1 files changed, 92 insertions, 0 deletions
diff --git a/cli/file_watcher.rs b/cli/file_watcher.rs
new file mode 100644
index 000000000..892d0d4a1
--- /dev/null
+++ b/cli/file_watcher.rs
@@ -0,0 +1,92 @@
+use crate::colors;
+use deno_core::ErrBox;
+use futures::stream::StreamExt;
+use futures::Future;
+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 std::path::PathBuf;
+use std::pin::Pin;
+use tokio::select;
+use tokio::sync::mpsc;
+
+// TODO(bartlomieju): rename
+type WatchFuture =
+  Pin<Box<dyn Future<Output = std::result::Result<(), deno_core::ErrBox>>>>;
+
+async fn error_handler(watch_future: WatchFuture) {
+  let result = watch_future.await;
+  if let Err(err) = result {
+    let msg = format!("{}: {}", colors::red_bold("error"), err.to_string(),);
+    eprintln!("{}", msg);
+  }
+}
+
+pub async fn watch_func<F>(
+  watch_paths: &[PathBuf],
+  closure: F,
+) -> Result<(), ErrBox>
+where
+  F: Fn() -> WatchFuture,
+{
+  loop {
+    let func = error_handler(closure());
+    let mut is_file_changed = false;
+    select! {
+      _ = file_watcher(watch_paths) => {
+          is_file_changed = true;
+          info!(
+            "{} File change detected! Restarting!",
+            colors::intense_blue("Watcher")
+          );
+        },
+      _ = func => { },
+    };
+    if !is_file_changed {
+      info!(
+        "{} Process terminated! Restarting on file change...",
+        colors::intense_blue("Watcher")
+      );
+      file_watcher(watch_paths).await?;
+      info!(
+        "{} File change detected! Restarting!",
+        colors::intense_blue("Watcher")
+      );
+    }
+  }
+}
+
+pub async fn file_watcher(paths: &[PathBuf]) -> Result<(), deno_core::ErrBox> {
+  let (sender, mut receiver) = mpsc::channel::<Result<NotifyEvent, ErrBox>>(16);
+  let sender = std::sync::Mutex::new(sender);
+
+  let mut watcher: RecommendedWatcher =
+    Watcher::new_immediate(move |res: Result<NotifyEvent, NotifyError>| {
+      let res2 = res.map_err(ErrBox::from);
+      let mut sender = sender.lock().unwrap();
+      // Ignore result, if send failed it means that watcher was already closed,
+      // but not all messages have been flushed.
+      let _ = sender.try_send(res2);
+    })?;
+
+  watcher.configure(Config::PreciseEvents(true)).unwrap();
+
+  for path in paths {
+    watcher.watch(path, RecursiveMode::NonRecursive)?;
+  }
+
+  while let Some(result) = receiver.next().await {
+    let event = result?;
+    match event.kind {
+      EventKind::Create(_) => break,
+      EventKind::Modify(_) => break,
+      EventKind::Remove(_) => break,
+      _ => continue,
+    }
+  }
+  Ok(())
+}