ded5d523bd
# Objective - Fixes https://github.com/bevyengine/bevy/issues/12597 The current tracing customization option (the `update_subscriber` field) was basically unusable because it provides a `dyn Subscriber` and most layers require a `Subscriber` that also implements `for<'a> LookupSpan<'a, Data=Data<'a>>`, so it was impossible to add a layer on top of the `dyn Subscriber`. This PR provides an alternative way of adding additional tracing layers to the LogPlugin by instead creating an `Option<Layer>`. This is enough for most situations because `Option<Layer>` and `Vec<Layer>` both implement `Layer`. ## Solution - Replace the `update_subscriber` field of `LogPlugin` with a `custom_layer` field which is function pointer returning an `Option<BoxedLayer>` - Update the examples to showcase that this works: - with multiple additional layers - with Layers that were previously problematic, such as `bevy::log::tracing_subscriber::fmt::layer().with_file(true)` (mentioned in the issue) Note that in the example this results in duplicate logs, since we have our own layer on top of the default `fmt_layer` added in the LogPlugin; maybe in the future we might want to provide a single one? Or to let the user customize the default `fmt_layer` ? I still think this change is an improvement upon the previous solution, which was basically broken. --- ## Changelog > This section is optional. If this was a trivial fix, or has no externally-visible impact, you can delete this section. - The `LogPlugin`'s `update_subscriber` field has been replaced with `custom_layer` to allow the user to flexibly add a `tracing::Layer` to the layer stack ## Migration Guide - The `LogPlugin`'s `update_subscriber` field has been replaced with `custom_layer` --------- Co-authored-by: BD103 <59022059+BD103@users.noreply.github.com>
53 lines
1.6 KiB
Rust
53 lines
1.6 KiB
Rust
//! This example illustrates how to add custom log layers in bevy.
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use bevy::log::BoxedLayer;
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use bevy::{log::tracing_subscriber::Layer, prelude::*, utils::tracing::Subscriber};
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struct CustomLayer;
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impl<S: Subscriber> Layer<S> for CustomLayer {
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fn on_event(
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&self,
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event: &bevy::utils::tracing::Event<'_>,
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_ctx: bevy::log::tracing_subscriber::layer::Context<'_, S>,
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) {
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println!("Got event!");
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println!(" level={:?}", event.metadata().level());
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println!(" target={:?}", event.metadata().target());
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println!(" name={:?}", event.metadata().name());
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}
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}
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// We don't need App for this example, as we are just printing log information.
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// For an example that uses App, see log_layers_ecs.
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fn custom_layer(_app: &mut App) -> Option<BoxedLayer> {
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// You can provide multiple layers like this, since Vec<Layer> is also a layer:
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Some(Box::new(vec![
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bevy::log::tracing_subscriber::fmt::layer()
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.with_file(true)
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.boxed(),
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CustomLayer.boxed(),
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]))
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}
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins.set(bevy::log::LogPlugin {
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custom_layer,
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..default()
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}))
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.add_systems(Update, log_system)
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.run();
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}
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fn log_system() {
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// here is how you write new logs at each "log level" (in "most important" to
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// "least important" order)
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error!("something failed");
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warn!("something bad happened that isn't a failure, but thats worth calling out");
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info!("helpful information that is worth printing by default");
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debug!("helpful for debugging");
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trace!("very noisy");
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}
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