From a1a31efcd40995d04e1fa81172441f9953df6c24 Mon Sep 17 00:00:00 2001 From: Gus Wynn Date: Fri, 4 Feb 2022 11:04:30 -0800 Subject: [PATCH] subscriber: add `Targets::would_enable` (#1903 ## Motivation As discussed on discord, this API + `Targets` being `: Clone` makes it easier to solve the original problem I had tried to solve in https://github.com/tokio-rs/tracing/pull/1889. My plan on how to use this is in https://github.com/MaterializeInc/materialize/issues/10441 if you are interested! ## Solution I considered doing some macro magic to create a `Metadata` with a callsite and empty fields and everything, to be able to called `DirectiveSet::enabled`, but it felt cleaner and easier to reason about the special-case-ness (`Targets` never having field filters) using a new set of methods that do a similar thing. For testing I opted for just a doc-test, let me know if thats fine! --- tracing-subscriber/src/filter/targets.rs | 31 +++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) diff --git a/tracing-subscriber/src/filter/targets.rs b/tracing-subscriber/src/filter/targets.rs index efe1cd8db8..0e34f26ffc 100644 --- a/tracing-subscriber/src/filter/targets.rs +++ b/tracing-subscriber/src/filter/targets.rs @@ -20,7 +20,7 @@ use core::{ slice, str::FromStr, }; -use tracing_core::{Collect, Interest, Metadata}; +use tracing_core::{Collect, Interest, Level, Metadata}; /// A filter that enables or disables spans and events based on their [target] /// and [level]. @@ -313,6 +313,35 @@ impl Targets { Interest::never() } } + + /// Returns whether a [target]-[`Level`] pair would be enabled + /// by this `Targets`. + /// + /// This method can be used with [`module_path!`] from `std` as the target + /// in order to emulate the behavior of the [`tracing::event!`] and [`tracing::span!`] + /// macros. + /// + /// # Examples + /// + /// ``` + /// use tracing_subscriber::filter::{Targets, LevelFilter}; + /// use tracing_core::Level; + /// + /// let filter = Targets::new() + /// .with_target("my_crate", Level::INFO) + /// .with_target("my_crate::interesting_module", Level::DEBUG); + /// + /// assert!(filter.would_enable("my_crate", &Level::INFO)); + /// assert!(!filter.would_enable("my_crate::interesting_module", &Level::TRACE)); + /// ``` + /// + /// [target]: tracing_core::Metadata::target + /// [`module_path!`]: std::module_path! + pub fn would_enable(&self, target: &str, level: &Level) -> bool { + // "Correct" to call because `Targets` only produces `StaticDirective`'s with NO + // fields + self.0.target_enabled(target, level) + } } impl Extend<(T, L)> for Targets