use a zero-sized GlobalLogger

Signed-off-by: tison <[email protected]>

Author: tisonkun

src/lib.rs

@@ -1204,7 +1204,7 @@ pub trait Log: Sync + Send {
     fn flush(&self);
 }
 
-// Just used as a dummy initial value for LOGGER
+/// A dummy initial value for LOGGER.
 struct NopLogger;
 
 impl Log for NopLogger {
@@ -1216,6 +1216,28 @@ impl Log for NopLogger {
     fn flush(&self) {}
 }
 
+/// The global logger proxy.
+///
+/// This zero-sized type implements the [`Log`] trait by forwarding calls
+/// to the logger registered with the `set_boxed_logger` or `set_logger`
+/// methods if there is one, or a nop logger as default.
+#[derive(Copy, Clone, Default, Debug)]
+pub struct GlobalLogger;
+
+impl Log for GlobalLogger {
+    fn enabled(&self, metadata: &Metadata) -> bool {
+        logger().enabled(metadata)
+    }
+
+    fn log(&self, record: &Record) {
+        logger().log(record)
+    }
+
+    fn flush(&self) {
+        logger().flush()
+    }
+}
+
 impl<T> Log for &'_ T
 where
     T: ?Sized + Log,

src/macros.rs

@@ -67,7 +67,7 @@ macro_rules! log {
 
     // log!(target: "my_target", Level::Info, "a log event")
     (target: $target:expr, $lvl:expr, $($arg:tt)+) => ({
-        $crate::log!(logger: $crate::logger(), target: $target, $lvl, $($arg)+)
+        $crate::log!(logger: $crate::GlobalLogger, target: $target, $lvl, $($arg)+)
     });
 
     // log!(Level::Info, "a log event")
@@ -318,7 +318,7 @@ macro_rules! log_enabled {
     });
 
     (target: $target:expr, $lvl:expr) => ({
-        $crate::log_enabled!(logger: $crate::logger(), target: $target, $lvl)
+        $crate::log_enabled!(logger: $crate::GlobalLogger, target: $target, $lvl)
     });
 
     ($lvl:expr) => ({