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file_watcher.rs
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file_watcher.rs
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// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
use crate::colors;
use crate::fs_util::canonicalize_path;
use deno_core::error::AnyError;
use deno_core::futures::stream::{Stream, StreamExt};
use deno_core::futures::Future;
use deno_core::parking_lot::Mutex;
use log::info;
use notify::event::Event as NotifyEvent;
use notify::event::EventKind;
use notify::Config;
use notify::Error as NotifyError;
use notify::RecommendedWatcher;
use notify::RecursiveMode;
use notify::Watcher;
use pin_project::pin_project;
use std::collections::HashSet;
use std::path::PathBuf;
use std::pin::Pin;
use std::sync::Arc;
use std::task::Context;
use std::task::Poll;
use std::time::Duration;
use tokio::pin;
use tokio::select;
use tokio::time::sleep;
use tokio::time::Instant;
use tokio::time::Sleep;
const DEBOUNCE_INTERVAL: Duration = Duration::from_millis(200);
#[pin_project(project = DebounceProjection)]
struct Debounce {
#[pin]
timer: Sleep,
changed_paths: Arc<Mutex<HashSet<PathBuf>>>,
}
impl Debounce {
fn new() -> Self {
Self {
timer: sleep(DEBOUNCE_INTERVAL),
changed_paths: Arc::new(Mutex::new(HashSet::new())),
}
}
}
impl Stream for Debounce {
type Item = Vec<PathBuf>;
/// Note that this never returns `Poll::Ready(None)`, which means that the
/// file watcher will be alive until the Deno process is terminated.
fn poll_next(
self: Pin<&mut Self>,
cx: &mut Context,
) -> Poll<Option<Self::Item>> {
let mut changed_paths = self.changed_paths.lock();
if changed_paths.len() > 0 {
Poll::Ready(Some(changed_paths.drain().collect()))
} else {
drop(changed_paths);
let mut timer = self.project().timer;
if timer.as_mut().poll(cx).is_ready() {
timer.reset(Instant::now() + DEBOUNCE_INTERVAL);
}
Poll::Pending
}
}
}
async fn error_handler<F>(watch_future: F)
where
F: Future<Output = Result<(), AnyError>>,
{
let result = watch_future.await;
if let Err(err) = result {
let msg = format!("{}: {}", colors::red_bold("error"), err.to_string(),);
eprintln!("{}", msg);
}
}
pub enum ResolutionResult<T> {
Restart {
paths_to_watch: Vec<PathBuf>,
result: Result<T, AnyError>,
},
Ignore,
}
async fn next_restart<R, T, F>(
resolver: &mut R,
debounce: &mut Pin<&mut Debounce>,
) -> (Vec<PathBuf>, Result<T, AnyError>)
where
R: FnMut(Option<Vec<PathBuf>>) -> F,
F: Future<Output = ResolutionResult<T>>,
{
loop {
let changed = debounce.next().await;
match resolver(changed).await {
ResolutionResult::Ignore => {
log::debug!("File change ignored")
}
ResolutionResult::Restart {
paths_to_watch,
result,
} => {
info!(
"{} File change detected! Restarting!",
colors::intense_blue("Watcher"),
);
return (paths_to_watch, result);
}
}
}
}
/// Creates a file watcher, which will call `resolver` with every file change.
///
/// - `resolver` is used for resolving file paths to be watched at every restarting
/// of the watcher, and can also return a value to be passed to `operation`.
/// It returns a [`ResolutionResult`], which can either instruct the watcher to restart or ignore the change.
/// This always contains paths to watch;
///
/// - `operation` is the actual operation we want to run every time the watcher detects file
/// changes. For example, in the case where we would like to bundle, then `operation` would
/// have the logic for it like bundling the code.
///
/// - `job_name` is just used for printing watcher status to terminal.
pub async fn watch_func<R, O, T, F1, F2>(
mut resolver: R,
mut operation: O,
job_name: &str,
) -> Result<(), AnyError>
where
R: FnMut(Option<Vec<PathBuf>>) -> F1,
O: FnMut(T) -> F2,
F1: Future<Output = ResolutionResult<T>>,
F2: Future<Output = Result<(), AnyError>>,
{
let debounce = Debounce::new();
pin!(debounce);
// Store previous data. If module resolution fails at some point, the watcher will try to
// continue watching files using these data.
let mut paths_to_watch;
let mut resolution_result;
match resolver(None).await {
ResolutionResult::Ignore => {
// The only situation where it makes sense to ignore the initial 'change'
// is if the command isn't supposed to do anything until something changes,
// e.g. a variant of `deno test` which doesn't run the entire test suite to start with,
// but instead does nothing until you make a change.
//
// In that case, this is probably the correct output.
info!(
"{} Waiting for file changes...",
colors::intense_blue("Watcher"),
);
let (paths, result) = next_restart(&mut resolver, &mut debounce).await;
paths_to_watch = paths;
resolution_result = result;
}
ResolutionResult::Restart {
paths_to_watch: paths,
result,
} => {
paths_to_watch = paths;
resolution_result = result;
}
};
loop {
let watcher = new_watcher(&paths_to_watch, &debounce)?;
match resolution_result {
Ok(operation_arg) => {
let fut = error_handler(operation(operation_arg));
select! {
(paths, result) = next_restart(&mut resolver, &mut debounce) => {
if result.is_ok() {
paths_to_watch = paths;
}
resolution_result = result;
continue;
},
_ = fut => {},
};
info!(
"{} {} finished. Restarting on file change...",
colors::intense_blue("Watcher"),
job_name,
);
}
Err(error) => {
eprintln!("{}: {}", colors::red_bold("error"), error);
info!(
"{} {} failed. Restarting on file change...",
colors::intense_blue("Watcher"),
job_name,
);
}
}
let (paths, result) = next_restart(&mut resolver, &mut debounce).await;
if result.is_ok() {
paths_to_watch = paths;
}
resolution_result = result;
drop(watcher);
}
}
fn new_watcher(
paths: &[PathBuf],
debounce: &Debounce,
) -> Result<RecommendedWatcher, AnyError> {
let changed_paths = Arc::clone(&debounce.changed_paths);
let mut watcher: RecommendedWatcher =
Watcher::new(move |res: Result<NotifyEvent, NotifyError>| {
if let Ok(event) = res {
if matches!(
event.kind,
EventKind::Create(_) | EventKind::Modify(_) | EventKind::Remove(_)
) {
let paths = event
.paths
.iter()
.filter_map(|path| canonicalize_path(path).ok());
let mut changed_paths = changed_paths.lock();
changed_paths.extend(paths);
}
}
})?;
watcher.configure(Config::PreciseEvents(true)).unwrap();
log::debug!("Watching paths: {:?}", paths);
for path in paths {
// Ignore any error e.g. `PathNotFound`
let _ = watcher.watch(path, RecursiveMode::Recursive);
}
Ok(watcher)
}