feat: Syslog-adapted formating and auto-detection

Author: djugei

src/fmt/mod.rs

@@ -218,6 +218,7 @@ pub(crate) type FormatFn = Box<dyn RecordFormat + Sync + Send>;
 #[derive(Default)]
 pub(crate) struct Builder {
     pub(crate) format: ConfigurableFormat,
+    pub(crate) format_syslog: bool,
     built: bool,
 }
 
@@ -238,7 +239,25 @@ impl Builder {
             },
         );
 
-        Box::new(built.format)
+        if !built.format_syslog {
+            Box::new(built.format)
+        } else {
+            Box::new(|buf, record| {
+                writeln!(
+                    buf,
+                    "<{}>{}: {}",
+                    match record.level() {
+                        Level::Error => 3,
+                        Level::Warn => 4,
+                        Level::Info => 6,
+                        Level::Debug => 7,
+                        Level::Trace => 7,
+                    },
+                    record.target(),
+                    record.args()
+                )
+            })
+        }
     }
 }
 

src/logger.rs

@@ -160,6 +160,10 @@ impl Builder {
             self.parse_write_style(&s);
         }
 
+        if env.is_daemon() {
+            self.format.format_syslog = true;
+        }
+
         self
     }
 
@@ -299,6 +303,13 @@ impl Builder {
         self
     }
 
+    /// If set to true, format log messages in a Syslog-adapted format.
+    /// Overrides the auto-detected value.
+    pub fn format_syslog(&mut self, syslog: bool) -> &mut Self {
+        self.format.format_syslog = syslog;
+        self
+    }
+
     /// Set the format for structured key/value pairs in the log record
     ///
     /// With the default format, this function is called for each record and should format
@@ -817,6 +828,11 @@ impl<'a> Env<'a> {
     fn get_write_style(&self) -> Option<String> {
         self.write_style.get()
     }
+
+    fn is_daemon(&self) -> bool {
+        //TODO: support more logging systems
+        Var::new("JOURNAL_STREAM").get().is_some()
+    }
 }
 
 impl<'a, T> From<T> for Env<'a>