly-connected component, but I don't know the exact algorithm.

We can use #[track_caller] to know where before, after, and in_set are called.