refactor: layouts and encoders should be nested to appenders

README.md

@@ -44,8 +44,7 @@ fn main() {
     Logger::new().dispatch(
         Dispatch::new()
             .filter(LevelFilter::Trace)
-            .layout(TextLayout::default())
-            .append(append::Stdout),
+            .append(append::Stdout::default()),
         )
         .apply()
         .unwrap();

examples/env_filter.rs

@@ -14,7 +14,6 @@
 
 use logforth::append;
 use logforth::filter::EnvFilter;
-use logforth::layout::TextLayout;
 use logforth::Dispatch;
 use logforth::Logger;
 
@@ -23,8 +22,7 @@ fn main() {
         .dispatch(
             Dispatch::new()
                 .filter(EnvFilter::from_default_env())
-                .layout(TextLayout::default())
-                .append(append::Stdout),
+                .append(append::Stdout::default()),
         )
         .apply()
         .unwrap();

examples/fn_layout_filter.rs

@@ -31,10 +31,11 @@ fn main() {
                         FilterResult::Reject
                     }
                 }))
-                .layout(CustomLayout::new(|record, f| {
-                    f(format_args!("[system alert] {}", record.args()))
-                }))
-                .append(append::Stdout),
+                .append(
+                    append::Stdout::default().with_layout(CustomLayout::new(|record| {
+                        Ok(format!("[system alert] {}", record.args()).into_bytes())
+                    })),
+                ),
         )
         .apply()
         .unwrap();

examples/json_stdio.rs

@@ -23,8 +23,7 @@ fn main() {
         .dispatch(
             Dispatch::new()
                 .filter(LevelFilter::Trace)
-                .layout(JsonLayout::default())
-                .append(append::Stdout),
+                .append(append::Stdout::default().with_layout(JsonLayout::default())),
         )
         .apply()
         .unwrap();

examples/rolling_file.rs

@@ -19,7 +19,6 @@ use logforth::append::rolling_file::RollingFileWriter;
 use logforth::append::rolling_file::Rotation;
 use logforth::append::Stdout;
 use logforth::layout::JsonLayout;
-use logforth::layout::TextLayout;
 use logforth::Dispatch;
 use logforth::Logger;
 
@@ -38,10 +37,9 @@ fn main() {
         .dispatch(
             Dispatch::new()
                 .filter(LevelFilter::Trace)
-                .layout(JsonLayout::default())
-                .append(RollingFile::new(writer)),
+                .append(RollingFile::new(writer).with_layout(JsonLayout::default()))
+                .append(Stdout::default()),
         )
-        .dispatch(Dispatch::new().layout(TextLayout::default()).append(Stdout))
         .apply()
         .unwrap();
 

examples/simple_stdio.rs

@@ -14,7 +14,6 @@
 
 use log::LevelFilter;
 use logforth::append;
-use logforth::layout::TextLayout;
 use logforth::Dispatch;
 use logforth::Logger;
 
@@ -23,14 +22,8 @@ fn main() {
         .dispatch(
             Dispatch::new()
                 .filter(LevelFilter::Trace)
-                .layout(TextLayout::default())
-                .append(append::Stdout),
-        )
-        .dispatch(
-            Dispatch::new()
-                .filter(LevelFilter::Trace)
-                .layout(TextLayout::default().no_color())
-                .append(append::Stderr),
+                .append(append::Stdout::default())
+                .append(append::Stderr::default()),
         )
         .apply()
         .unwrap();

src/append/fastrace.rs

@@ -22,7 +22,9 @@ use crate::layout::collect_kvs;
 
 /// An appender that adds log records to fastrace as an event associated to the current span.
 #[derive(Default, Debug, Clone)]
-pub struct FastraceEvent;
+pub struct FastraceEvent {
+    _private: (), // suppress structure literal syntax
+}
 
 impl Append for FastraceEvent {
     fn append(&self, record: &Record) -> anyhow::Result<()> {

src/append/mod.rs

@@ -24,8 +24,6 @@ pub use self::opentelemetry::OpentelemetryLog;
 pub use self::rolling_file::RollingFile;
 pub use self::stdio::Stderr;
 pub use self::stdio::Stdout;
-use crate::layout::IdenticalLayout;
-use crate::layout::Layout;
 
 #[cfg(feature = "fastrace")]
 mod fastrace;
@@ -41,10 +39,4 @@ pub trait Append: fmt::Debug + Send + Sync + 'static {
 
     /// Flushes any buffered records.
     fn flush(&self) {}
-
-    /// Default layout to use when [`Dispatch`][crate::logger::Dispatch] does not configure a
-    /// preferred layout.
-    fn default_layout(&self) -> Layout {
-        Layout::Identical(IdenticalLayout)
-    }
 }

src/append/opentelemetry.rs

@@ -30,6 +30,7 @@ use opentelemetry_sdk::logs::LogRecord;
 use opentelemetry_sdk::logs::LoggerProvider;
 
 use crate::append::Append;
+use crate::Layout;
 
 /// The communication protocol to opentelemetry that used when exporting data.
 ///
@@ -52,6 +53,7 @@ pub struct OpentelemetryLogBuilder {
     endpoint: String,
     protocol: Protocol,
     labels: Vec<(Cow<'static, str>, Cow<'static, str>)>,
+    layout: Option<Layout>,
 }
 
 impl OpentelemetryLogBuilder {
@@ -62,6 +64,7 @@ impl OpentelemetryLogBuilder {
             endpoint: otlp_endpoint.into(),
             protocol: Protocol::Grpc,
             labels: vec![],
+            layout: None,
         }
     }
 
@@ -100,13 +103,20 @@ impl OpentelemetryLogBuilder {
         self
     }
 
+    /// Set the layout to use when formatting log records.
+    pub fn layout(mut self, layout: impl Into<Layout>) -> Self {
+        self.layout = Some(layout.into());
+        self
+    }
+
     /// Build the [`OpentelemetryLog`] appender.
     pub fn build(self) -> Result<OpentelemetryLog, opentelemetry::logs::LogError> {
         let OpentelemetryLogBuilder {
             name,
             endpoint,
             protocol,
             labels,
+            layout,
         } = self;
 
         let collector_timeout =
@@ -140,6 +150,7 @@ impl OpentelemetryLogBuilder {
 
         Ok(OpentelemetryLog {
             name,
+            layout,
             library,
             provider,
         })
@@ -150,30 +161,34 @@ impl OpentelemetryLogBuilder {
 #[derive(Debug)]
 pub struct OpentelemetryLog {
     name: String,
+    layout: Option<Layout>,
     library: Arc<InstrumentationLibrary>,
     provider: LoggerProvider,
 }
 
 impl Append for OpentelemetryLog {
-    fn append(&self, log_record: &Record) -> anyhow::Result<()> {
+    fn append(&self, record: &Record) -> anyhow::Result<()> {
         let provider = self.provider.clone();
         let logger = provider.library_logger(self.library.clone());
 
-        let mut record = LogRecord::default();
-        record.observed_timestamp = Some(SystemTime::now());
-        record.severity_number = Some(log_level_to_otel_severity(log_record.level()));
-        record.severity_text = Some(log_record.level().as_str());
-        record.target = Some(log_record.target().to_string().into());
-        record.body = Some(AnyValue::from(log_record.args().to_string()));
-
-        if let Some(module_path) = log_record.module_path() {
-            record.add_attribute("module_path", module_path.to_string());
+        let mut log_record_ = LogRecord::default();
+        log_record_.observed_timestamp = Some(SystemTime::now());
+        log_record_.severity_number = Some(log_level_to_otel_severity(record.level()));
+        log_record_.severity_text = Some(record.level().as_str());
+        log_record_.target = Some(record.target().to_string().into());
+        log_record_.body = Some(AnyValue::Bytes(Box::new(match self.layout.as_ref() {
+            None => record.args().to_string().into_bytes(),
+            Some(layout) => layout.format(record)?,
+        })));
+
+        if let Some(module_path) = record.module_path() {
+            log_record_.add_attribute("module_path", module_path.to_string());
         }
-        if let Some(file) = log_record.file() {
-            record.add_attribute("file", file.to_string());
+        if let Some(file) = record.file() {
+            log_record_.add_attribute("file", file.to_string());
         }
-        if let Some(line) = log_record.line() {
-            record.add_attribute("line", line);
+        if let Some(line) = record.line() {
+            log_record_.add_attribute("line", line);
         }
 
         struct KvExtractor<'a> {
@@ -193,11 +208,11 @@ impl Append for OpentelemetryLog {
         }
 
         let mut extractor = KvExtractor {
-            record: &mut record,
+            record: &mut log_record_,
         };
-        log_record.key_values().visit(&mut extractor).ok();
+        record.key_values().visit(&mut extractor).ok();
 
-        logger.emit(record);
+        logger.emit(log_record_);
         Ok(())
     }
 

src/append/rolling_file/append.rs

@@ -16,23 +16,39 @@ use log::Record;
 
 use crate::append::rolling_file::non_blocking::NonBlocking;
 use crate::append::Append;
+use crate::layout::TextLayout;
+use crate::Layout;
 
 /// An appender that writes log records to a file that rolls over when it reaches a certain date
 /// time.
 #[derive(Debug)]
 pub struct RollingFile {
+    layout: Layout,
     writer: NonBlocking,
 }
 
 impl RollingFile {
+    /// Creates a new `RollingFile` appender that writes log records to the given writer.
+    ///
+    /// This appender by default uses [`TextLayout`] to format log records as bytes.
     pub fn new(writer: NonBlocking) -> Self {
-        Self { writer }
+        Self {
+            layout: TextLayout::default().no_color().into(),
+            writer,
+        }
+    }
+
+    /// Sets the layout used to format log records as bytes.
+    pub fn with_layout(mut self, layout: impl Into<Layout>) -> Self {
+        self.layout = layout.into();
+        self
     }
 }
 
 impl Append for RollingFile {
     fn append(&self, record: &Record) -> anyhow::Result<()> {
-        let bytes = format!("{}\n", record.args()).into_bytes();
+        let mut bytes = self.layout.format(record)?;
+        bytes.push(b'\n');
         self.writer.send(bytes)?;
         Ok(())
     }

src/append/stdio.rs

@@ -15,14 +15,35 @@
 use std::io::Write;
 
 use crate::append::Append;
+use crate::layout::TextLayout;
+use crate::Layout;
 
 /// An appender that prints log records to stdout.
-#[derive(Default, Debug)]
-pub struct Stdout;
+#[derive(Debug)]
+pub struct Stdout {
+    layout: Layout,
+}
+
+impl Default for Stdout {
+    fn default() -> Self {
+        Self {
+            layout: TextLayout::default().into(),
+        }
+    }
+}
+
+impl Stdout {
+    /// Creates a new `Stdout` appender with the given layout.
+    pub fn with_layout(mut self, layout: impl Into<Layout>) -> Self {
+        self.layout = layout.into();
+        self
+    }
+}
 
 impl Append for Stdout {
     fn append(&self, record: &log::Record) -> anyhow::Result<()> {
-        let bytes = format!("{}\n", record.args()).into_bytes();
+        let mut bytes = self.layout.format(record)?;
+        bytes.push(b'\n');
         std::io::stdout().write_all(&bytes)?;
         Ok(())
     }
@@ -33,12 +54,31 @@ impl Append for Stdout {
 }
 
 /// An appender that prints log records to stderr.
-#[derive(Default, Debug)]
-pub struct Stderr;
+#[derive(Debug)]
+pub struct Stderr {
+    layout: Layout,
+}
+
+impl Default for Stderr {
+    fn default() -> Self {
+        Self {
+            layout: TextLayout::default().into(),
+        }
+    }
+}
+
+impl Stderr {
+    /// Creates a new `Stderr` appender with the given layout.
+    pub fn with_layout(mut self, encoder: impl Into<Layout>) -> Self {
+        self.layout = encoder.into();
+        self
+    }
+}
 
 impl Append for Stderr {
     fn append(&self, record: &log::Record) -> anyhow::Result<()> {
-        let bytes = format!("{}\n", record.args()).into_bytes();
+        let mut bytes = self.layout.format(record)?;
+        bytes.push(b'\n');
         std::io::stderr().write_all(&bytes)?;
         Ok(())
     }