[Merged by Bors] - [Fixes #6224] Add logging variants of system piping

crates/bevy_ecs/src/system/system_piping.rs

@@ -168,6 +168,7 @@ where
 pub mod adapter {
     use crate::system::In;
     use std::fmt::Debug;
+    use bevy_utils::tracing;
 
     /// Converts a regular function into a system adapter.
     ///
@@ -232,6 +233,54 @@ pub mod adapter {
         res.unwrap()
     }
 
+    /// System adapter that utilizes the [`info!`] macro to print system information.
+    /// 
+    /// # Examples
+    /// 
+    /// ```
+    /// 
+    /// ```
+    pub fn info<T: Debug>(In(data): In<T>) {
+        tracing::info!("{:?}", data);
+    }
+
+    /// System adapter that utilizes the [`warn!`] macro to print the output of a system.
+    ///
+    /// # Examples
+    /// 
+    /// ```
+    /// 
+    /// ```
+    pub fn dbg<T: Debug>(In(data): In<T>) {
+        tracing::debug!("{:?}", data);
+    }
+
+    /// System adapter that utilizes the [`warn!`] macro to print the output of a system.
+    /// 
+    /// # Examples
+    /// 
+    /// ```
+    /// 
+    /// ```
+    pub fn warn<T: Debug>(In(res): In<Option<T>>) {
+        if let Some(warn) = res {
+            tracing::warn!("{:?}", warn);
+        }
+    }
+
+    /// System adapter that utilizes the [`error!`] macro to print the output of a system.
+    /// 
+    /// # Examples
+    /// 
+    /// ```
+    /// 
+    /// ```
+    pub fn error<T, E: Debug>(In(res): In<Result<T, E>>) {
+        if let Err(error) = res {
+            tracing::error!("{:?}", error);
+        }
+    }
+
     /// System adapter that ignores the output of the previous system in a pipe.
     /// This is useful for fallible systems that should simply return early in case of an `Err`/`None`.
     ///

examples/ecs/system_piping.rs

@@ -4,17 +4,33 @@
 use anyhow::Result;
 use bevy::prelude::*;
 
+use bevy::utils::tracing::Level;
+use bevy::log::LogPlugin;
+
 fn main() {
     App::new()
         .insert_resource(Message("42".to_string()))
+        .insert_resource(OptionalWarning(Some("Got to rusty?".to_string())))
+        .add_plugin(LogPlugin {
+            level: Level::TRACE,
+            filter: "".to_string(),
+        })
         .add_system(parse_message_system.pipe(handler_system))
+        .add_system(data_pipe_system.pipe(system_adapter::info))
+        .add_system(parse_message_system.pipe(system_adapter::dbg))
+        .add_system(warning_pipe_system.pipe(system_adapter::warn))
+        .add_system(parse_message_system.pipe(system_adapter::error))
+        .add_system(parse_message_system.pipe(system_adapter::ignore))
         .run();
 }
 
 #[derive(Resource, Deref)]
 struct Message(String);
 
-// this system produces a Result<usize> output by trying to parse the Message resource
+#[derive(Resource, Deref)]
+struct OptionalWarning(Option<String>);
+
+// This system produces a Result<usize> output by trying to parse the Message resource.
 fn parse_message_system(message: Res<Message>) -> Result<usize> {
     Ok(message.parse::<usize>()?)
 }
@@ -28,3 +44,15 @@ fn handler_system(In(result): In<Result<usize>>) {
         Err(err) => println!("encountered an error: {err:?}"),
     }
 }
+
+// This system produces a String output by trying to clone the String from the Message resource.
+fn data_pipe_system(message: Res<Message>) -> String {
+    message.0.clone()
+}
+
+// This system produces an Option<String> output by trying to extract Some(String) from the 
+// OptionalWarning resource. Try changing the OptionalWarning resource to None. You should 
+// not see the warning message printed.
+fn warning_pipe_system(message: Res<OptionalWarning>) -> Option<String> {
+    Some(message.0.to_owned()?)
+}