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// This module defines a super simple logger that works with the `log` crate.
// We don't need anything fancy; just basic log levels and the ability to
// print to stderr. We therefore avoid bringing in extra dependencies just
// for this functionality.
use log::{self, Log};
/// The simplest possible logger that logs to stderr.
///
/// This logger does no filtering. Instead, it relies on the `log` crates
/// filtering via its global max_level setting.
#[derive(Debug)]
pub struct Logger(());
const LOGGER: &'static Logger = &Logger(());
impl Logger {
/// Create a new logger that logs to stderr and initialize it as the
/// global logger. If there was a problem setting the logger, then an
/// error is returned.
pub fn init() -> Result<(), log::SetLoggerError> {
log::set_logger(LOGGER)
}
}
impl Log for Logger {
fn enabled(&self, _: &log::Metadata<'_>) -> bool {
// We set the log level via log::set_max_level, so we don't need to
// implement filtering here.
true
}
fn log(&self, record: &log::Record<'_>) {
match (record.file(), record.line()) {
(Some(file), Some(line)) => {
eprintln_locked!(
"{}|{}|{}:{}: {}",
record.level(),
record.target(),
file,
line,
record.args()
);
}
(Some(file), None) => {
eprintln_locked!(
"{}|{}|{}: {}",
record.level(),
record.target(),
file,
record.args()
);
}
_ => {
eprintln_locked!(
"{}|{}: {}",
record.level(),
record.target(),
record.args()
);
}
}
}
fn flush(&self) {
// We use eprintln_locked! which is flushed on every call.
}
}