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#![cfg_attr(test, deny(warnings))]
#![deny(missing_docs)]
#![doc(html_root_url = "https://docs.rs/pretty_env_logger/0.5.0")]
//! A logger configured via an environment variable which writes to standard
//! error with nice colored output for log levels.
//!
//! ## Example
//!
//! ```
//! extern crate pretty_env_logger;
//! #[macro_use] extern crate log;
//!
//! fn main() {
//! pretty_env_logger::init();
//!
//! trace!("a trace example");
//! debug!("deboogging");
//! info!("such information");
//! warn!("o_O");
//! error!("boom");
//! }
//! ```
//!
//! Run the program with the environment variable `RUST_LOG=trace`.
//!
//! ## Defaults
//!
//! The defaults can be setup by calling `init()` or `try_init()` at the start
//! of the program.
//!
//! ## Enable logging
//!
//! This crate uses [env_logger][] internally, so the same ways of enabling
//! logs through an environment variable are supported.
//!
//! [env_logger]: https://docs.rs/env_logger
#[doc(hidden)]
pub extern crate env_logger;
extern crate log;
use std::fmt;
use std::sync::atomic::{AtomicUsize, Ordering};
use env_logger::{
fmt::{Color, Style, StyledValue},
Builder,
};
use log::Level;
/// Initializes the global logger with a pretty env logger.
///
/// This should be called early in the execution of a Rust program, and the
/// global logger may only be initialized once. Future initialization attempts
/// will return an error.
///
/// # Panics
///
/// This function fails to set the global logger if one has already been set.
pub fn init() {
try_init().unwrap();
}
/// Initializes the global logger with a timed pretty env logger.
///
/// This should be called early in the execution of a Rust program, and the
/// global logger may only be initialized once. Future initialization attempts
/// will return an error.
///
/// # Panics
///
/// This function fails to set the global logger if one has already been set.
pub fn init_timed() {
try_init_timed().unwrap();
}
/// Initializes the global logger with a pretty env logger.
///
/// This should be called early in the execution of a Rust program, and the
/// global logger may only be initialized once. Future initialization attempts
/// will return an error.
///
/// # Errors
///
/// This function fails to set the global logger if one has already been set.
pub fn try_init() -> Result<(), log::SetLoggerError> {
try_init_custom_env("RUST_LOG")
}
/// Initializes the global logger with a timed pretty env logger.
///
/// This should be called early in the execution of a Rust program, and the
/// global logger may only be initialized once. Future initialization attempts
/// will return an error.
///
/// # Errors
///
/// This function fails to set the global logger if one has already been set.
pub fn try_init_timed() -> Result<(), log::SetLoggerError> {
try_init_timed_custom_env("RUST_LOG")
}
/// Initialized the global logger with a pretty env logger, with a custom variable name.
///
/// This should be called early in the execution of a Rust program, and the
/// global logger may only be initialized once. Future initialization attempts
/// will return an error.
///
/// # Panics
///
/// This function fails to set the global logger if one has already been set.
pub fn init_custom_env(environment_variable_name: &str) {
try_init_custom_env(environment_variable_name).unwrap();
}
/// Initialized the global logger with a pretty env logger, with a custom variable name.
///
/// This should be called early in the execution of a Rust program, and the
/// global logger may only be initialized once. Future initialization attempts
/// will return an error.
///
/// # Errors
///
/// This function fails to set the global logger if one has already been set.
pub fn try_init_custom_env(environment_variable_name: &str) -> Result<(), log::SetLoggerError> {
let mut builder = formatted_builder();
if let Ok(s) = ::std::env::var(environment_variable_name) {
builder.parse_filters(&s);
}
builder.try_init()
}
/// Initialized the global logger with a timed pretty env logger, with a custom variable name.
///
/// This should be called early in the execution of a Rust program, and the
/// global logger may only be initialized once. Future initialization attempts
/// will return an error.
///
/// # Errors
///
/// This function fails to set the global logger if one has already been set.
pub fn try_init_timed_custom_env(
environment_variable_name: &str,
) -> Result<(), log::SetLoggerError> {
let mut builder = formatted_timed_builder();
if let Ok(s) = ::std::env::var(environment_variable_name) {
builder.parse_filters(&s);
}
builder.try_init()
}
/// Returns a `env_logger::Builder` for further customization.
///
/// This method will return a colored and formatted `env_logger::Builder`
/// for further customization. Refer to env_logger::Build crate documentation
/// for further details and usage.
pub fn formatted_builder() -> Builder {
let mut builder = Builder::new();
builder.format(|f, record| {
use std::io::Write;
let target = record.target();
let max_width = max_target_width(target);
let mut style = f.style();
let level = colored_level(&mut style, record.level());
let mut style = f.style();
let target = style.set_bold(true).value(Padded {
value: target,
width: max_width,
});
writeln!(f, " {} {} > {}", level, target, record.args(),)
});
builder
}
/// Returns a `env_logger::Builder` for further customization.
///
/// This method will return a colored and time formatted `env_logger::Builder`
/// for further customization. Refer to env_logger::Build crate documentation
/// for further details and usage.
pub fn formatted_timed_builder() -> Builder {
let mut builder = Builder::new();
builder.format(|f, record| {
use std::io::Write;
let target = record.target();
let max_width = max_target_width(target);
let mut style = f.style();
let level = colored_level(&mut style, record.level());
let mut style = f.style();
let target = style.set_bold(true).value(Padded {
value: target,
width: max_width,
});
let time = f.timestamp_millis();
writeln!(f, " {} {} {} > {}", time, level, target, record.args(),)
});
builder
}
struct Padded<T> {
value: T,
width: usize,
}
impl<T: fmt::Display> fmt::Display for Padded<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "{: <width$}", self.value, width = self.width)
}
}
static MAX_MODULE_WIDTH: AtomicUsize = AtomicUsize::new(0);
fn max_target_width(target: &str) -> usize {
let max_width = MAX_MODULE_WIDTH.load(Ordering::Relaxed);
if max_width < target.len() {
MAX_MODULE_WIDTH.store(target.len(), Ordering::Relaxed);
target.len()
} else {
max_width
}
}
fn colored_level<'a>(style: &'a mut Style, level: Level) -> StyledValue<'a, &'static str> {
match level {
Level::Trace => style.set_color(Color::Magenta).value("TRACE"),
Level::Debug => style.set_color(Color::Blue).value("DEBUG"),
Level::Info => style.set_color(Color::Green).value("INFO "),
Level::Warn => style.set_color(Color::Yellow).value("WARN "),
Level::Error => style.set_color(Color::Red).value("ERROR"),
}
}