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use std::io;
pub trait MakeWriter {
type Writer: io::Write;
fn make_writer(&self) -> Self::Writer;
}
impl<F, W> MakeWriter for F
where
F: Fn() -> W,
W: io::Write,
{
type Writer = W;
fn make_writer(&self) -> Self::Writer {
(self)()
}
}
#[cfg(test)]
mod test {
use super::MakeWriter;
use crate::fmt::Subscriber;
use lazy_static::lazy_static;
use std::io;
use std::sync::{Mutex, MutexGuard, TryLockError};
use tracing::error;
use tracing_core::dispatcher::{self, Dispatch};
fn test_writer<T>(make_writer: T, msg: &str, buf: &Mutex<Vec<u8>>)
where
T: MakeWriter + Send + Sync + 'static,
{
let subscriber = Subscriber::builder()
.with_writer(make_writer)
.without_time()
.with_ansi(false)
.finish();
let dispatch = Dispatch::from(subscriber);
dispatcher::with_default(&dispatch, || {
error!("{}", msg);
});
let expected = format!("ERROR {}: {}\n", module_path!(), msg);
let actual = String::from_utf8(buf.try_lock().unwrap().to_vec()).unwrap();
assert!(actual.contains(expected.as_str()));
}
struct MockWriter<'a> {
buf: &'a Mutex<Vec<u8>>,
}
impl<'a> MockWriter<'a> {
fn new(buf: &'a Mutex<Vec<u8>>) -> Self {
Self { buf }
}
fn map_error<Guard>(err: TryLockError<Guard>) -> io::Error {
match err {
TryLockError::WouldBlock => io::Error::from(io::ErrorKind::WouldBlock),
TryLockError::Poisoned(_) => io::Error::from(io::ErrorKind::Other),
}
}
fn buf(&self) -> io::Result<MutexGuard<'a, Vec<u8>>> {
self.buf.try_lock().map_err(Self::map_error)
}
}
impl<'a> io::Write for MockWriter<'a> {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
self.buf()?.write(buf)
}
fn flush(&mut self) -> io::Result<()> {
self.buf()?.flush()
}
}
struct MockMakeWriter<'a> {
buf: &'a Mutex<Vec<u8>>,
}
impl<'a> MockMakeWriter<'a> {
fn new(buf: &'a Mutex<Vec<u8>>) -> Self {
Self { buf }
}
}
impl<'a> MakeWriter for MockMakeWriter<'a> {
type Writer = MockWriter<'a>;
fn make_writer(&self) -> Self::Writer {
MockWriter::new(self.buf)
}
}
#[test]
fn custom_writer_closure() {
lazy_static! {
static ref BUF: Mutex<Vec<u8>> = Mutex::new(vec![]);
}
let make_writer = || MockWriter::new(&BUF);
let msg = "my custom writer closure error";
test_writer(make_writer, msg, &BUF);
}
#[test]
fn custom_writer_struct() {
lazy_static! {
static ref BUF: Mutex<Vec<u8>> = Mutex::new(vec![]);
}
let make_writer = MockMakeWriter::new(&BUF);
let msg = "my custom writer struct error";
test_writer(make_writer, msg, &BUF);
}
}