Add SystemGraph as a handle-based method for explicitly creating system dependency graphs

Cargo.toml

@@ -320,6 +320,10 @@ path = "examples/ecs/state.rs"
 name = "system_chaining"
 path = "examples/ecs/system_chaining.rs"
 
+[[example]]
+name = "system_graph"
+path = "examples/ecs/system_graph.rs"
+
 [[example]]
 name = "system_param"
 path = "examples/ecs/system_param.rs"

crates/bevy_app/src/app.rs

@@ -331,7 +331,7 @@ impl App {
     ///         .with_system(system_c),
     /// );
     /// ```
-    pub fn add_system_set(&mut self, system_set: SystemSet) -> &mut Self {
+    pub fn add_system_set(&mut self, system_set: impl Into<SystemSet>) -> &mut Self {
         self.add_system_set_to_stage(CoreStage::Update, system_set)
     }
 
@@ -381,7 +381,7 @@ impl App {
     pub fn add_system_set_to_stage(
         &mut self,
         stage_label: impl StageLabel,
-        system_set: SystemSet,
+        system_set: impl Into<SystemSet>,
     ) -> &mut Self {
         self.schedule
             .add_system_set_to_stage(stage_label, system_set);
@@ -491,7 +491,7 @@ impl App {
     pub fn add_startup_system_set_to_stage(
         &mut self,
         stage_label: impl StageLabel,
-        system_set: SystemSet,
+        system_set: impl Into<SystemSet>,
     ) -> &mut Self {
         self.schedule
             .stage(CoreStage::Startup, |schedule: &mut Schedule| {

crates/bevy_ecs/macros/src/lib.rs

@@ -47,9 +47,9 @@ impl Parse for AllTuples {
 #[proc_macro]
 pub fn all_tuples(input: TokenStream) -> TokenStream {
     let input = parse_macro_input!(input as AllTuples);
-    let len = (input.start..=input.end).count();
+    let len = input.end + 1;
     let mut ident_tuples = Vec::with_capacity(len);
-    for i in input.start..=input.end {
+    for i in 0..=input.end {
         let idents = input
             .idents
             .iter()

crates/bevy_ecs/src/lib.rs

@@ -30,7 +30,8 @@ pub mod prelude {
         schedule::{
             AmbiguitySetLabel, ExclusiveSystemDescriptorCoercion, ParallelSystemDescriptorCoercion,
             RunCriteria, RunCriteriaDescriptorCoercion, RunCriteriaLabel, RunCriteriaPiping,
-            Schedule, Stage, StageLabel, State, SystemLabel, SystemSet, SystemStage,
+            Schedule, Stage, StageLabel, State, SystemGraph, SystemGroup, SystemJoin, SystemLabel,
+            SystemSet, SystemStage,
         },
         system::{
             Commands, ConfigurableSystem, In, IntoChainSystem, IntoExclusiveSystem, IntoSystem,

crates/bevy_ecs/src/schedule/mod.rs

@@ -12,6 +12,7 @@ mod stage;
 mod state;
 mod system_container;
 mod system_descriptor;
+mod system_graph;
 mod system_set;
 
 pub use executor::*;
@@ -23,6 +24,7 @@ pub use stage::*;
 pub use state::*;
 pub use system_container::*;
 pub use system_descriptor::*;
+pub use system_graph::*;
 pub use system_set::*;
 
 use std::fmt::Debug;
@@ -245,7 +247,7 @@ impl Schedule {
     pub fn add_system_set_to_stage(
         &mut self,
         stage_label: impl StageLabel,
-        system_set: SystemSet,
+        system_set: impl Into<SystemSet>,
     ) -> &mut Self {
         self.stage(stage_label, |stage: &mut SystemStage| {
             stage.add_system_set(system_set)

crates/bevy_ecs/src/schedule/stage.rs

@@ -251,12 +251,13 @@ impl SystemStage {
         &self.exclusive_before_commands
     }
 
-    pub fn with_system_set(mut self, system_set: SystemSet) -> Self {
+    pub fn with_system_set(mut self, system_set: impl Into<SystemSet>) -> Self {
         self.add_system_set(system_set);
         self
     }
 
-    pub fn add_system_set(&mut self, system_set: SystemSet) -> &mut Self {
+    pub fn add_system_set(&mut self, system_set: impl Into<SystemSet>) -> &mut Self {
+        let system_set = system_set.into();
         self.systems_modified = true;
         let (run_criteria, mut systems) = system_set.bake();
         let set_run_criteria_index = run_criteria.and_then(|criteria| {