From 1f129640262f4c386ae74bb8d1a78de0b8e8c608 Mon Sep 17 00:00:00 2001
From: Carter Anderson <mcanders1@gmail.com>
Date: Sat, 27 Jun 2020 12:06:12 -0700
Subject: [PATCH] legion: remove foreach system functions

this is a bit sad, but upstream legion's new lifetimes appear to be incompatible with our foreach approach
---
 crates/bevy_core/src/time/timer.rs            |   8 +-
 crates/bevy_legion/legion_core/src/lib.rs     |   2 -
 .../legion_core/src/system_fn_types.rs        | 113 -----------
 .../legion_fn_system_macro/src/lib.rs         | 176 +-----------------
 .../legion_systems/src/system_fn.rs           | 110 +----------
 crates/bevy_render/src/draw.rs                |  10 +-
 .../src/pipeline/render_pipelines.rs          |  21 ++-
 crates/bevy_render/src/shader/shader_defs.rs  |  57 +++---
 crates/bevy_ui/src/widget/label.rs            |  81 ++++----
 examples/2d/sprite_sheet.rs                   |  19 +-
 examples/3d/parenting.rs                      |  10 +-
 examples/3d/spawner.rs                        |  12 +-
 examples/3d/z_sort_debug.rs                   |  10 +-
 examples/ecs/ecs_guide.rs                     |  70 ++++---
 examples/ui/font_atlas_debug.rs               |  22 ++-
 examples/ui/text.rs                           |  19 +-
 examples/ui/ui_bench.rs                       |  12 +-
 17 files changed, 215 insertions(+), 537 deletions(-)
 delete mode 100644 crates/bevy_legion/legion_core/src/system_fn_types.rs

diff --git a/crates/bevy_core/src/time/timer.rs b/crates/bevy_core/src/time/timer.rs
index 845bbfc60c..8b4226264a 100644
--- a/crates/bevy_core/src/time/timer.rs
+++ b/crates/bevy_core/src/time/timer.rs
@@ -1,6 +1,6 @@
 use crate::time::Time;
 use bevy_property::Properties;
-use legion::prelude::{ComMut, Res};
+use legion::prelude::{Query, Res, SubWorld, Write};
 use std::time::Duration;
 
 #[derive(Clone, Debug, Default, Properties)]
@@ -37,6 +37,8 @@ impl Timer {
     }
 }
 
-pub fn timer_system(time: Res<Time>, mut timer: ComMut<Timer>) {
-    timer.tick(time.delta_seconds);
+pub fn timer_system(time: Res<Time>, world: &mut SubWorld, query: &mut Query<Write<Timer>>) {
+    for mut timer in query.iter_mut(world) {
+        timer.tick(time.delta_seconds);
+    }
 }
diff --git a/crates/bevy_legion/legion_core/src/lib.rs b/crates/bevy_legion/legion_core/src/lib.rs
index 8670ce0052..4ba09dce61 100644
--- a/crates/bevy_legion/legion_core/src/lib.rs
+++ b/crates/bevy_legion/legion_core/src/lib.rs
@@ -17,13 +17,11 @@ pub mod world;
 #[cfg(feature = "serialize")]
 pub mod serialize;
 
-mod system_fn_types;
 mod tuple;
 mod zip;
 
 pub mod prelude {
     pub use crate::{
-        borrow::{Ref as Com, RefMut as ComMut},
         command::CommandBuffer,
         entity::Entity,
         event::Event,
diff --git a/crates/bevy_legion/legion_core/src/system_fn_types.rs b/crates/bevy_legion/legion_core/src/system_fn_types.rs
deleted file mode 100644
index 4ebff7aff7..0000000000
--- a/crates/bevy_legion/legion_core/src/system_fn_types.rs
+++ /dev/null
@@ -1,113 +0,0 @@
-use crate::{
-    borrow::{Ref, RefIter, RefIterMut, RefMut},
-    filter::{ComponentFilter, EntityFilterTuple, Passthrough},
-    index::{ChunkIndex, SetIndex},
-    query::{DefaultFilter, View, ViewElement},
-    storage::{ArchetypeData, Component, ComponentStorage, ComponentTypeId},
-};
-use std::{
-    any::TypeId,
-    slice::{Iter, IterMut},
-};
-
-impl<'a, T: Component> DefaultFilter for RefMut<'static, T> {
-    type Filter = EntityFilterTuple<ComponentFilter<T>, Passthrough, Passthrough>;
-
-    fn filter() -> Self::Filter { super::filter::filter_fns::component() }
-}
-
-impl<'a, T: Component> View<'a> for RefMut<'static, T> {
-    type Iter = RefIterMut<'a, T, IterMut<'a, T>>;
-
-    #[inline]
-    fn fetch(
-        _: &'a ArchetypeData,
-        chunk: &'a ComponentStorage,
-        _: ChunkIndex,
-        _: SetIndex,
-    ) -> Self::Iter {
-        let (slice_borrow, slice) = unsafe {
-            chunk
-                .components(ComponentTypeId::of::<T>())
-                .unwrap_or_else(|| {
-                    panic!(
-                        "Component of type {:?} not found in chunk when fetching Write view",
-                        std::any::type_name::<T>()
-                    )
-                })
-                .data_slice_mut::<T>()
-                .deconstruct()
-        };
-        RefIterMut::new(slice_borrow, slice.iter_mut())
-    }
-
-    #[inline]
-    fn validate() -> bool { true }
-
-    #[inline]
-    fn reads<D: Component>() -> bool { TypeId::of::<T>() == TypeId::of::<D>() }
-
-    #[inline]
-    fn writes<D: Component>() -> bool { TypeId::of::<T>() == TypeId::of::<D>() }
-
-    #[inline]
-    fn read_types() -> Vec<ComponentTypeId> { vec![ComponentTypeId::of::<T>()] }
-
-    #[inline]
-    fn write_types() -> Vec<ComponentTypeId> { vec![ComponentTypeId::of::<T>()] }
-}
-
-impl<'a, T: Component> ViewElement for RefMut<'static, T> {
-    type Component = T;
-}
-
-impl<'a, T: Component> DefaultFilter for Ref<'static, T> {
-    type Filter = EntityFilterTuple<ComponentFilter<T>, Passthrough, Passthrough>;
-
-    fn filter() -> Self::Filter { super::filter::filter_fns::component() }
-}
-
-impl<'a, T: Component> View<'a> for Ref<'static, T> {
-    type Iter = RefIter<'a, T, Iter<'a, T>>;
-
-    #[inline]
-    fn fetch(
-        _: &'a ArchetypeData,
-        chunk: &'a ComponentStorage,
-        _: ChunkIndex,
-        _: SetIndex,
-    ) -> Self::Iter {
-        let (slice_borrow, slice) = unsafe {
-            chunk
-                .components(ComponentTypeId::of::<T>())
-                .unwrap_or_else(|| {
-                    panic!(
-                        "Component of type {:?} not found in chunk when fetching Write view",
-                        std::any::type_name::<T>()
-                    )
-                })
-                .data_slice::<T>()
-                .deconstruct()
-        };
-        RefIter::new(slice_borrow, slice.iter())
-    }
-
-    #[inline]
-    fn validate() -> bool { true }
-
-    #[inline]
-    fn reads<D: Component>() -> bool { TypeId::of::<T>() == TypeId::of::<D>() }
-
-    #[inline]
-    fn writes<D: Component>() -> bool { false }
-
-    #[inline]
-    fn read_types() -> Vec<ComponentTypeId> { vec![ComponentTypeId::of::<T>()] }
-
-    #[inline]
-    fn write_types() -> Vec<ComponentTypeId> { Vec::new() }
-}
-
-impl<'a, T: Component> ViewElement for Ref<'static, T> {
-    type Component = T;
-}
diff --git a/crates/bevy_legion/legion_fn_system_macro/src/lib.rs b/crates/bevy_legion/legion_fn_system_macro/src/lib.rs
index 96bd2a6029..dfde2ef4b5 100644
--- a/crates/bevy_legion/legion_fn_system_macro/src/lib.rs
+++ b/crates/bevy_legion/legion_fn_system_macro/src/lib.rs
@@ -21,164 +21,6 @@ fn get_idents(fmt_string: fn(usize) -> String, count: usize) -> Vec<Ident> {
         .collect::<Vec<Ident>>()
 }
 
-#[proc_macro]
-pub fn impl_fn_systems(_input: TokenStream) -> TokenStream {
-    let max_resources = 8;
-    let max_views = 8;
-    let resources = get_idents(|i| format!("R{}", i), max_resources);
-    let resource_vars = get_idents(|i| format!("r{}", i), max_resources);
-    let views = get_idents(|i| format!("V{}", i), max_views);
-    let view_vars = get_idents(|i| format!("v{}", i), max_views);
-
-    let mut tokens = TokenStream::new();
-
-    let command_buffer = vec![Ident::new("CommandBuffer", Span::call_site())];
-    let command_buffer_var = vec![Ident::new("_command_buffer", Span::call_site())];
-    for resource_count in 0..=max_resources {
-        let resource = &resources[0..resource_count];
-        let resource_var = &resource_vars[0..resource_count];
-
-        let resource_tuple = tuple(resource);
-        let resource_var_tuple = tuple(resource_var);
-
-        let resource_access = if resource_count == 0 {
-            quote! { Access::default() }
-        } else {
-            quote! {{
-                let mut resource_access: Access<ResourceTypeId> = Access::default();
-                resource_access
-                    .reads
-                    .extend(<#resource_tuple as ResourceSet>::read_types().iter());
-                resource_access
-                    .writes
-                    .extend(<#resource_tuple as ResourceSet>::write_types().iter());
-                resource_access
-            }}
-        };
-
-        for view_count in 0..=max_views {
-            let view = &views[0..view_count];
-            let view_var = &view_vars[0..view_count];
-
-            let view_tuple = tuple(view);
-
-            let component_access = if view_count == 0 {
-                quote! { Access::default() }
-            } else {
-                quote! {{
-                    let mut component_access: Access<ComponentTypeId> = Access::default();
-                    component_access
-                        .reads
-                        .extend(<#view_tuple as View>::read_types().iter());
-                    component_access
-                        .writes
-                        .extend(<#view_tuple as View>::write_types().iter());
-                    component_access
-                }}
-            };
-
-            let system_query = if view_count == 0 {
-                quote! { () }
-            } else if view_count == 1 {
-                quote! { SystemQuery<
-                    #(#view),*,
-                    #(<#view as DefaultFilter>::Filter),*,
-                > }
-            } else {
-                quote! { SystemQuery<
-                    (#(#view),*),
-                    EntityFilterTuple<
-                        And<(
-                            #(<<#view as DefaultFilter>::Filter as EntityFilter>::ArchetypeFilter),*
-                        )>,
-                        And<(
-                            #(<<#view as DefaultFilter>::Filter as EntityFilter>::ChunksetFilter),*
-                        )>,
-                        And<(
-                            #(<<#view as DefaultFilter>::Filter as EntityFilter>::ChunkFilter),*
-                        )>,
-                    >
-                >   }
-            };
-
-            let query = if view_count == 0 {
-                quote! {()}
-            } else {
-                quote! {<#view_tuple>::query()}
-            };
-
-            for command_buffer_index in 0..2 {
-                let command_buffer = &command_buffer[0..command_buffer_index];
-                let command_buffer_var = &command_buffer_var[0..command_buffer_index];
-
-                let run_fn = if view_count == 0 {
-                    quote! { self(#(#resource_var,)* #(#command_buffer_var,)*) }
-                } else {
-                    quote! {
-                        for (#(#view_var),*) in _query.iter_mut(_world) {
-                            self(#(#resource_var.clone(),)* #(#command_buffer_var,)* #(#view_var),*);
-                        }
-                    }
-                };
-
-                tokens.extend(TokenStream::from(quote! {
-                    impl<'a,
-                        Func,
-                        #(#resource: ResourceSet<PreparedResources = #resource> + 'static + Clone,)*
-                        #(#view: for<'b> View<'b> + DefaultFilter + ViewElement,)*
-                    > IntoSystem<(#(#command_buffer)*), (#(#resource,)*), (#(#view,)*), ()> for Func
-                    where
-                        Func: FnMut(#(#resource,)* #(&mut #command_buffer,)* #(#view),*) + Send + Sync + 'static,
-                        #(<#view as View<'a>>::Iter: Iterator<Item = #view>,
-                        <#view as DefaultFilter>::Filter: Sync),*
-                    {
-                        fn system_id(mut self, id: SystemId) -> Box<dyn Schedulable> {
-                            let resource_access: Access<ResourceTypeId> = #resource_access;
-                            let component_access: Access<ComponentTypeId> = #component_access;
-
-                            let run_fn = FuncSystemFnWrapper(
-                                move |_command_buffer,
-                                    _world,
-                                    _resources: #resource_tuple,
-                                    _query: &mut #system_query
-                                | {
-                                    let #resource_var_tuple = _resources;
-                                    #run_fn
-                                },
-                                PhantomData,
-                            );
-
-                            Box::new(FuncSystem {
-                                name: id,
-                                queries: AtomicRefCell::new(#query),
-                                access: SystemAccess {
-                                    resources: resource_access,
-                                    components: component_access,
-                                    tags: Access::default(),
-                                },
-                                archetypes: ArchetypeAccess::Some(BitSet::default()),
-                                _resources: PhantomData::<#resource_tuple>,
-                                command_buffer: FxHashMap::default(),
-                                run_fn: AtomicRefCell::new(run_fn),
-                            })
-                        }
-
-                        fn system_named(self, name: &'static str) -> Box<dyn Schedulable> {
-                            self.system_id(name.into())
-                        }
-
-                        fn system(self) -> Box<dyn Schedulable> {
-                            self.system_id(std::any::type_name::<Self>().to_string().into())
-                        }
-                    }
-                }));
-            }
-        }
-    }
-
-    tokens
-}
-
 #[proc_macro]
 pub fn impl_fn_query_systems(_input: TokenStream) -> TokenStream {
     let max_resources = 8;
@@ -193,6 +35,8 @@ pub fn impl_fn_query_systems(_input: TokenStream) -> TokenStream {
 
     let command_buffer = vec![Ident::new("CommandBuffer", Span::call_site())];
     let command_buffer_var = vec![Ident::new("_command_buffer", Span::call_site())];
+    let subworld = vec![Ident::new("SubWorld", Span::call_site())];
+    let subworld_var = vec![Ident::new("_world", Span::call_site())];
     for resource_count in 0..=max_resources {
         let resource = &resources[0..resource_count];
         let resource_var = &resource_vars[0..resource_count];
@@ -215,12 +59,14 @@ pub fn impl_fn_query_systems(_input: TokenStream) -> TokenStream {
             }}
         };
 
-        for query_count in 1..=max_queries {
+        for query_count in 0..=max_queries {
             let view = &views[0..query_count];
             let query_var = &query_vars[0..query_count];
 
             let view_tuple = tuple(view);
             let query_var_tuple = tuple(query_var);
+            let subworld = &subworld[0..query_count.min(1)];
+            let subworld_var = &subworld_var[0..query_count.min(1)];
 
             let component_access = if query_count == 0 {
                 quote! { Access::default() }
@@ -241,19 +87,13 @@ pub fn impl_fn_query_systems(_input: TokenStream) -> TokenStream {
                 let command_buffer = &command_buffer[0..command_buffer_index];
                 let command_buffer_var = &command_buffer_var[0..command_buffer_index];
 
-                let view_tuple_avoid_type_collision = if query_count == 1 {
-                    quote! {(#(#view)*,)}
-                } else {
-                    quote! {(#(#view,)*)}
-                };
-
                 tokens.extend(TokenStream::from(quote! {
                     impl<Func,
                         #(#resource: ResourceSet<PreparedResources = #resource> + 'static + Clone,)*
                         #(#view: for<'b> View<'b> + DefaultFilter + ViewElement),*
-                    > IntoSystem<(#(#command_buffer)*), (#(#resource,)*), (), #view_tuple_avoid_type_collision> for Func
+                    > IntoSystem<(#(#command_buffer)*), (#(#resource,)*), (#(#view,)*)> for Func
                     where
-                        Func: FnMut(#(#resource,)*#(&mut #command_buffer,)* &mut SubWorld, #(&mut SystemQuery<#view, <#view as DefaultFilter>::Filter>),*) + Send + Sync + 'static,
+                        Func: FnMut(#(#resource,)*#(&mut #command_buffer,)* #(&mut #subworld,)* #(&mut SystemQuery<#view, <#view as DefaultFilter>::Filter>),*) + Send + Sync + 'static,
                         #(<#view as DefaultFilter>::Filter: Sync),*
                     {
                         fn system_id(mut self, id: SystemId) -> Box<dyn Schedulable> {
@@ -268,7 +108,7 @@ pub fn impl_fn_query_systems(_input: TokenStream) -> TokenStream {
                                 | {
                                     let #resource_var_tuple = _resources;
                                     let #query_var_tuple = _queries;
-                                    self(#(#resource_var,)*#(#command_buffer_var,)*_world,#(#query_var),*)
+                                    self(#(#resource_var,)*#(#command_buffer_var,)*#(#subworld_var,)*#(#query_var),*)
                                 },
                                 PhantomData,
                             );
diff --git a/crates/bevy_legion/legion_systems/src/system_fn.rs b/crates/bevy_legion/legion_systems/src/system_fn.rs
index af03e65fc0..f6e9341ced 100644
--- a/crates/bevy_legion/legion_systems/src/system_fn.rs
+++ b/crates/bevy_legion/legion_systems/src/system_fn.rs
@@ -9,20 +9,18 @@ use fxhash::FxHashMap;
 use legion_core::{
     borrow::AtomicRefCell,
     command::CommandBuffer,
-    filter::{And, EntityFilter, EntityFilterTuple},
     query::{DefaultFilter, IntoQuery, View, ViewElement},
     storage::ComponentTypeId,
 };
-use legion_fn_system_macro::{impl_fn_query_systems, impl_fn_systems};
+use legion_fn_system_macro::impl_fn_query_systems;
 use std::marker::PhantomData;
 
-pub trait IntoSystem<CommandBuffer, Resources, Views, Queries> {
+pub trait IntoSystem<CommandBuffer, Resources, Queries> {
     fn system_id(self, id: SystemId) -> Box<dyn Schedulable>;
     fn system_named(self, name: &'static str) -> Box<dyn Schedulable>;
     fn system(self) -> Box<dyn Schedulable>;
 }
 
-impl_fn_systems!();
 impl_fn_query_systems!();
 
 #[allow(type_alias_bounds)]
@@ -33,14 +31,8 @@ where
 
 #[cfg(test)]
 mod tests {
-    use crate::{
-        resource::Resources,
-        system_fn_types::{Res, ResMut},
-        IntoSystem, Query, SubWorld,
-    };
+    use crate::{resource::Resources, system_fn_types::Res, IntoSystem, Query, SubWorld};
     use legion_core::{
-        borrow::{Ref, RefMut},
-        command::CommandBuffer,
         query::{Read, Write},
         world::World,
     };
@@ -68,10 +60,12 @@ mod tests {
                 println!("{:?}", x);
             }
         }
+        let mut system = query_system.system();
+        system.run(&mut world, &mut resources);
 
         fn query_system2(
-            world: &mut SubWorld,
             a: Res<A>,
+            world: &mut SubWorld,
             query: &mut Query<(Read<X>, Write<Y>)>,
             query2: &mut Query<Read<X>>,
         ) {
@@ -86,98 +80,14 @@ mod tests {
             }
         }
 
-        let mut system = query_system.system();
         let mut system2 = query_system2.system();
-        system.run(&mut world, &mut resources);
         system2.run(&mut world, &mut resources);
-    }
 
-    #[test]
-    fn test_into_system() {
-        let mut world = World::new();
-        let mut resources = Resources::default();
-        resources.insert(A(0));
-        world.insert((), vec![(X(1), Y(1)), (X(2), Y(2))]);
-
-        fn single_read_system(x: Ref<X>) {
-            println!("{}", x.0);
-        }
-        let mut system = single_read_system.system();
-        system.run(&mut world, &mut resources);
-
-        fn read_write_system(x: Ref<X>, y: Ref<Y>, mut z: RefMut<A>) {
-            z.0 += 1;
-            println!("{} {} {}", x.0, y.0, z.0);
+        fn query_system3(a: Res<A>) {
+            println!("{:?}", *a);
         }
 
-        ({
-            |x: Res<A>, y: Ref<Y>, mut z: RefMut<A>| {
-                z.0 += 1;
-                println!("{} {} {}", x.0, y.0, z.0);
-            }
-        })
-        .system();
-
-        let mut system = read_write_system.system();
-        system.run(&mut world, &mut resources);
-
-        fn resource_system(a: Res<A>, x: Ref<X>, y: Ref<Y>) {
-            println!("{} {} {}", a.0, x.0, y.0);
-        }
-
-        let mut system = resource_system.system();
-        system.run(&mut world, &mut resources);
-
-        fn empty_system_mut() {
-            println!("hello world");
-        }
-
-        let mut system = empty_system_mut.system();
-        system.run(&mut world, &mut resources);
-
-        fn resource_system_mut(mut a: ResMut<A>, x: Ref<X>, y: Ref<Y>) {
-            a.0 += 1;
-            println!("{} {} {}", a.0, x.0, y.0);
-        }
-        let mut system = resource_system_mut.system();
-        system.run(&mut world, &mut resources);
-
-        fn command_buffer_system(command_buffer: &mut CommandBuffer, mut a: ResMut<A>) {
-            a.0 += 1;
-            command_buffer.insert((), vec![(X(1), Y(1)), (X(2), Y(2))]);
-            println!("{}", a.0);
-        }
-        let mut system = command_buffer_system.system();
-        system.run(&mut world, &mut resources);
-    }
-
-    #[test]
-    fn test_resource_system_fn() {
-        fn my_system(mut a: ResMut<A>, x: Ref<X>, mut y: RefMut<Y>) {
-            if a.0 == 0 {
-                assert_eq!(*a, A(0));
-                assert_eq!(*x, X(2));
-                assert_eq!(*y, Y(3));
-            } else if a.0 == 1 {
-                assert_eq!(*a, A(1));
-                assert_eq!(*x, X(4));
-                assert_eq!(*y, Y(5));
-                y.0 += 1;
-                assert_eq!(*y, Y(6));
-            } else {
-                panic!("unexpected value");
-            }
-
-            a.0 += 1;
-        }
-
-        let mut world = World::new();
-        let mut resources = Resources::default();
-
-        resources.insert(A(0));
-        resources.insert(B(1));
-        world.insert((), vec![(X(2), Y(3)), (X(4), Y(5))]);
-        let mut my_system = my_system.system();
-        my_system.run(&mut world, &mut resources);
+        let mut system3 = query_system3.system();
+        system3.run(&mut world, &mut resources);
     }
 }
diff --git a/crates/bevy_render/src/draw.rs b/crates/bevy_render/src/draw.rs
index f7bfc39cbb..8d8bc78945 100644
--- a/crates/bevy_render/src/draw.rs
+++ b/crates/bevy_render/src/draw.rs
@@ -13,8 +13,8 @@ use crate::{
 use bevy_asset::{Assets, Handle};
 use bevy_property::Properties;
 use legion::{
-    prelude::{ComMut, Res, ResourceSet},
-    systems::{resource::ResourceTypeId, ResMut},
+    prelude::{Res, ResourceSet, Write},
+    systems::{resource::ResourceTypeId, ResMut, SubWorld, Query},
 };
 use std::{
     ops::{Deref, DerefMut, Range},
@@ -340,6 +340,8 @@ pub trait Drawable {
     fn draw(&mut self, draw: &mut Draw, context: &mut DrawContext) -> Result<(), DrawError>;
 }
 
-pub fn clear_draw_system(mut draw: ComMut<Draw>) {
-    draw.clear_render_commands();
+pub fn clear_draw_system(world: &mut SubWorld, query: &mut Query<Write<Draw>>) {
+    for mut draw in query.iter_mut(world) {
+        draw.clear_render_commands();
+    }
 }
diff --git a/crates/bevy_render/src/pipeline/render_pipelines.rs b/crates/bevy_render/src/pipeline/render_pipelines.rs
index e05addabf9..be0f7497f5 100644
--- a/crates/bevy_render/src/pipeline/render_pipelines.rs
+++ b/crates/bevy_render/src/pipeline/render_pipelines.rs
@@ -5,7 +5,10 @@ use crate::{
 };
 use bevy_asset::Handle;
 use bevy_property::Properties;
-use legion::{prelude::ComMut, systems::ResMut};
+use legion::{
+    prelude::Write,
+    systems::{Query, ResMut, SubWorld},
+};
 #[derive(Properties, Default, Clone)]
 pub struct RenderPipeline {
     pub pipeline: Handle<PipelineDescriptor>,
@@ -104,12 +107,14 @@ impl<'a> Drawable for DrawableRenderPipelines<'a> {
 pub fn draw_render_pipelines_system(
     mut draw_context: DrawContext,
     mut render_resource_bindings: ResMut<RenderResourceBindings>,
-    mut draw: ComMut<Draw>,
-    mut render_pipelines: ComMut<RenderPipelines>,
+    world: &mut SubWorld,
+    query: &mut Query<(Write<Draw>, Write<RenderPipelines>)>,
 ) {
-    let mut drawable = DrawableRenderPipelines {
-        render_pipelines: &mut render_pipelines,
-        render_resource_bindings: &mut render_resource_bindings,
-    };
-    drawable.draw(&mut draw, &mut draw_context).unwrap();
+    for (mut draw, mut render_pipelines) in query.iter_mut(world) {
+        let mut drawable = DrawableRenderPipelines {
+            render_pipelines: &mut render_pipelines,
+            render_resource_bindings: &mut render_resource_bindings,
+        };
+        drawable.draw(&mut draw, &mut draw_context).unwrap();
+    }
 }
diff --git a/crates/bevy_render/src/shader/shader_defs.rs b/crates/bevy_render/src/shader/shader_defs.rs
index 4fb2439246..e5e3c1d4ab 100644
--- a/crates/bevy_render/src/shader/shader_defs.rs
+++ b/crates/bevy_render/src/shader/shader_defs.rs
@@ -1,6 +1,9 @@
 use crate::{texture::Texture, RenderPipelines};
 use bevy_asset::{Assets, Handle};
-use legion::prelude::{Com, ComMut, Res};
+use legion::{
+    prelude::{Read, Res, Write},
+    systems::{Query, SubWorld},
+};
 
 pub use bevy_derive::ShaderDefs;
 
@@ -55,46 +58,52 @@ impl ShaderDef for Option<Handle<Texture>> {
     }
 }
 
-pub fn shader_defs_system<T>(shader_defs: Com<T>, mut render_pipelines: ComMut<RenderPipelines>)
+pub fn shader_defs_system<T>(world: &mut SubWorld, query: Query<(Read<T>, Write<RenderPipelines>)>)
 where
     T: ShaderDefs + Send + Sync + 'static,
 {
-    for shader_def in shader_defs.iter_shader_defs() {
+    for (shader_defs, mut render_pipelines) in query.iter_mut(world) {
+        for shader_def in shader_defs.iter_shader_defs() {
+            for render_pipeline in render_pipelines.pipelines.iter_mut() {
+                render_pipeline
+                    .specialization
+                    .shader_specialization
+                    .shader_defs
+                    .insert(shader_def.to_string());
+            }
+        }
+    }
+}
+
+pub fn clear_shader_defs_system(world: &mut SubWorld, query: &mut Query<Write<RenderPipelines>>) {
+    for mut render_pipelines in query.iter_mut(world) {
         for render_pipeline in render_pipelines.pipelines.iter_mut() {
             render_pipeline
                 .specialization
                 .shader_specialization
                 .shader_defs
-                .insert(shader_def.to_string());
+                .clear();
         }
     }
 }
 
-pub fn clear_shader_defs_system(mut render_pipelines: ComMut<RenderPipelines>) {
-    for render_pipeline in render_pipelines.pipelines.iter_mut() {
-        render_pipeline
-            .specialization
-            .shader_specialization
-            .shader_defs
-            .clear();
-    }
-}
-
 pub fn asset_shader_defs_system<T>(
     assets: Res<Assets<T>>,
-    asset_handle: Com<Handle<T>>,
-    mut render_pipelines: ComMut<RenderPipelines>,
+    world: &mut SubWorld,
+    query: &mut Query<(Read<Handle<T>>, Write<RenderPipelines>)>,
 ) where
     T: ShaderDefs + Send + Sync + 'static,
 {
-    let shader_defs = assets.get(&asset_handle).unwrap();
-    for shader_def in shader_defs.iter_shader_defs() {
-        for render_pipeline in render_pipelines.pipelines.iter_mut() {
-            render_pipeline
-                .specialization
-                .shader_specialization
-                .shader_defs
-                .insert(shader_def.to_string());
+    for (asset_handle, mut render_pipelines) in query.iter_mut(world) {
+        let shader_defs = assets.get(&asset_handle).unwrap();
+        for shader_def in shader_defs.iter_shader_defs() {
+            for render_pipeline in render_pipelines.pipelines.iter_mut() {
+                render_pipeline
+                    .specialization
+                    .shader_specialization
+                    .shader_defs
+                    .insert(shader_def.to_string());
+            }
         }
     }
 }
diff --git a/crates/bevy_ui/src/widget/label.rs b/crates/bevy_ui/src/widget/label.rs
index 1693dc15c7..0e834ffc42 100644
--- a/crates/bevy_ui/src/widget/label.rs
+++ b/crates/bevy_ui/src/widget/label.rs
@@ -6,10 +6,10 @@ use bevy_render::{
     texture::Texture,
     Color,
 };
-use bevy_sprite::{ComMut, TextureAtlas};
+use bevy_sprite::TextureAtlas;
 use bevy_text::{DrawableText, Font, FontAtlasSet, TextStyle};
 use bevy_transform::prelude::Transform;
-use legion::prelude::{Com, Res, ResMut};
+use legion::prelude::*;
 
 pub struct Label {
     pub text: String,
@@ -37,25 +37,28 @@ impl Label {
         fonts: Res<Assets<Font>>,
         mut font_atlas_sets: ResMut<Assets<FontAtlasSet>>,
         mut texture_atlases: ResMut<Assets<TextureAtlas>>,
-        label: Com<Label>,
+        world: &mut SubWorld,
+        query: &mut Query<Read<Label>>,
     ) {
-        let font_atlases = font_atlas_sets
-            .get_or_insert_with(Handle::from_id(label.font.id), || {
-                FontAtlasSet::new(label.font)
-            });
-        // TODO: this call results in one or more TextureAtlases, whose render resources are created in the RENDER_GRAPH_SYSTEMS
-        // stage. That logic runs _before_ the DRAW stage, which means we cant call add_glyphs_to_atlas in the draw stage
-        // without our render resources being a frame behind. Therefore glyph atlasing either needs its own system or the TextureAtlas
-        // resource generation needs to happen AFTER the render graph systems. maybe draw systems should execute within the
-        // render graph so ordering like this can be taken into account? Maybe the RENDER_GRAPH_SYSTEMS stage should be removed entirely
-        // in favor of node.update()? Regardless, in the immediate short term the current approach is fine.
-        font_atlases.add_glyphs_to_atlas(
-            &fonts,
-            &mut texture_atlases,
-            &mut textures,
-            label.style.font_size,
-            &label.text,
-        );
+        for label in query.iter(world) {
+            let font_atlases = font_atlas_sets
+                .get_or_insert_with(Handle::from_id(label.font.id), || {
+                    FontAtlasSet::new(label.font)
+                });
+            // TODO: this call results in one or more TextureAtlases, whose render resources are created in the RENDER_GRAPH_SYSTEMS
+            // stage. That logic runs _before_ the DRAW stage, which means we cant call add_glyphs_to_atlas in the draw stage
+            // without our render resources being a frame behind. Therefore glyph atlasing either needs its own system or the TextureAtlas
+            // resource generation needs to happen AFTER the render graph systems. maybe draw systems should execute within the
+            // render graph so ordering like this can be taken into account? Maybe the RENDER_GRAPH_SYSTEMS stage should be removed entirely
+            // in favor of node.update()? Regardless, in the immediate short term the current approach is fine.
+            font_atlases.add_glyphs_to_atlas(
+                &fonts,
+                &mut texture_atlases,
+                &mut textures,
+                label.style.font_size,
+                &label.text,
+            );
+        }
     }
 
     pub fn draw_label_system(
@@ -65,26 +68,26 @@ impl Label {
         texture_atlases: Res<Assets<TextureAtlas>>,
         mut render_resource_bindings: ResMut<RenderResourceBindings>,
         mut asset_render_resource_bindings: ResMut<AssetRenderResourceBindings>,
-        mut draw: ComMut<Draw>,
-        label: Com<Label>,
-        node: Com<Node>,
-        transform: Com<Transform>,
+        world: &mut SubWorld,
+        query: &mut Query<(Write<Draw>, Read<Label>, Read<Node>, Read<Transform>)>,
     ) {
-        // let position = transform.0 - quad.size / 2.0;
-        let position = transform.value.w_axis().truncate() - (node.size / 2.0).extend(0.0);
+        for (mut draw, label, node, transform) in query.iter_mut(world) {
+            // let position = transform.0 - quad.size / 2.0;
+            let position = transform.value.w_axis().truncate() - (node.size / 2.0).extend(0.0);
 
-        let mut drawable_text = DrawableText::new(
-            fonts.get(&label.font).unwrap(),
-            font_atlas_sets
-                .get(&label.font.as_handle::<FontAtlasSet>())
-                .unwrap(),
-            &texture_atlases,
-            &mut render_resource_bindings,
-            &mut asset_render_resource_bindings,
-            position,
-            &label.style,
-            &label.text,
-        );
-        drawable_text.draw(&mut draw, &mut draw_context).unwrap();
+            let mut drawable_text = DrawableText::new(
+                fonts.get(&label.font).unwrap(),
+                font_atlas_sets
+                    .get(&label.font.as_handle::<FontAtlasSet>())
+                    .unwrap(),
+                &texture_atlases,
+                &mut render_resource_bindings,
+                &mut asset_render_resource_bindings,
+                position,
+                &label.style,
+                &label.text,
+            );
+            drawable_text.draw(&mut draw, &mut draw_context).unwrap();
+        }
     }
 }
diff --git a/examples/2d/sprite_sheet.rs b/examples/2d/sprite_sheet.rs
index ea21749df8..33e92f482d 100644
--- a/examples/2d/sprite_sheet.rs
+++ b/examples/2d/sprite_sheet.rs
@@ -10,14 +10,19 @@ fn main() {
 
 fn animate_sprite_system(
     texture_atlases: Res<Assets<TextureAtlas>>,
-    mut timer: ComMut<Timer>,
-    mut sprite: ComMut<TextureAtlasSprite>,
-    texture_atlas_handle: Com<Handle<TextureAtlas>>,
+    world: &mut SubWorld,
+    query: &mut Query<(
+        Write<Timer>,
+        Write<TextureAtlasSprite>,
+        Read<Handle<TextureAtlas>>,
+    )>,
 ) {
-    if timer.finished {
-        let texture_atlas = texture_atlases.get(&texture_atlas_handle).unwrap();
-        sprite.index = ((sprite.index as usize + 1) % texture_atlas.textures.len()) as u32;
-        timer.reset();
+    for (mut timer, mut sprite, texture_atlas_handle) in query.iter_mut(world) {
+        if timer.finished {
+            let texture_atlas = texture_atlases.get(&texture_atlas_handle).unwrap();
+            sprite.index = ((sprite.index as usize + 1) % texture_atlas.textures.len()) as u32;
+            timer.reset();
+        }
     }
 }
 
diff --git a/examples/3d/parenting.rs b/examples/3d/parenting.rs
index a8039581a6..a2a8a8c034 100644
--- a/examples/3d/parenting.rs
+++ b/examples/3d/parenting.rs
@@ -11,8 +11,14 @@ fn main() {
 }
 
 /// rotates the parent, which will result in the child also rotating
-fn rotator_system(time: Res<Time>, _rotator: ComMut<Rotator>, mut rotation: ComMut<Rotation>) {
-    rotation.0 = rotation.0 * Quat::from_rotation_x(3.0 * time.delta_seconds);
+fn rotator_system(
+    time: Res<Time>,
+    world: &mut SubWorld,
+    query: &mut Query<(Read<Rotator>, Write<Rotation>)>,
+) {
+    for (_rotator, mut rotation) in query.iter_mut(world) {
+        rotation.0 = rotation.0 * Quat::from_rotation_x(3.0 * time.delta_seconds);
+    }
 }
 
 /// set up a simple scene with a "parent" cube and a "child" cube
diff --git a/examples/3d/spawner.rs b/examples/3d/spawner.rs
index bb6749df39..3738167d05 100644
--- a/examples/3d/spawner.rs
+++ b/examples/3d/spawner.rs
@@ -17,12 +17,14 @@ fn main() {
 fn move_cubes(
     time: Res<Time>,
     mut materials: ResMut<Assets<StandardMaterial>>,
-    mut translation: ComMut<Translation>,
-    material_handle: Com<Handle<StandardMaterial>>,
+    world: &mut SubWorld,
+    query: &mut Query<(Write<Translation>, Read<Handle<StandardMaterial>>)>,
 ) {
-    let material = materials.get_mut(&material_handle).unwrap();
-    translation.0 += math::vec3(1.0, 0.0, 0.0) * time.delta_seconds;
-    material.albedo += Color::rgb(-time.delta_seconds, -time.delta_seconds, time.delta_seconds);
+    for (mut translation, material_handle) in query.iter_mut(world) {
+        let material = materials.get_mut(&material_handle).unwrap();
+        translation.0 += math::vec3(1.0, 0.0, 0.0) * time.delta_seconds;
+        material.albedo += Color::rgb(-time.delta_seconds, -time.delta_seconds, time.delta_seconds);
+    }
 }
 
 fn setup(
diff --git a/examples/3d/z_sort_debug.rs b/examples/3d/z_sort_debug.rs
index 9036fce298..a293342971 100644
--- a/examples/3d/z_sort_debug.rs
+++ b/examples/3d/z_sort_debug.rs
@@ -12,8 +12,14 @@ fn main() {
 }
 
 /// rotates the parent, which will result in the child also rotating
-fn rotator_system(time: Res<Time>, _rotator: ComMut<Rotator>, mut rotation: ComMut<Rotation>) {
-    rotation.0 = rotation.0 * Quat::from_rotation_x(3.0 * time.delta_seconds);
+fn rotator_system(
+    time: Res<Time>,
+    world: &mut SubWorld,
+    query: &mut Query<(Read<Rotator>, Write<Rotation>)>,
+) {
+    for (_rotator, mut rotation) in query.iter_mut(world) {
+        rotation.0 = rotation.0 * Quat::from_rotation_x(3.0 * time.delta_seconds);
+    }
 }
 
 fn camera_order_color_system(
diff --git a/examples/ecs/ecs_guide.rs b/examples/ecs/ecs_guide.rs
index 2884f0c427..8f8f2c767a 100644
--- a/examples/ecs/ecs_guide.rs
+++ b/examples/ecs/ecs_guide.rs
@@ -80,21 +80,22 @@ fn new_round_system(game_rules: Res<GameRules>, mut game_state: ResMut<GameState
     );
 }
 
-// This system runs once for each entity with both the "Player" and "Score" component.
-// NOTE: Com<Player> is a read-only component reference, whereas ComMut<Score> can modify the component
-fn score_system(player: Com<Player>, mut score: ComMut<Score>) {
-    let scored_a_point = random::<bool>();
-    if scored_a_point {
-        score.value += 1;
-        println!(
-            "{} scored a point! Their score is: {}",
-            player.name, score.value
-        );
-    } else {
-        println!(
-            "{} did not score a point! Their score is: {}",
-            player.name, score.value
-        );
+// This system updates the score for each entity with the "Player" and "Score" component.
+fn score_system(world: &mut SubWorld, query: &mut Query<(Read<Player>, Write<Score>)>) {
+    for (player, mut score) in query.iter_mut(world) {
+        let scored_a_point = random::<bool>();
+        if scored_a_point {
+            score.value += 1;
+            println!(
+                "{} scored a point! Their score is: {}",
+                player.name, score.value
+            );
+        } else {
+            println!(
+                "{} did not score a point! Their score is: {}",
+                player.name, score.value
+            );
+        }
     }
 
     // this game isn't very fun is it :)
@@ -102,26 +103,11 @@ fn score_system(player: Com<Player>, mut score: ComMut<Score>) {
 
 // This system runs on all entities with the "Player" and "Score" components, but it also
 // accesses the "GameRules" resource to determine if a player has won.
-// NOTE: resources must always come before components in system functions
+// NOTE: resources must always come before worlds/queries in system functions
 fn score_check_system(
     game_rules: Res<GameRules>,
     mut game_state: ResMut<GameState>,
-    player: Com<Player>,
-    score: Com<Score>,
-) {
-    if score.value == game_rules.winning_score {
-        game_state.winning_player = Some(player.name.clone());
-    }
-}
-
-// If you need more control over iteration or direct access to SubWorld, you can also use "query systems"
-// This is how you would represent the system above with a "query system"
-// NOTE: You can add as many queries as you want, but they must come after all resources (Res/ResMut).
-#[allow(dead_code)]
-fn query_score_check_system(
     world: &mut SubWorld,
-    game_rules: Res<GameRules>,
-    mut game_state: ResMut<GameState>,
     query: &mut Query<(Read<Player>, Read<Score>)>,
 ) {
     for (player, score) in query.iter(world) {
@@ -191,7 +177,7 @@ fn startup_system(world: &mut World, resources: &mut Resources) {
 // Normal systems cannot safely access the World instance directly because they run in parallel.
 // Our World contains all of our components, so accessing it in parallel is not thread safe.
 // Command buffers give us the ability to queue up changes to our World without directly accessing it
-// NOTE: Command buffers must always come before resources and components in system functions
+// NOTE: Command buffers must always come after resources and before queries in system functions
 fn new_player_system(
     game_rules: Res<GameRules>,
     mut game_state: ResMut<GameState>,
@@ -252,9 +238,11 @@ fn thread_local_system(world: &mut World, resources: &mut Resources) {
 #[allow(dead_code)]
 fn closure_system() -> Box<dyn Schedulable> {
     let mut counter = 0;
-    (move |player: Com<Player>, score: Com<Score>| {
-        println!("processed: {} {}", player.name, score.value);
-        println!("this ran {} times", counter);
+    (move |world: &mut SubWorld, query: &mut Query<(Read<Player>, Read<Score>)>| {
+        for (player, score) in query.iter(world) {
+            println!("processed: {} {}", player.name, score.value);
+        }
+        println!("this system ran {} times", counter);
         counter += 1;
     })
     .system()
@@ -270,9 +258,15 @@ struct State {
 
 // NOTE: this doesn't do anything relevant to our game, it is just here for illustrative purposes
 #[allow(dead_code)]
-fn stateful_system(mut state: ComMut<State>, player: Com<Player>, score: ComMut<Score>) {
-    println!("processed: {} {}", player.name, score.value);
-    println!("this ran {} times", state.counter);
+fn stateful_system(
+    mut state: ResMut<State>,
+    world: &mut SubWorld,
+    query: &mut Query<(Read<Player>, Read<Score>)>,
+) {
+    for (player, score) in query.iter(world) {
+        println!("processed: {} {}", player.name, score.value);
+    }
+    println!("this system ran {} times", state.counter);
     state.counter += 1;
 }
 
diff --git a/examples/ui/font_atlas_debug.rs b/examples/ui/font_atlas_debug.rs
index e1e1b8de34..11853df11f 100644
--- a/examples/ui/font_atlas_debug.rs
+++ b/examples/ui/font_atlas_debug.rs
@@ -50,11 +50,18 @@ fn atlas_render_system(
     }
 }
 
-fn text_update_system(mut state: ResMut<State>, time: Res<Time>, mut label: ComMut<Label>) {
-    state.timer.tick(time.delta_seconds);
-    if state.timer.finished {
-        label.text = format!("{}", rand::random::<u8>() as char);
-        state.timer.reset();
+fn text_update_system(
+    mut state: ResMut<State>,
+    time: Res<Time>,
+    world: &mut SubWorld,
+    query: &mut Query<Write<Label>>,
+) {
+    for mut label in query.iter_mut(world) {
+        state.timer.tick(time.delta_seconds);
+        if state.timer.finished {
+            label.text = format!("{}", rand::random::<u8>() as char);
+            state.timer.reset();
+        }
     }
 }
 
@@ -71,10 +78,7 @@ fn setup(
         .entity_with(OrthographicCameraComponents::default())
         // texture
         .entity_with(LabelComponents {
-            node: Node::new(
-                Anchors::TOP_LEFT,
-                Margins::new(0.0, 250.0, 0.0, 60.0),
-            ),
+            node: Node::new(Anchors::TOP_LEFT, Margins::new(0.0, 250.0, 0.0, 60.0)),
             label: Label {
                 text: "a".to_string(),
                 font: font_handle,
diff --git a/examples/ui/text.rs b/examples/ui/text.rs
index e9ac10c67e..037c9d18f7 100644
--- a/examples/ui/text.rs
+++ b/examples/ui/text.rs
@@ -12,10 +12,16 @@ fn main() {
         .run();
 }
 
-fn text_update_system(diagnostics: Res<Diagnostics>, mut label: ComMut<Label>) {
-    if let Some(fps) = diagnostics.get(FrameTimeDiagnosticsPlugin::FPS) {
-        if let Some(average) = fps.average() {
-            label.text = format!("FPS: {:.2}", average);
+fn text_update_system(
+    diagnostics: Res<Diagnostics>,
+    world: &mut SubWorld,
+    query: &mut Query<Write<Label>>,
+) {
+    for mut label in query.iter_mut(world) {
+        if let Some(fps) = diagnostics.get(FrameTimeDiagnosticsPlugin::FPS) {
+            if let Some(average) = fps.average() {
+                label.text = format!("FPS: {:.2}", average);
+            }
         }
     }
 }
@@ -28,10 +34,7 @@ fn setup(asset_server: Res<AssetServer>, command_buffer: &mut CommandBuffer) {
         .entity_with(OrthographicCameraComponents::default())
         // texture
         .entity_with(LabelComponents {
-            node: Node::new(
-                Anchors::TOP_LEFT,
-                Margins::new(0.0, 250.0, 0.0, 60.0),
-            ),
+            node: Node::new(Anchors::TOP_LEFT, Margins::new(0.0, 250.0, 0.0, 60.0)),
             label: Label {
                 text: "FPS:".to_string(),
                 font: font_handle,
diff --git a/examples/ui/ui_bench.rs b/examples/ui/ui_bench.rs
index 03d9f3a8f4..7f15642aaf 100644
--- a/examples/ui/ui_bench.rs
+++ b/examples/ui/ui_bench.rs
@@ -12,12 +12,14 @@ fn main() {
 fn placement_system(
     time: Res<Time>,
     materials: Res<Assets<ColorMaterial>>,
-    mut node: ComMut<Node>,
-    material_handle: Com<Handle<ColorMaterial>>,
+    world: &mut SubWorld,
+    query: &mut Query<(Write<Node>, Read<Handle<ColorMaterial>>)>,
 ) {
-    let material = materials.get(&material_handle).unwrap();
-    if material.color.r > 0.2 {
-        node.position += Vec2::new(0.1 * time.delta_seconds, 0.0);
+    for (mut node, material_handle) in query.iter_mut(world) {
+        let material = materials.get(&material_handle).unwrap();
+        if material.color.r > 0.2 {
+            node.position += Vec2::new(0.1 * time.delta_seconds, 0.0);
+        }
     }
 }