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colors.rs
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colors.rs
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//! Module containing color-related functions using the `colored` crate.
//!
//! This module is only available when the `colored` feature is enabled for `fern`.
//! This can be done with the following in `Cargo.toml`:
//!
//! ```toml
//! [dependencies]
//! # ...
//! fern = { version = "0.4", features = ["colored"] }
//! ```
use std::fmt;
pub use colored::Color;
use log::LogLevel;
/// Extension crate allowing the use of `.colored` on LogLevels.
trait ColoredLogLevel {
/// Colors this log level with the given color.
fn colored(&self, color: Color) -> WithFgColor<LogLevel>;
}
/// Opaque structure which represents some text data and a color to display it with. This implements [`fmt::Display`]
/// via displaying the inner text (usually a log level) with ANSI color markers before to set the color and after to
/// reset the color.
///
/// WithFgColor instances can be created and displayed without any allocation.
// this is necessary in order to avoid using colored::ColorString, which has a Display
// implementation involving many allocations, and would involve two more string allocations
// even to create it.
pub struct WithFgColor<T>
where
T: fmt::Display,
{
text: T,
color: Color,
}
impl<T> fmt::Display for WithFgColor<T>
where
T: fmt::Display,
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "\x1B[{}m{}\x1B[0m", self.color.to_fg_str(), self.text)
}
}
/// Configuration specifying colors a log level can be colored as.
///
/// Example usage setting custom 'info' and 'debug' colors:
///
/// ```
/// use fern::colors::{Color, ColoredLogLevelConfig};
///
/// let colors = ColoredLogLevelConfig::new()
/// .info(Color::Green)
/// .debug(Color::Magenta);
///
/// fern::Dispatch::new()
/// .format(move |out, message, record| {
/// out.finish(format_args!(
/// "[{}] {}",
/// colors.color(record.level()),
/// message
/// ))
/// })
/// .chain(std::io::stdout())
/// # /*
/// .apply()?;
/// # */
/// # .into_log();
/// ```
#[derive(Copy, Clone)]
#[must_use = "builder methods take config by value and thus must be reassigned to variable"]
pub struct ColoredLogLevelConfig {
/// The color to color logs with the [`Error`] level.
///
/// [`Error`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Error
pub error: Color,
/// The color to color logs with the [`Warn`] level.
///
/// [`Warn`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Warn
pub warn: Color,
/// The color to color logs with the [`Info`] level.
///
/// [`Info`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Info
pub info: Color,
/// The color to color logs with the [`Debug`] level.
///
/// [`Debug`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Debug
pub debug: Color,
/// The color to color logs with the [`Trace`] level.
///
/// [`Trace`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Trace
pub trace: Color,
}
impl ColoredLogLevelConfig {
/// Creates a new ColoredLogLevelConfig with the default colors.
///
/// This matches the behavior of [`ColoredLogLevelConfig::default`].
///
/// [`ColoredLogLevelConfig::default`]: #method.default
#[inline]
pub fn new() -> Self {
Self::default()
}
/// Overrides the [`Error`] level color with the given color.
///
/// The default color is [`Color::Red`].
///
/// [`Error`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Error
/// [`Color::Red`]: https://docs.rs/colored/1/colored/enum.Color.html#variant.Red
pub fn error(mut self, error: Color) -> Self {
self.error = error;
self
}
/// Overrides the [`Warn`] level color with the given color.
///
/// The default color is [`Color::Yellow`].
///
/// [`Warn`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Warn
/// [`Color::Yellow`]: https://docs.rs/colored/1/colored/enum.Color.html#variant.Yellow
pub fn warn(mut self, warn: Color) -> Self {
self.warn = warn;
self
}
/// Overrides the [`Info`] level color with the given color.
///
/// The default color is [`Color::White`].
///
/// [`Info`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Info
/// [`Color::White`]: https://docs.rs/colored/1/colored/enum.Color.html#variant.White
pub fn info(mut self, info: Color) -> Self {
self.info = info;
self
}
/// Overrides the [`Debug`] level color with the given color.
///
/// The default color is [`Color::White`].
///
/// [`Debug`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Debug
/// [`Color::White`]: https://docs.rs/colored/1/colored/enum.Color.html#variant.White
pub fn debug(mut self, debug: Color) -> Self {
self.debug = debug;
self
}
/// Overrides the [`Trace`] level color with the given color.
///
/// The default color is [`Color::White`].
///
/// [`Trace`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Trace
/// [`Color::White`]: https://docs.rs/colored/1/colored/enum.Color.html#variant.White
pub fn trace(mut self, trace: Color) -> Self {
self.trace = trace;
self
}
/// Retrieves the default configuration. This has:
///
/// - [`Error`] as [`Color::Red`]
/// - [`Warn`] as [`Color::Yellow`]
/// - [`Info`] as [`Color::White`]
/// - [`Debug`] as [`Color::White`]
/// - [`Trace`] as [`Color::White`]
///
/// [`Error`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Error
/// [`Warn`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Warn
/// [`Info`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Info
/// [`Debug`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Debug
/// [`Trace`]: https://docs.rs/log/0.3/log/enum.LogLevel.html#variant.Trace
/// [`Color::White`]: https://docs.rs/colored/1/colored/enum.Color.html#variant.White
/// [`Color::Yellow`]: https://docs.rs/colored/1/colored/enum.Color.html#variant.Yellow
/// [`Color::Red`]: https://docs.rs/colored/1/colored/enum.Color.html#variant.Red
pub fn default() -> Self {
ColoredLogLevelConfig {
error: Color::Red,
warn: Color::Yellow,
debug: Color::White,
info: Color::White,
trace: Color::White,
}
}
/// Colors the given log level with the color in this configuration corresponding to it's
/// level.
///
/// The structure returned is opaque, but will print the LogLevel surrounded by ANSI color
/// codes when displayed. This will work correctly for UNIX terminals, but due to a lack
/// of support from the [`colored`] crate, this will not function in Windows.
///
/// [`colored`]: https://github.com/mackwic/colored
pub fn color(&self, level: LogLevel) -> WithFgColor<LogLevel> {
level.colored(self.get_color(&level))
}
/// Retrieves the color that a log level should be colored as.
pub fn get_color(&self, level: &LogLevel) -> Color {
match *level {
LogLevel::Error => self.error,
LogLevel::Warn => self.warn,
LogLevel::Info => self.info,
LogLevel::Debug => self.debug,
LogLevel::Trace => self.trace,
}
}
}
impl ColoredLogLevel for LogLevel {
fn colored(&self, color: Color) -> WithFgColor<LogLevel> {
WithFgColor {
text: *self,
color: color,
}
}
}
#[cfg(test)]
mod test {
use super::WithFgColor;
use colored::Colorize;
use colored::Color::*;
#[test]
fn fg_color_matches_colored_behavior() {
for &color in &[
Black,
Red,
Green,
Yellow,
Blue,
Magenta,
Cyan,
White,
BrightBlack,
BrightRed,
BrightGreen,
BrightYellow,
BrightBlue,
BrightMagenta,
BrightCyan,
BrightWhite,
] {
assert_eq!(
format!("{}", "test".color(color)),
format!(
"{}",
WithFgColor {
text: "test",
color: color,
}
)
);
}
}
}