Log dependency warnings/errors at trace level

Fixes alacritty#5387.

alacritty/src/logging.rs

@@ -13,7 +13,7 @@ use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
 
 use glutin::event_loop::EventLoopProxy;
-use log::{self, Level};
+use log::{self, Level, LevelFilter};
 
 use crate::cli::Options;
 use crate::event::Event;
@@ -102,8 +102,8 @@ impl log::Log for Logger {
         let index = record.target().find(':').unwrap_or_else(|| record.target().len());
         let target = &record.target()[..index];
 
-        // Only log our own crates.
-        if !self.enabled(record.metadata()) || !ALLOWED_TARGETS.contains(&target) {
+        // Only log our own crates, except when logging at Level::Trace.
+        if !self.enabled(record.metadata()) || !is_allowed_target(record.level(), target) {
             return;
         }
 
@@ -149,6 +149,14 @@ fn create_log_message(record: &log::Record<'_>, target: &str) -> String {
     message
 }
 
+/// Check if log messages from a crate should be logged.
+fn is_allowed_target(level: Level, target: &str) -> bool {
+    match (level, log::max_level()) {
+        (Level::Error, LevelFilter::Trace) | (Level::Warn, LevelFilter::Trace) => true,
+        _ => ALLOWED_TARGETS.contains(&target),
+    }
+}
+
 struct OnDemandLogFile {
     file: Option<LineWriter<File>>,
     created: Arc<AtomicBool>,