add repro for #1563

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

tracing-subscriber/tests/layer_filters/main.rs

@@ -3,6 +3,7 @@
 mod support;
 use self::support::*;
 mod filter_scopes;
+mod targets;
 mod trees;
 
 use tracing::{level_filters::LevelFilter, Level};

tracing-subscriber/tests/layer_filters/targets.rs

@@ -0,0 +1,42 @@
+use super::*;
+
+use log::*;
+use std::str::FromStr;
+use tracing_subscriber::{
+    filter::{filter_fn, Targets},
+    prelude::*,
+};
+
+#[test]
+fn default_debug() -> Result<(), std::io::Error> {
+    // Reproduces https://github.com/tokio-rs/tracing/issues/1563
+
+    mod inner {
+        use super::*;
+
+        #[tracing::instrument]
+        pub fn events(yak: u32) {
+            debug!("inner - yak: {} - this is debug", yak);
+            info!("inner - yak: {} - this is info", yak);
+            warn!("inner - yak: {} - this is warn", yak);
+        }
+    }
+
+    let filter = Targets::from_str("debug,layer_filters::targets::inner=warn").unwrap();
+
+    let fmt_layer =
+        tracing_subscriber::layer::Identity::new().with_filter(filter_fn(move |_meta| true));
+
+    tracing_subscriber::registry()
+        .with(filter)
+        .with(fmt_layer)
+        .init();
+
+    debug!("before inner");
+
+    inner::events(11111);
+
+    debug!("after inner");
+
+    Ok(())
+}