From 8258d5675d69169227e6102391f410aaa443c1a2 Mon Sep 17 00:00:00 2001
From: targrub <targrub@gmail.com>
Date: Sun, 9 Oct 2022 15:17:26 -0400
Subject: [PATCH 1/8] Implementations of Debug for App, System, Stage,
 Schedule, and related.

---
 crates/bevy_app/src/app.rs                    | 20 ++++++++++++++--
 crates/bevy_ecs/src/archetype.rs              | 11 +++++++--
 crates/bevy_ecs/src/schedule/executor.rs      |  9 ++++++-
 crates/bevy_ecs/src/schedule/mod.rs           |  2 +-
 crates/bevy_ecs/src/schedule/run_criteria.rs  | 24 +++++++++++++++++--
 crates/bevy_ecs/src/schedule/stage.rs         |  8 +++++++
 .../bevy_ecs/src/schedule/system_container.rs |  7 ++++++
 .../src/schedule/system_descriptor.rs         |  1 +
 crates/bevy_ecs/src/system/system.rs          | 19 +++++++++++++++
 9 files changed, 93 insertions(+), 8 deletions(-)

diff --git a/crates/bevy_app/src/app.rs b/crates/bevy_app/src/app.rs
index e71cda2229307..79388fba23902 100644
--- a/crates/bevy_app/src/app.rs
+++ b/crates/bevy_app/src/app.rs
@@ -12,7 +12,7 @@ use bevy_ecs::{
     world::World,
 };
 use bevy_utils::{tracing::debug, HashMap};
-use std::fmt::Debug;
+use core::fmt::Debug;
 
 #[cfg(feature = "trace")]
 use bevy_utils::tracing::info_span;
@@ -25,7 +25,7 @@ bevy_utils::define_label!(
 
 /// The [`Resource`] that stores the [`App`]'s [`TypeRegistry`](bevy_reflect::TypeRegistry).
 #[cfg(feature = "bevy_reflect")]
-#[derive(Resource, Clone, Deref, DerefMut, Default)]
+#[derive(Debug, Resource, Clone, Deref, DerefMut, Default)]
 pub struct AppTypeRegistry(pub bevy_reflect::TypeRegistryArc);
 
 #[allow(clippy::needless_doctest_main)]
@@ -70,12 +70,28 @@ pub struct App {
     sub_apps: HashMap<AppLabelId, SubApp>,
 }
 
+impl Debug for App {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "App {{sub_apps: ")?;
+        f.debug_map()
+            .entries(self.sub_apps.iter().map(|(k, v)| (k, v)))
+            .finish()?;
+        write!(f, "}}")
+    }
+}
+
 /// Each `SubApp` has its own [`Schedule`] and [`World`], enabling a separation of concerns.
 struct SubApp {
     app: App,
     runner: Box<dyn Fn(&mut World, &mut App)>,
 }
 
+impl Debug for SubApp {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "SubApp")
+    }
+}
+
 impl Default for App {
     fn default() -> Self {
         let mut app = App::empty();
diff --git a/crates/bevy_ecs/src/archetype.rs b/crates/bevy_ecs/src/archetype.rs
index cf81b5b633a2e..358ae8099f96e 100644
--- a/crates/bevy_ecs/src/archetype.rs
+++ b/crates/bevy_ecs/src/archetype.rs
@@ -32,11 +32,13 @@ impl ArchetypeId {
     }
 }
 
+#[derive(Debug)]
 pub(crate) enum ComponentStatus {
     Added,
     Mutated,
 }
 
+#[derive(Debug)]
 pub struct AddBundle {
     pub archetype_id: ArchetypeId,
     pub(crate) bundle_status: Vec<ComponentStatus>,
@@ -56,7 +58,7 @@ pub struct AddBundle {
 /// yet.
 ///
 /// [`World`]: crate::world::World
-#[derive(Default)]
+#[derive(Debug, Default)]
 pub struct Edges {
     add_bundle: SparseArray<BundleId, AddBundle>,
     remove_bundle: SparseArray<BundleId, Option<ArchetypeId>>,
@@ -118,21 +120,25 @@ impl Edges {
     }
 }
 
+#[derive(Debug)]
 struct TableInfo {
     id: TableId,
     entity_rows: Vec<usize>,
 }
 
+#[derive(Debug)]
 pub(crate) struct ArchetypeSwapRemoveResult {
     pub(crate) swapped_entity: Option<Entity>,
     pub(crate) table_row: usize,
 }
 
+#[derive(Debug)]
 pub(crate) struct ArchetypeComponentInfo {
     pub(crate) storage_type: StorageType,
     pub(crate) archetype_component_id: ArchetypeComponentId,
 }
 
+#[derive(Debug)]
 pub struct Archetype {
     id: ArchetypeId,
     entities: Vec<Entity>,
@@ -346,7 +352,7 @@ impl ArchetypeGeneration {
     }
 }
 
-#[derive(Hash, PartialEq, Eq)]
+#[derive(Debug, Hash, PartialEq, Eq)]
 pub struct ArchetypeIdentity {
     table_components: Box<[ComponentId]>,
     sparse_set_components: Box<[ComponentId]>,
@@ -378,6 +384,7 @@ impl SparseSetIndex for ArchetypeComponentId {
     }
 }
 
+#[derive(Debug)]
 pub struct Archetypes {
     pub(crate) archetypes: Vec<Archetype>,
     pub(crate) archetype_component_count: usize,
diff --git a/crates/bevy_ecs/src/schedule/executor.rs b/crates/bevy_ecs/src/schedule/executor.rs
index 4e649d47086f9..ef0cb45fb229d 100644
--- a/crates/bevy_ecs/src/schedule/executor.rs
+++ b/crates/bevy_ecs/src/schedule/executor.rs
@@ -1,4 +1,5 @@
 use crate::{schedule::SystemContainer, world::World};
+use core::fmt::Debug;
 use downcast_rs::{impl_downcast, Downcast};
 
 pub trait ParallelSystemExecutor: Downcast + Send + Sync {
@@ -8,9 +9,15 @@ pub trait ParallelSystemExecutor: Downcast + Send + Sync {
     fn run_systems(&mut self, systems: &mut [SystemContainer], world: &mut World);
 }
 
+impl Debug for dyn ParallelSystemExecutor {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "dyn ParallelSystemExecutor")
+    }
+}
+
 impl_downcast!(ParallelSystemExecutor);
 
-#[derive(Default)]
+#[derive(Debug, Default)]
 pub struct SingleThreadedExecutor;
 
 impl ParallelSystemExecutor for SingleThreadedExecutor {
diff --git a/crates/bevy_ecs/src/schedule/mod.rs b/crates/bevy_ecs/src/schedule/mod.rs
index a6d41240e96f4..8f0e6edf2c906 100644
--- a/crates/bevy_ecs/src/schedule/mod.rs
+++ b/crates/bevy_ecs/src/schedule/mod.rs
@@ -37,7 +37,7 @@ use bevy_utils::HashMap;
 /// In this way, the properties of the child schedule can be set differently from the parent.
 /// For example, it can be set to run only once during app execution, while the parent schedule
 /// runs indefinitely.
-#[derive(Default)]
+#[derive(Debug, Default)]
 pub struct Schedule {
     stages: HashMap<StageLabelId, Box<dyn Stage>>,
     stage_order: Vec<StageLabelId>,
diff --git a/crates/bevy_ecs/src/schedule/run_criteria.rs b/crates/bevy_ecs/src/schedule/run_criteria.rs
index 575a63080d3fc..3a4da3351cfcd 100644
--- a/crates/bevy_ecs/src/schedule/run_criteria.rs
+++ b/crates/bevy_ecs/src/schedule/run_criteria.rs
@@ -1,8 +1,10 @@
 use crate::{
+    prelude::System,
     schedule::{GraphNode, RunCriteriaLabel, RunCriteriaLabelId},
     system::{BoxedSystem, IntoSystem, Local},
     world::World,
 };
+use core::fmt::Debug;
 use std::borrow::Cow;
 
 /// Determines whether a system should be executed or not, and how many times it should be ran each
@@ -66,7 +68,19 @@ impl From<bool> for ShouldRun {
     }
 }
 
-#[derive(Default)]
+impl Debug for dyn System<In = (), Out = ShouldRun> + 'static {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "System with In=(), Out=ShouldRun")
+    }
+}
+
+impl Debug for dyn System<In = ShouldRun, Out = ShouldRun> + 'static {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "System with In=ShouldRun, Out=ShouldRun")
+    }
+}
+
+#[derive(Debug, Default)]
 pub(crate) struct BoxedRunCriteria {
     criteria_system: Option<BoxedSystem<(), ShouldRun>>,
     initialized: bool,
@@ -93,6 +107,7 @@ impl BoxedRunCriteria {
     }
 }
 
+#[derive(Debug)]
 pub(crate) enum RunCriteriaInner {
     Single(BoxedSystem<(), ShouldRun>),
     Piped {
@@ -101,6 +116,7 @@ pub(crate) enum RunCriteriaInner {
     },
 }
 
+#[derive(Debug)]
 pub(crate) struct RunCriteriaContainer {
     pub(crate) should_run: ShouldRun,
     pub(crate) inner: RunCriteriaInner,
@@ -165,17 +181,19 @@ impl GraphNode for RunCriteriaContainer {
     }
 }
 
+#[derive(Debug)]
 pub enum RunCriteriaDescriptorOrLabel {
     Descriptor(RunCriteriaDescriptor),
     Label(RunCriteriaLabelId),
 }
 
-#[derive(Clone, Copy)]
+#[derive(Debug, Clone, Copy)]
 pub(crate) enum DuplicateLabelStrategy {
     Panic,
     Discard,
 }
 
+#[derive(Debug)]
 pub struct RunCriteriaDescriptor {
     pub(crate) system: RunCriteriaSystem,
     pub(crate) label: Option<RunCriteriaLabelId>,
@@ -184,6 +202,7 @@ pub struct RunCriteriaDescriptor {
     pub(crate) after: Vec<RunCriteriaLabelId>,
 }
 
+#[derive(Debug)]
 pub(crate) enum RunCriteriaSystem {
     Single(BoxedSystem<(), ShouldRun>),
     Piped(BoxedSystem<ShouldRun, ShouldRun>),
@@ -326,6 +345,7 @@ where
     }
 }
 
+#[derive(Debug)]
 pub struct RunCriteria {
     label: RunCriteriaLabelId,
 }
diff --git a/crates/bevy_ecs/src/schedule/stage.rs b/crates/bevy_ecs/src/schedule/stage.rs
index ff9479c715c37..86bf21407e1d4 100644
--- a/crates/bevy_ecs/src/schedule/stage.rs
+++ b/crates/bevy_ecs/src/schedule/stage.rs
@@ -14,6 +14,7 @@ use crate::{
 };
 use bevy_ecs_macros::Resource;
 use bevy_utils::{tracing::warn, HashMap, HashSet};
+use core::fmt::Debug;
 use downcast_rs::{impl_downcast, Downcast};
 
 use super::IntoSystemDescriptor;
@@ -25,6 +26,12 @@ pub trait Stage: Downcast + Send + Sync {
     fn run(&mut self, world: &mut World);
 }
 
+impl Debug for dyn Stage {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Stage {:?}", self.as_any().downcast_ref::<SystemStage>())
+    }
+}
+
 impl_downcast!(Stage);
 
 /// When this resource is present in the `App`'s `Resources`,
@@ -51,6 +58,7 @@ pub struct ReportExecutionOrderAmbiguities;
 
 /// Stores and executes systems. Execution order is not defined unless explicitly specified;
 /// see `SystemDescriptor` documentation.
+#[derive(Debug)]
 pub struct SystemStage {
     /// The WorldId this stage was last run on.
     world_id: Option<WorldId>,
diff --git a/crates/bevy_ecs/src/schedule/system_container.rs b/crates/bevy_ecs/src/schedule/system_container.rs
index 721faa80f8ac8..8b9cc4d3ccd33 100644
--- a/crates/bevy_ecs/src/schedule/system_container.rs
+++ b/crates/bevy_ecs/src/schedule/system_container.rs
@@ -4,6 +4,7 @@ use crate::{
     schedule::{GraphNode, RunCriteriaLabelId, SystemDescriptor, SystemLabelId},
     system::System,
 };
+use core::fmt::Debug;
 use std::borrow::Cow;
 
 pub struct SystemContainer {
@@ -79,6 +80,12 @@ impl SystemContainer {
     }
 }
 
+impl Debug for SystemContainer {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "\n{{{:?}}}", &self.system())
+    }
+}
+
 impl GraphNode for SystemContainer {
     type Label = SystemLabelId;
 
diff --git a/crates/bevy_ecs/src/schedule/system_descriptor.rs b/crates/bevy_ecs/src/schedule/system_descriptor.rs
index e673f12cc58ab..f61bb44071eeb 100644
--- a/crates/bevy_ecs/src/schedule/system_descriptor.rs
+++ b/crates/bevy_ecs/src/schedule/system_descriptor.rs
@@ -31,6 +31,7 @@ use crate::{
 ///     .with_system(do_the_other_thing.after(Something))
 ///     .with_system(do_something_else.at_end());
 /// ```
+#[derive(Debug)]
 pub struct SystemDescriptor {
     pub(crate) system: BoxedSystem<(), ()>,
     pub(crate) exclusive_insertion_point: Option<ExclusiveInsertionPoint>,
diff --git a/crates/bevy_ecs/src/system/system.rs b/crates/bevy_ecs/src/system/system.rs
index 354d4aa1b0dd7..2b84594cf9077 100644
--- a/crates/bevy_ecs/src/system/system.rs
+++ b/crates/bevy_ecs/src/system/system.rs
@@ -1,4 +1,5 @@
 use bevy_utils::tracing::warn;
+use core::fmt::Debug;
 
 use crate::{
     archetype::ArchetypeComponentId, change_detection::MAX_CHANGE_AGE, component::ComponentId,
@@ -95,3 +96,21 @@ pub(crate) fn check_system_change_tick(
         *last_change_tick = change_tick.wrapping_sub(MAX_CHANGE_AGE);
     }
 }
+
+impl Debug for dyn System<In = (), Out = ()> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{} {{{}}}", self.name(), {
+            if self.is_send() {
+                if self.is_exclusive() {
+                    "is_send is_exclusive"
+                } else {
+                    "is_send"
+                }
+            } else if self.is_exclusive() {
+                "is_exclusive"
+            } else {
+                ""
+            }
+        },)
+    }
+}

From 483d7c3fd0ebca0b954c5471f85caf9b239a3e14 Mon Sep 17 00:00:00 2001
From: targrub <targrub@gmail.com>
Date: Sun, 9 Oct 2022 17:46:53 -0400
Subject: [PATCH 2/8] Added Debug trait to Query, QueryState

---
 crates/bevy_ecs/src/query/state.rs  | 6 ++++++
 crates/bevy_ecs/src/system/query.rs | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/crates/bevy_ecs/src/query/state.rs b/crates/bevy_ecs/src/query/state.rs
index 262e0bcd9fa0c..5e31119d46e99 100644
--- a/crates/bevy_ecs/src/query/state.rs
+++ b/crates/bevy_ecs/src/query/state.rs
@@ -35,6 +35,12 @@ pub struct QueryState<Q: WorldQuery, F: ReadOnlyWorldQuery = ()> {
     pub(crate) filter_state: F::State,
 }
 
+impl<Q: WorldQuery, F: ReadOnlyWorldQuery> std::fmt::Debug for QueryState<Q, F> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "QueryState<Q, F> matched_table_ids: {} matched_archetype_ids: {}", self.matched_table_ids.len(), self.matched_archetype_ids.len())
+    }
+}
+
 impl<Q: WorldQuery, F: ReadOnlyWorldQuery> FromWorld for QueryState<Q, F> {
     fn from_world(world: &mut World) -> Self {
         world.query_filtered()
diff --git a/crates/bevy_ecs/src/system/query.rs b/crates/bevy_ecs/src/system/query.rs
index ce6cc2e470151..43542e0f114a7 100644
--- a/crates/bevy_ecs/src/system/query.rs
+++ b/crates/bevy_ecs/src/system/query.rs
@@ -280,6 +280,12 @@ pub struct Query<'world, 'state, Q: WorldQuery, F: ReadOnlyWorldQuery = ()> {
     pub(crate) change_tick: u32,
 }
 
+impl<'w, 's, Q: WorldQuery, F: ReadOnlyWorldQuery> std::fmt::Debug for Query<'w, 's, Q, F> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Query {{ matched entities: {}, world: {:?}, state: {:?}, last_change_tick: {}, change_tick: {} }}", self.iter().count(), self.world, self.state, self.last_change_tick, self.change_tick)
+    }
+}
+
 impl<'w, 's, Q: WorldQuery, F: ReadOnlyWorldQuery> Query<'w, 's, Q, F> {
     /// Creates a new query.
     ///

From 22feb57d51834694c656501510d3a6445b05058c Mon Sep 17 00:00:00 2001
From: targrub <targrub@gmail.com>
Date: Sun, 9 Oct 2022 18:08:58 -0400
Subject: [PATCH 3/8] Revert some changes to simplify the overall changes

---
 crates/bevy_app/src/app.rs       |  6 +++---
 crates/bevy_ecs/src/archetype.rs | 11 ++---------
 2 files changed, 5 insertions(+), 12 deletions(-)

diff --git a/crates/bevy_app/src/app.rs b/crates/bevy_app/src/app.rs
index 79388fba23902..1b20746072bad 100644
--- a/crates/bevy_app/src/app.rs
+++ b/crates/bevy_app/src/app.rs
@@ -12,7 +12,7 @@ use bevy_ecs::{
     world::World,
 };
 use bevy_utils::{tracing::debug, HashMap};
-use core::fmt::Debug;
+use std::fmt::Debug;
 
 #[cfg(feature = "trace")]
 use bevy_utils::tracing::info_span;
@@ -25,7 +25,7 @@ bevy_utils::define_label!(
 
 /// The [`Resource`] that stores the [`App`]'s [`TypeRegistry`](bevy_reflect::TypeRegistry).
 #[cfg(feature = "bevy_reflect")]
-#[derive(Debug, Resource, Clone, Deref, DerefMut, Default)]
+#[derive(Resource, Clone, Deref, DerefMut, Default)]
 pub struct AppTypeRegistry(pub bevy_reflect::TypeRegistryArc);
 
 #[allow(clippy::needless_doctest_main)]
@@ -72,7 +72,7 @@ pub struct App {
 
 impl Debug for App {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "App {{sub_apps: ")?;
+        write!(f, "App {{ sub_apps: ")?;
         f.debug_map()
             .entries(self.sub_apps.iter().map(|(k, v)| (k, v)))
             .finish()?;
diff --git a/crates/bevy_ecs/src/archetype.rs b/crates/bevy_ecs/src/archetype.rs
index 358ae8099f96e..cf81b5b633a2e 100644
--- a/crates/bevy_ecs/src/archetype.rs
+++ b/crates/bevy_ecs/src/archetype.rs
@@ -32,13 +32,11 @@ impl ArchetypeId {
     }
 }
 
-#[derive(Debug)]
 pub(crate) enum ComponentStatus {
     Added,
     Mutated,
 }
 
-#[derive(Debug)]
 pub struct AddBundle {
     pub archetype_id: ArchetypeId,
     pub(crate) bundle_status: Vec<ComponentStatus>,
@@ -58,7 +56,7 @@ pub struct AddBundle {
 /// yet.
 ///
 /// [`World`]: crate::world::World
-#[derive(Debug, Default)]
+#[derive(Default)]
 pub struct Edges {
     add_bundle: SparseArray<BundleId, AddBundle>,
     remove_bundle: SparseArray<BundleId, Option<ArchetypeId>>,
@@ -120,25 +118,21 @@ impl Edges {
     }
 }
 
-#[derive(Debug)]
 struct TableInfo {
     id: TableId,
     entity_rows: Vec<usize>,
 }
 
-#[derive(Debug)]
 pub(crate) struct ArchetypeSwapRemoveResult {
     pub(crate) swapped_entity: Option<Entity>,
     pub(crate) table_row: usize,
 }
 
-#[derive(Debug)]
 pub(crate) struct ArchetypeComponentInfo {
     pub(crate) storage_type: StorageType,
     pub(crate) archetype_component_id: ArchetypeComponentId,
 }
 
-#[derive(Debug)]
 pub struct Archetype {
     id: ArchetypeId,
     entities: Vec<Entity>,
@@ -352,7 +346,7 @@ impl ArchetypeGeneration {
     }
 }
 
-#[derive(Debug, Hash, PartialEq, Eq)]
+#[derive(Hash, PartialEq, Eq)]
 pub struct ArchetypeIdentity {
     table_components: Box<[ComponentId]>,
     sparse_set_components: Box<[ComponentId]>,
@@ -384,7 +378,6 @@ impl SparseSetIndex for ArchetypeComponentId {
     }
 }
 
-#[derive(Debug)]
 pub struct Archetypes {
     pub(crate) archetypes: Vec<Archetype>,
     pub(crate) archetype_component_count: usize,

From 76adb7ca15e1b91c78e8cf92dee27dc68940bfce Mon Sep 17 00:00:00 2001
From: targrub <targrub@gmail.com>
Date: Sun, 9 Oct 2022 18:22:38 -0400
Subject: [PATCH 4/8] Formatting change.

---
 crates/bevy_ecs/src/query/state.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/crates/bevy_ecs/src/query/state.rs b/crates/bevy_ecs/src/query/state.rs
index 5e31119d46e99..80326b586ca46 100644
--- a/crates/bevy_ecs/src/query/state.rs
+++ b/crates/bevy_ecs/src/query/state.rs
@@ -37,7 +37,12 @@ pub struct QueryState<Q: WorldQuery, F: ReadOnlyWorldQuery = ()> {
 
 impl<Q: WorldQuery, F: ReadOnlyWorldQuery> std::fmt::Debug for QueryState<Q, F> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "QueryState<Q, F> matched_table_ids: {} matched_archetype_ids: {}", self.matched_table_ids.len(), self.matched_archetype_ids.len())
+        write!(
+            f,
+            "QueryState<Q, F> matched_table_ids: {} matched_archetype_ids: {}",
+            self.matched_table_ids.len(),
+            self.matched_archetype_ids.len()
+        )
     }
 }
 

From ec35a1e688dc04a1882690ef4976baa64b5e7530 Mon Sep 17 00:00:00 2001
From: targrub <targrub@gmail.com>
Date: Sun, 9 Oct 2022 21:01:51 -0400
Subject: [PATCH 5/8] Debug adjustments.

Added a copy of the Debug of App for SubApps.
 Removed newline in SystemContainer Debug.  Added more Debug info for Systems with run criteria.
---
 crates/bevy_app/src/app.rs                    |  6 +-
 crates/bevy_ecs/src/schedule/run_criteria.rs  | 58 +++++++++++++++----
 .../bevy_ecs/src/schedule/system_container.rs |  2 +-
 crates/bevy_ecs/src/system/system.rs          |  2 +-
 4 files changed, 53 insertions(+), 15 deletions(-)

diff --git a/crates/bevy_app/src/app.rs b/crates/bevy_app/src/app.rs
index 1b20746072bad..25c2271365544 100644
--- a/crates/bevy_app/src/app.rs
+++ b/crates/bevy_app/src/app.rs
@@ -88,7 +88,11 @@ struct SubApp {
 
 impl Debug for SubApp {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "SubApp")
+        write!(f, "SubApp {{ app: ")?;
+        f.debug_map()
+            .entries(self.app.sub_apps.iter().map(|(k, v)| (k, v)))
+            .finish()?;
+        write!(f, "}}")
     }
 }
 
diff --git a/crates/bevy_ecs/src/schedule/run_criteria.rs b/crates/bevy_ecs/src/schedule/run_criteria.rs
index 3a4da3351cfcd..8bfd84bf04c22 100644
--- a/crates/bevy_ecs/src/schedule/run_criteria.rs
+++ b/crates/bevy_ecs/src/schedule/run_criteria.rs
@@ -68,18 +68,6 @@ impl From<bool> for ShouldRun {
     }
 }
 
-impl Debug for dyn System<In = (), Out = ShouldRun> + 'static {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "System with In=(), Out=ShouldRun")
-    }
-}
-
-impl Debug for dyn System<In = ShouldRun, Out = ShouldRun> + 'static {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "System with In=ShouldRun, Out=ShouldRun")
-    }
-}
-
 #[derive(Debug, Default)]
 pub(crate) struct BoxedRunCriteria {
     criteria_system: Option<BoxedSystem<(), ShouldRun>>,
@@ -366,3 +354,49 @@ impl RunCriteria {
         }
     }
 }
+
+impl Debug for dyn System<In = (), Out = ShouldRun> + 'static {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "System {} with In=(), Out=ShouldRun: {{{}}}",
+            self.name(),
+            {
+                if self.is_send() {
+                    if self.is_exclusive() {
+                        "is_send is_exclusive"
+                    } else {
+                        "is_send"
+                    }
+                } else if self.is_exclusive() {
+                    "is_exclusive"
+                } else {
+                    ""
+                }
+            },
+        )
+    }
+}
+
+impl Debug for dyn System<In = ShouldRun, Out = ShouldRun> + 'static {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "System {} with In=ShouldRun, Out=ShouldRun: {{{}}}",
+            self.name(),
+            {
+                if self.is_send() {
+                    if self.is_exclusive() {
+                        "is_send is_exclusive"
+                    } else {
+                        "is_send"
+                    }
+                } else if self.is_exclusive() {
+                    "is_exclusive"
+                } else {
+                    ""
+                }
+            },
+        )
+    }
+}
diff --git a/crates/bevy_ecs/src/schedule/system_container.rs b/crates/bevy_ecs/src/schedule/system_container.rs
index 8b9cc4d3ccd33..f2c6ad967b79e 100644
--- a/crates/bevy_ecs/src/schedule/system_container.rs
+++ b/crates/bevy_ecs/src/schedule/system_container.rs
@@ -82,7 +82,7 @@ impl SystemContainer {
 
 impl Debug for SystemContainer {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "\n{{{:?}}}", &self.system())
+        write!(f, "{{{:?}}}", &self.system())
     }
 }
 
diff --git a/crates/bevy_ecs/src/system/system.rs b/crates/bevy_ecs/src/system/system.rs
index 2b84594cf9077..43fcdb41dd3cb 100644
--- a/crates/bevy_ecs/src/system/system.rs
+++ b/crates/bevy_ecs/src/system/system.rs
@@ -99,7 +99,7 @@ pub(crate) fn check_system_change_tick(
 
 impl Debug for dyn System<In = (), Out = ()> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{} {{{}}}", self.name(), {
+        write!(f, "System {}: {{{}}}", self.name(), {
             if self.is_send() {
                 if self.is_exclusive() {
                     "is_send is_exclusive"

From 96f7bcc3e43945d2b7638bc1288bf6ba174cc766 Mon Sep 17 00:00:00 2001
From: targrub <targrub@gmail.com>
Date: Sun, 9 Oct 2022 22:00:34 -0400
Subject: [PATCH 6/8] Custom Debug for SystemStage writing Systems on new lines
 if multiple.

---
 crates/bevy_ecs/src/schedule/stage.rs | 59 ++++++++++++++++++++++++++-
 1 file changed, 58 insertions(+), 1 deletion(-)

diff --git a/crates/bevy_ecs/src/schedule/stage.rs b/crates/bevy_ecs/src/schedule/stage.rs
index 86bf21407e1d4..cdea7079f98c5 100644
--- a/crates/bevy_ecs/src/schedule/stage.rs
+++ b/crates/bevy_ecs/src/schedule/stage.rs
@@ -58,7 +58,6 @@ pub struct ReportExecutionOrderAmbiguities;
 
 /// Stores and executes systems. Execution order is not defined unless explicitly specified;
 /// see `SystemDescriptor` documentation.
-#[derive(Debug)]
 pub struct SystemStage {
     /// The WorldId this stage was last run on.
     world_id: Option<WorldId>,
@@ -592,6 +591,64 @@ impl SystemStage {
         }
         Ok(labels)
     }
+
+    pub fn vec_system_container_debug(
+        &self,
+        name: &str,
+        v: &Vec<SystemContainer>,
+        f: &mut std::fmt::Formatter<'_>,
+    ) -> std::fmt::Result {
+        write!(f, "{}: ", name)?;
+        if v.len() > 1 {
+            writeln!(f, "[")?;
+            for sc in v.iter() {
+                writeln!(f, "{:?},", sc)?;
+            }
+            write!(f, "], ")
+        } else {
+            write!(f, "{:?}, ", v)
+        }
+    }
+}
+
+impl std::fmt::Debug for SystemStage {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "SystemStage: {{ ")?;
+        write!(
+            f,
+            "world_id: {:?}, executor: {:?}, stage_run_criteria: {:?}, run_criteria: {:?}, ",
+            self.world_id, self.executor, self.stage_run_criteria, self.run_criteria
+        )?;
+        self.vec_system_container_debug("exclusive_at_start", &self.exclusive_at_start, f)?;
+        self.vec_system_container_debug(
+            "exclusive_before_commands",
+            &self.exclusive_before_commands,
+            f,
+        )?;
+        self.vec_system_container_debug("exclusive_at_end", &self.exclusive_at_end, f)?;
+        self.vec_system_container_debug("parallel", &self.parallel, f)?;
+        write!(
+            f,
+            "systems_modified: {:?}, uninitialized_run_criteria: {:?}, ",
+            self.systems_modified, self.uninitialized_run_criteria
+        )?;
+        write!(
+            f,
+            "uninitialized_at_start: {:?}, uninitialized_before_commands: {:?}, ",
+            self.uninitialized_at_start, self.uninitialized_before_commands
+        )?;
+        write!(
+            f,
+            "uninitialized_at_end: {:?}, uninitialized_parallel: {:?}, ",
+            self.uninitialized_at_end, self.uninitialized_parallel
+        )?;
+        write!(
+            f,
+            "last_tick_check: {:?}, apply_buffers: {:?}, ",
+            self.last_tick_check, self.apply_buffers
+        )?;
+        write!(f, "must_read_resource: {:?}}}", self.must_read_resource)
+    }
 }
 
 /// Sorts given system containers topologically, populates their resolved dependencies

From b319293f3ded265b6c965c13c93d92fa3fb11477 Mon Sep 17 00:00:00 2001
From: targrub <targrub@gmail.com>
Date: Mon, 10 Oct 2022 08:16:59 -0400
Subject: [PATCH 7/8] Handle downcasting of dyn Stage properly.

---
 crates/bevy_ecs/src/schedule/stage.rs | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/crates/bevy_ecs/src/schedule/stage.rs b/crates/bevy_ecs/src/schedule/stage.rs
index cdea7079f98c5..bb14e63e05057 100644
--- a/crates/bevy_ecs/src/schedule/stage.rs
+++ b/crates/bevy_ecs/src/schedule/stage.rs
@@ -17,7 +17,7 @@ use bevy_utils::{tracing::warn, HashMap, HashSet};
 use core::fmt::Debug;
 use downcast_rs::{impl_downcast, Downcast};
 
-use super::IntoSystemDescriptor;
+use super::{IntoSystemDescriptor, Schedule};
 
 /// A type that can run as a step of a [`Schedule`](super::Schedule).
 pub trait Stage: Downcast + Send + Sync {
@@ -28,7 +28,13 @@ pub trait Stage: Downcast + Send + Sync {
 
 impl Debug for dyn Stage {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "Stage {:?}", self.as_any().downcast_ref::<SystemStage>())
+        if let Some(as_systemstage) = self.as_any().downcast_ref::<SystemStage>() {
+            write!(f, "{:?}", as_systemstage)
+        } else if let Some(as_schedule) = self.as_any().downcast_ref::<Schedule>() {
+            write!(f, "{:?}", as_schedule)
+        } else {
+            write!(f, "Unknown dyn Stage")
+        }
     }
 }
 

From 0aa4438b9202829c4e197c3c0996ec02c288ed33 Mon Sep 17 00:00:00 2001
From: targrub <targrub@gmail.com>
Date: Mon, 10 Oct 2022 16:33:52 -0400
Subject: [PATCH 8/8] Added Debug for new enum AmbiguityDetection.

---
 crates/bevy_ecs/src/schedule/system_descriptor.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crates/bevy_ecs/src/schedule/system_descriptor.rs b/crates/bevy_ecs/src/schedule/system_descriptor.rs
index 0e6b37f568ec5..8628069e9042a 100644
--- a/crates/bevy_ecs/src/schedule/system_descriptor.rs
+++ b/crates/bevy_ecs/src/schedule/system_descriptor.rs
@@ -4,7 +4,7 @@ use crate::{
 };
 
 /// Configures ambiguity detection for a single system.
-#[derive(Default)]
+#[derive(Debug, Default)]
 pub(crate) enum AmbiguityDetection {
     #[default]
     Check,