Add Debug implementation for AndroidLogger to facilitate use with log4rs

Cargo.toml

@@ -15,6 +15,10 @@ edition = "2021"
 [features]
 default = ["regex"]
 regex = ["env_filter/regex"]
+log4rs = ["derivative"]
+
+[dependencies]
+derivative = { version = "2.2.0", optional = true }
 
 [dependencies.log]
 version = "0.4"
@@ -25,3 +29,6 @@ version = "0.3"
 [dependencies.env_filter]
 version = "0.1"
 default-features = false
+
+[dev-dependencies]
+log4rs = "1.3.0"

src/lib.rs

@@ -77,6 +77,9 @@ use std::sync::OnceLock;
 
 pub use env_filter::{Builder as FilterBuilder, Filter};
 
+#[cfg(feature = "log4rs")]
+use derivative::Derivative;
+
 pub(crate) type FormatFn = Box<dyn Fn(&mut dyn fmt::Write, &Record) -> fmt::Result + Sync + Send>;
 
 /// Possible identifiers of a specific buffer of Android logging system for
@@ -160,7 +163,10 @@ fn android_log(
 fn android_log(_buf_id: Option<LogId>, _priority: Level, _tag: &CStr, _msg: &CStr) {}
 
 /// Underlying android logger backend
+#[cfg_attr(feature = "log4rs", derive(Derivative))]
+#[cfg_attr(feature = "log4rs", derivative(Debug))]
 pub struct AndroidLogger {
+    #[cfg_attr(feature = "log4rs", derivative(Debug = "ignore"))]
     config: OnceLock<Config>,
 }
 

tests/log4rs.rs

@@ -0,0 +1,52 @@
+#![cfg(feature = "log4rs")]
+
+use android_logger::AndroidLogger;
+use log::{debug, error, info, trace, warn, LevelFilter};
+use std::sync::OnceLock;
+
+#[test]
+fn test_log4rs() {
+    use android_logger::Config as AndroidConfig;
+    use log4rs::append::console::ConsoleAppender;
+    use log4rs::config::{Appender, Root};
+    use log4rs::encode::pattern::PatternEncoder;
+    use log4rs::Config;
+
+    static ANDROID_LOGGER: OnceLock<AndroidLogger> = OnceLock::new();
+    let android_logger = ANDROID_LOGGER.get_or_init(|| {
+        AndroidLogger::new(AndroidConfig::default().with_max_level(LevelFilter::Trace))
+    });
+    let stdout = ConsoleAppender::builder()
+        .encoder(Box::new(PatternEncoder::new("{m}{n}")))
+        .build();
+    match Config::builder()
+        .appender(Appender::builder().build("stdout", Box::new(stdout)))
+        .appender(Appender::builder().build("android_logger", Box::new(android_logger)))
+        .build(
+            Root::builder()
+                .appender("stdout")
+                .appender("android_logger")
+                .build(LevelFilter::Debug),
+        ) {
+        Ok(config) => {
+            let handle = log4rs::init_config(config);
+            if let Err(e) = handle {
+                println!("ERROR: failed to configure logging for stdout with {e:?}");
+            }
+        }
+        Err(e) => {
+            println!("ERROR: failed to prepare default logging configuration with {e:?}");
+        }
+    }
+    // This will not be logged to the Console because of its category's custom level filter.
+    info!(target: "Settings", "Info");
+
+    warn!(target: "Settings", "Warn");
+    error!(target: "Settings", "Error");
+
+    trace!("Trace");
+    debug!("Debug");
+    info!("Info");
+    warn!(target: "Database", "Warn");
+    error!("Error");
+}