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//! Control `log` level with a `--verbose` flag for your CLI
//!
//! # Examples
//!
//! To get `--quiet` and `--verbose` flags through your entire program, just `flatten`
//! [`Verbosity`]:
//! ```rust,no_run
//! # use clap::Parser;
//! # use clap_verbosity_flag::Verbosity;
//! #
//! # /// Le CLI
//! # #[derive(Debug, Parser)]
//! # struct Cli {
//! #[command(flatten)]
//! verbose: Verbosity,
//! # }
//! ```
//!
//! You can then use this to configure your logger:
//! ```rust,no_run
//! # use clap::Parser;
//! # use clap_verbosity_flag::Verbosity;
//! #
//! # /// Le CLI
//! # #[derive(Debug, Parser)]
//! # struct Cli {
//! # #[command(flatten)]
//! # verbose: Verbosity,
//! # }
//! let cli = Cli::parse();
//! env_logger::Builder::new()
//! .filter_level(cli.verbose.log_level_filter())
//! .init();
//! ```
//!
//! By default, this will only report errors.
//! - `-q` silences output
//! - `-v` show warnings
//! - `-vv` show info
//! - `-vvv` show debug
//! - `-vvvv` show trace
//!
//! You can also customize the default logging level:
//! ```rust,no_run
//! # use clap::Parser;
//! use clap_verbosity_flag::{Verbosity, InfoLevel};
//!
//! /// Le CLI
//! #[derive(Debug, Parser)]
//! struct Cli {
//! #[command(flatten)]
//! verbose: Verbosity<InfoLevel>,
//! }
//! ```
//!
//! Or implement our [`LogLevel`] trait to customize the default log level and help output.
#![cfg_attr(docsrs, feature(doc_auto_cfg))]
pub use log::Level;
pub use log::LevelFilter;
/// Logging flags to `#[command(flatten)]` into your CLI
#[derive(clap::Args, Debug, Clone, Default)]
#[command(about = None, long_about = None)]
pub struct Verbosity<L: LogLevel = ErrorLevel> {
#[arg(
long,
short = 'v',
action = clap::ArgAction::Count,
global = true,
help = L::verbose_help(),
long_help = L::verbose_long_help(),
)]
verbose: u8,
#[arg(
long,
short = 'q',
action = clap::ArgAction::Count,
global = true,
help = L::quiet_help(),
long_help = L::quiet_long_help(),
conflicts_with = "verbose",
)]
quiet: u8,
#[arg(skip)]
phantom: std::marker::PhantomData<L>,
}
impl<L: LogLevel> Verbosity<L> {
/// Create a new verbosity instance by explicitly setting the values
pub fn new(verbose: u8, quiet: u8) -> Self {
Verbosity {
verbose,
quiet,
phantom: std::marker::PhantomData,
}
}
/// Whether any verbosity flags (either `--verbose` or `--quiet`)
/// are present on the command line.
pub fn is_present(&self) -> bool {
self.verbose != 0 || self.quiet != 0
}
/// Get the log level.
///
/// `None` means all output is disabled.
pub fn log_level(&self) -> Option<log::Level> {
level_enum(self.verbosity())
}
/// Get the log level filter.
pub fn log_level_filter(&self) -> log::LevelFilter {
level_enum(self.verbosity())
.map(|l| l.to_level_filter())
.unwrap_or(log::LevelFilter::Off)
}
/// If the user requested complete silence (i.e. not just no-logging).
pub fn is_silent(&self) -> bool {
self.log_level().is_none()
}
fn verbosity(&self) -> i8 {
level_value(L::default()) - (self.quiet as i8) + (self.verbose as i8)
}
}
fn level_value(level: Option<log::Level>) -> i8 {
match level {
None => -1,
Some(log::Level::Error) => 0,
Some(log::Level::Warn) => 1,
Some(log::Level::Info) => 2,
Some(log::Level::Debug) => 3,
Some(log::Level::Trace) => 4,
}
}
fn level_enum(verbosity: i8) -> Option<log::Level> {
match verbosity {
std::i8::MIN..=-1 => None,
0 => Some(log::Level::Error),
1 => Some(log::Level::Warn),
2 => Some(log::Level::Info),
3 => Some(log::Level::Debug),
4..=std::i8::MAX => Some(log::Level::Trace),
}
}
use std::fmt;
impl<L: LogLevel> fmt::Display for Verbosity<L> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "{}", self.verbosity())
}
}
/// Customize the default log-level and associated help
pub trait LogLevel {
fn default() -> Option<log::Level>;
fn verbose_help() -> Option<&'static str> {
Some("Increase logging verbosity")
}
fn verbose_long_help() -> Option<&'static str> {
None
}
fn quiet_help() -> Option<&'static str> {
Some("Decrease logging verbosity")
}
fn quiet_long_help() -> Option<&'static str> {
None
}
}
/// Default to [`log::Level::Error`]
#[derive(Copy, Clone, Debug, Default)]
pub struct ErrorLevel;
impl LogLevel for ErrorLevel {
fn default() -> Option<log::Level> {
Some(log::Level::Error)
}
}
/// Default to [`log::Level::Warn`]
#[derive(Copy, Clone, Debug, Default)]
pub struct WarnLevel;
impl LogLevel for WarnLevel {
fn default() -> Option<log::Level> {
Some(log::Level::Warn)
}
}
/// Default to [`log::Level::Info`]
#[derive(Copy, Clone, Debug, Default)]
pub struct InfoLevel;
impl LogLevel for InfoLevel {
fn default() -> Option<log::Level> {
Some(log::Level::Info)
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn verify_app() {
#[derive(Debug, clap::Parser)]
struct Cli {
#[command(flatten)]
verbose: Verbosity,
}
use clap::CommandFactory;
Cli::command().debug_assert()
}
}