Add helper for not pipe

Author: Shatur

crates/bevy_ecs/src/system/system_piping.rs

@@ -199,7 +199,7 @@ where
 pub mod adapter {
     use crate::system::In;
     use bevy_utils::tracing;
-    use std::fmt::Debug;
+    use std::{fmt::Debug, ops::Not};
 
     /// Converts a regular function into a system adapter.
     ///
@@ -406,6 +406,34 @@ pub mod adapter {
     /// ```
     pub fn ignore<T>(In(_): In<T>) {}
 
+    /// System adapter that inverts the output of the previous system in a pipe.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bevy_ecs::prelude::*;
+    /// // Building a new schedule/app...
+    /// let mut sched = Schedule::default();
+    /// sched.add_system(
+    ///         // This system will always run.
+    ///         my_system.run_if(always_false.pipe(system_adapter::negate))
+    ///     )
+    ///     // ...
+    /// #   ;
+    /// # let mut world = World::new();
+    /// # sched.run(&mut world);
+    ///
+    /// // A condition that always returns false.
+    /// fn always_false() -> bool {
+    ///    false
+    /// }
+    ///
+    /// # fn my_system() {}
+    /// ```
+    pub fn negate<T: Not>(In(val): In<T>) -> T {
+        !val
+    }
+
     #[cfg(test)]
     #[test]
     fn assert_systems() {
@@ -423,16 +451,12 @@ pub mod adapter {
             unimplemented!()
         }
 
-        fn not(In(val): In<bool>) -> bool {
-            !val
-        }
-
         assert_is_system(returning::<Result<u32, std::io::Error>>.pipe(unwrap));
         assert_is_system(returning::<Option<()>>.pipe(ignore));
         assert_is_system(returning::<&str>.pipe(new(u64::from_str)).pipe(unwrap));
         assert_is_system(exclusive_in_out::<(), Result<(), std::io::Error>>.pipe(error));
         assert_is_system(returning::<bool>.pipe(exclusive_in_out::<bool, ()>));
 
-        returning::<()>.run_if(returning::<bool>.pipe(not));
+        returning::<()>.run_if(returning::<bool>.pipe(negate));
     }
 }