log: Logger receiveis a LogRecord

The logging macros now create a LogRecord, and pass that to the
Logger, instead of passing a `level` and `args`. The new signature is:

    trait Logger {
        fn log(&mut self, record: &LogRecord);
    }

The LogRecord includes additional values that may be useful to custom
loggers, and also allows for further expansion if not values are found
useful.

DefaultLogger's formatting was taken from Python's default formatting:
`LEVEL:from: message`

Also included: fmt::Arguments now implement Show, so they can be used to
extend format strings.

[breaking-change]

6 files changed, 92 insertions, 16 deletions

diff --git a/src/liblog/directive.rs b/src/liblog/directive.rs
index 4329f68b9aa..afbcf8c6ded 100644
--- a/src/liblog/directive.rs
+++ b/src/liblog/directive.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use std::ascii::StrAsciiExt;
 use std::cmp;
 
 #[deriving(Show, Clone)]
@@ -16,13 +17,13 @@ pub struct LogDirective {
     pub level: u32,
 }
 
-static LOG_LEVEL_NAMES: [&'static str, ..4] = ["error", "warn", "info",
-                                               "debug"];
+pub static LOG_LEVEL_NAMES: [&'static str, ..4] = ["ERROR", "WARN", "INFO",
+                                               "DEBUG"];
 
 /// Parse an individual log level that is either a number or a symbolic log level
 fn parse_log_level(level: &str) -> Option<u32> {
     from_str::<u32>(level).or_else(|| {
-        let pos = LOG_LEVEL_NAMES.iter().position(|&name| name == level);
+        let pos = LOG_LEVEL_NAMES.iter().position(|&name| name.eq_ignore_ascii_case(level));
         pos.map(|p| p as u32 + 1)
     }).map(|p| cmp::min(p, ::MAX_LOG_LEVEL))
 }
diff --git a/src/liblog/lib.rs b/src/liblog/lib.rs
index 87c82e1dd7d..d0426b1e407 100644
--- a/src/liblog/lib.rs
+++ b/src/liblog/lib.rs
@@ -129,6 +129,8 @@ use std::slice;
 
 use sync::one::{Once, ONCE_INIT};
 
+use directive::LOG_LEVEL_NAMES;
+
 pub mod macros;
 mod directive;
 
@@ -162,19 +164,42 @@ local_data_key!(local_logger: ~Logger:Send)
 /// can have its own custom logger which can respond to logging messages
 /// however it likes.
 pub trait Logger {
-    /// Logs a single message described by the `args` structure. The level is
-    /// provided in case you want to do things like color the message, etc.
-    fn log(&mut self, level: u32, args: &fmt::Arguments);
+    /// Logs a single message described by the `record`.
+    fn log(&mut self, record: &LogRecord);
 }
 
 struct DefaultLogger {
     handle: LineBufferedWriter<io::stdio::StdWriter>,
 }
 
+/// Wraps the log level with fmt implementations.
+#[deriving(Eq, Ord)]
+pub struct LogLevel(pub u32);
+
+impl fmt::Show for LogLevel {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        let LogLevel(level) = *self;
+        match LOG_LEVEL_NAMES.get(level as uint - 1) {
+            Some(name) => name.fmt(fmt),
+            None => level.fmt(fmt)
+        }
+    }
+}
+
+impl fmt::Signed for LogLevel {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        let LogLevel(level) = *self;
+        write!(fmt.buf, "{}", level)
+    }
+}
+
 impl Logger for DefaultLogger {
-    // by default, just ignore the level
-    fn log(&mut self, _level: u32, args: &fmt::Arguments) {
-        match fmt::writeln(&mut self.handle, args) {
+    fn log(&mut self, record: &LogRecord) {
+        match write!(&mut self.handle,
+                     "{}:{}: {}",
+                     record.level,
+                     record.module_path,
+                     record.args) {
             Err(e) => fail!("failed to log: {}", e),
             Ok(()) => {}
         }
@@ -198,14 +223,21 @@ impl Drop for DefaultLogger {
 ///
 /// It is not recommended to call this function directly, rather it should be
 /// invoked through the logging family of macros.
-pub fn log(level: u32, args: &fmt::Arguments) {
+#[doc(hidden)]
+pub fn log(level: u32, loc: &'static LogLocation, args: &fmt::Arguments) {
     // Completely remove the local logger from TLS in case anyone attempts to
     // frob the slot while we're doing the logging. This will destroy any logger
     // set during logging.
     let mut logger = local_data::pop(local_logger).unwrap_or_else(|| {
         ~DefaultLogger { handle: io::stderr() } as ~Logger:Send
     });
-    logger.log(level, args);
+    logger.log(&LogRecord {
+        level: LogLevel(level),
+        args: args,
+        file: loc.file,
+        module_path: loc.module_path,
+        line: loc.line,
+    });
     local_data::set(local_logger, logger);
 }
 
@@ -223,6 +255,34 @@ pub fn set_logger(logger: ~Logger:Send) -> Option<~Logger:Send> {
     return prev;
 }
 
+/// A LogRecord is created by the logging macros, and passed as the only
+/// argument to Loggers.
+#[deriving(Show)]
+pub struct LogRecord<'a> {
+
+    /// The module path of where the LogRecord originated.
+    pub module_path: &'a str,
+
+    /// The LogLevel of this record.
+    pub level: LogLevel,
+
+    /// The arguments from the log line.
+    pub args: &'a fmt::Arguments<'a>,
+
+    /// The file of where the LogRecord originated.
+    pub file: &'a str,
+
+    /// The line number of where the LogRecord originated.
+    pub line: uint,
+}
+
+#[doc(hidden)]
+pub struct LogLocation {
+    pub module_path: &'static str,
+    pub file: &'static str,
+    pub line: uint,
+}
+
 /// Tests whether a given module's name is enabled for a particular level of
 /// logging. This is the second layer of defense about determining whether a
 /// module's log statement should be emitted or not.
diff --git a/src/liblog/macros.rs b/src/liblog/macros.rs
index f1d4a318bf0..3bb49c237f1 100644
--- a/src/liblog/macros.rs
+++ b/src/liblog/macros.rs
@@ -33,9 +33,14 @@
 #[macro_export]
 macro_rules! log(
     ($lvl:expr, $($arg:tt)+) => ({
+        static LOC: ::log::LogLocation = ::log::LogLocation {
+            line: line!(),
+            file: file!(),
+            module_path: module_path!(),
+        };
         let lvl = $lvl;
         if log_enabled!(lvl) {
-            format_args!(|args| { ::log::log(lvl, args) }, $($arg)+)
+            format_args!(|args| { ::log::log(lvl, &LOC, args) }, $($arg)+)
         }
     })
 )
diff --git a/src/libstd/fmt/mod.rs b/src/libstd/fmt/mod.rs
index 8e4d8707cca..e225dc42e05 100644
--- a/src/libstd/fmt/mod.rs
+++ b/src/libstd/fmt/mod.rs
@@ -565,6 +565,12 @@ pub struct Arguments<'a> {
     args: &'a [Argument<'a>],
 }
 
+impl<'a> Show for Arguments<'a> {
+    fn fmt(&self, fmt: &mut Formatter) -> Result {
+        write(fmt.buf, self)
+    }
+}
+
 /// When a format is not otherwise specified, types are formatted by ascribing
 /// to this trait. There is not an explicit way of selecting this trait to be
 /// used for formatting, it is only if no other format is specified.
diff --git a/src/test/run-pass/capturing-logging.rs b/src/test/run-pass/capturing-logging.rs
index a6443dc5a1a..3859ed3a53d 100644
--- a/src/test/run-pass/capturing-logging.rs
+++ b/src/test/run-pass/capturing-logging.rs
@@ -19,14 +19,14 @@ extern crate native;
 
 use std::fmt;
 use std::io::{ChanReader, ChanWriter};
-use log::{set_logger, Logger};
+use log::{set_logger, Logger, LogRecord};
 
 struct MyWriter(ChanWriter);
 
 impl Logger for MyWriter {
-    fn log(&mut self, _level: u32, args: &fmt::Arguments) {
+    fn log(&mut self, record: &LogRecord) {
         let MyWriter(ref mut inner) = *self;
-        fmt::writeln(inner as &mut Writer, args);
+        fmt::writeln(inner as &mut Writer, record.args);
     }
 }
 
diff --git a/src/test/run-pass/ifmt.rs b/src/test/run-pass/ifmt.rs
index d20c4ec8373..16b21f5f537 100644
--- a/src/test/run-pass/ifmt.rs
+++ b/src/test/run-pass/ifmt.rs
@@ -33,7 +33,7 @@ impl fmt::Signed for B {
     }
 }
 
-macro_rules! t(($a:expr, $b:expr) => { assert_eq!($a, $b.to_owned()) })
+macro_rules! t(($a:expr, $b:expr) => { assert_eq!($a.as_slice(), $b) })
 
 pub fn main() {
     // Make sure there's a poly formatter that takes anything
@@ -202,6 +202,10 @@ fn test_format_args() {
 
     let s = format_args!(fmt::format, "hello {}", "world");
     t!(s, "hello world");
+    let s = format_args!(|args| {
+        format!("{}: {}", "args were", args)
+    }, "hello {}", "world");
+    t!(s, "args were: hello world");
 }
 
 fn test_order() {