# Objective This PR is heavily inspired by https://github.com/bevyengine/bevy/pull/7682 It aims to solve the same problem: allowing the user to extend the tracing subscriber with extra layers. (in my case, I'd like to use `use metrics_tracing_context::{MetricsLayer, TracingContextLayer};`) ## Solution I'm proposing a different api where the user has the opportunity to take the existing `subscriber` and apply any transformations on it. --- ## Changelog - Added a `update_subscriber` option on the `LogPlugin` that lets the user modify the `subscriber` (for example to extend it with more tracing `Layers` ## Migration Guide > This section is optional. If there are no breaking changes, you can delete this section. - Added a new field `update_subscriber` in the `LogPlugin` --------- Co-authored-by: Charles Bournhonesque <cbournhonesque@snapchat.com>
		
			
				
	
	
		
			71 lines
		
	
	
		
			2.4 KiB
		
	
	
	
		
			Rust
		
	
	
	
	
	
			
		
		
	
	
			71 lines
		
	
	
		
			2.4 KiB
		
	
	
	
		
			Rust
		
	
	
	
	
	
| //! Illustrates how to make a single system from multiple functions running in sequence,
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| //! passing the output of the first into the input of the next.
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| 
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| use bevy::prelude::*;
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| use std::num::ParseIntError;
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| 
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| use bevy::log::LogPlugin;
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| use bevy::utils::{dbg, error, info, tracing::Level, warn};
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| 
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| fn main() {
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|     App::new()
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|         .insert_resource(Message("42".to_string()))
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|         .insert_resource(OptionalWarning(Err("Got to rusty?".to_string())))
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|         .add_plugins(LogPlugin {
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|             level: Level::TRACE,
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|             filter: "".to_string(),
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|             ..default()
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|         })
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|         .add_systems(
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|             Update,
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|             (
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|                 parse_message_system.pipe(handler_system),
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|                 data_pipe_system.map(info),
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|                 parse_message_system.map(dbg),
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|                 warning_pipe_system.map(warn),
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|                 parse_error_message_system.map(error),
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|                 parse_message_system.map(drop),
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|             ),
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|         )
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|         .run();
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| }
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| 
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| #[derive(Resource, Deref)]
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| struct Message(String);
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| 
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| #[derive(Resource, Deref)]
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| struct OptionalWarning(Result<(), String>);
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| 
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| // This system produces a Result<usize> output by trying to parse the Message resource.
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| fn parse_message_system(message: Res<Message>) -> Result<usize, ParseIntError> {
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|     message.parse::<usize>()
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| }
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| 
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| // This system produces a Result<()> output by trying to parse the Message resource.
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| fn parse_error_message_system(message: Res<Message>) -> Result<(), ParseIntError> {
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|     message.parse::<usize>()?;
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|     Ok(())
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| }
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| 
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| // This system takes a Result<usize> input and either prints the parsed value or the error message
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| // Try changing the Message resource to something that isn't an integer. You should see the error
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| // message printed.
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| fn handler_system(In(result): In<Result<usize, ParseIntError>>) {
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|     match result {
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|         Ok(value) => println!("parsed message: {value}"),
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|         Err(err) => println!("encountered an error: {err:?}"),
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|     }
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| }
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| 
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| // This system produces a String output by trying to clone the String from the Message resource.
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| fn data_pipe_system(message: Res<Message>) -> String {
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|     message.0.clone()
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| }
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| 
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| // This system produces an Result<String> output by trying to extract a String from the
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| // OptionalWarning resource. Try changing the OptionalWarning resource to None. You should
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| // not see the warning message printed.
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| fn warning_pipe_system(message: Res<OptionalWarning>) -> Result<(), String> {
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|     message.0.clone()
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| }
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