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//! Minimal stderr logging utilities.
use std::{
cell::RefCell,
io::{self, Write},
};
/// Logging verbosity level.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum Verbosity {
/// Suppress warnings and informational messages.
Quiet,
/// Emit warnings but suppress informational messages.
Normal,
/// Emit warnings and informational messages.
Verbose,
}
/// Lightweight logger used by renderers and generators.
#[derive(Debug)]
pub struct Logger<W: Write> {
verbosity: Verbosity,
writer: RefCell<W>,
}
impl Logger<io::Stderr> {
/// Creates a logger with the given verbosity.
pub fn new(verbosity: Verbosity) -> Self {
Self {
verbosity,
writer: RefCell::new(io::stderr()),
}
}
}
impl<W: Write> Logger<W> {
pub fn with_writer(verbosity: Verbosity, writer: W) -> Self {
Self {
verbosity,
writer: RefCell::new(writer),
}
}
/// Emits a warning unless verbosity is [`Verbosity::Quiet`].
pub fn warn(&self, message: impl AsRef<str>) {
if self.verbosity != Verbosity::Quiet {
let _ = writeln!(self.writer.borrow_mut(), "Warning: {}", message.as_ref());
}
}
/// Emits an informational message only when verbosity is [`Verbosity::Verbose`].
pub fn info(&self, message: impl AsRef<str>) {
if self.verbosity == Verbosity::Verbose {
let _ = writeln!(self.writer.borrow_mut(), "Info: {}", message.as_ref());
}
}
}
#[cfg(test)]
mod tests {
use std::io::{self, Write};
use super::{Logger, Verbosity};
fn logged_output(logger: &Logger<Vec<u8>>) -> String {
String::from_utf8(logger.writer.borrow().clone()).unwrap()
}
#[test]
fn quiet_suppresses_warnings() {
let logger = Logger::with_writer(Verbosity::Quiet, Vec::new());
logger.warn("skipped file");
assert_eq!(logged_output(&logger), "");
}
#[test]
fn quiet_suppresses_info_messages() {
let logger = Logger::with_writer(Verbosity::Quiet, Vec::new());
logger.info("rendering file");
assert_eq!(logged_output(&logger), "");
}
#[test]
fn normal_writes_warnings() {
let logger = Logger::with_writer(Verbosity::Normal, Vec::new());
logger.warn("skipped file");
assert_eq!(logged_output(&logger), "Warning: skipped file\n");
}
#[test]
fn normal_suppresses_info_messages() {
let logger = Logger::with_writer(Verbosity::Normal, Vec::new());
logger.info("rendering file");
assert_eq!(logged_output(&logger), "");
}
#[test]
fn verbose_writes_warnings() {
let logger = Logger::with_writer(Verbosity::Verbose, Vec::new());
logger.warn("skipped file");
assert_eq!(logged_output(&logger), "Warning: skipped file\n");
}
#[test]
fn verbose_writes_info_messages() {
let logger = Logger::with_writer(Verbosity::Verbose, Vec::new());
logger.info("rendering file");
assert_eq!(logged_output(&logger), "Info: rendering file\n");
}
#[test]
fn verbose_preserves_log_order() {
let logger = Logger::with_writer(Verbosity::Verbose, Vec::new());
logger.info("rendering a.rs");
logger.warn("skipping duplicate file: a.rs");
logger.info("rendering b.rs");
assert_eq!(
logged_output(&logger),
"Info: rendering a.rs\n\
Warning: skipping duplicate file: a.rs\n\
Info: rendering b.rs\n"
);
}
struct FailingWriter;
impl Write for FailingWriter {
fn write(&mut self, _buf: &[u8]) -> io::Result<usize> {
Err(io::Error::other("intentional write failure"))
}
fn flush(&mut self) -> io::Result<()> {
Ok(())
}
}
#[test]
fn logging_ignores_writer_errors() {
let logger = Logger::with_writer(Verbosity::Verbose, FailingWriter);
logger.warn("this should not panic");
logger.info("this should not panic");
}
}
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