Add Watcher::kind()

Cargo.toml

@@ -63,5 +63,6 @@ notify = { path = "." }
 [workspace]
 members = [
   ".",
-  "examples/hot_reload_tide"
+  "examples/hot_reload_tide",
+  "examples/watcher_kind"
 ]

examples/watcher_kind/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "watcher_kind"
+version = "0.1.0"
+authors = ["Aron Heinecke <aron.heinecke@t-online.de>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+notify = { version = "5.0.0-pre.13", path = "../../" }

examples/watcher_kind/src/main.rs

@@ -0,0 +1,11 @@
+use std::time::Duration;
+
+use notify::*;
+fn main() {
+    let (tx, rx) = std::sync::mpsc::channel();
+    let watcher: Box<dyn Watcher> = if RecommendedWatcher::kind() == WatcherKind::PollWatcher {
+        Box::new(PollWatcher::with_delay(tx,Duration::from_secs(1)).unwrap())
+    } else {
+        Box::new(RecommendedWatcher::new(tx).unwrap())
+    };
+}

src/fsevent.rs

@@ -542,6 +542,10 @@ impl Watcher for FsEventWatcher {
         self.configure_raw_mode(config, tx);
         rx.recv()?
     }
+
+    fn kind() -> crate::WatcherKind {
+        crate::WatcherKind::Fsevent
+    }
 }
 
 impl Drop for FsEventWatcher {

src/inotify.rs

@@ -619,6 +619,10 @@ impl Watcher for INotifyWatcher {
         self.waker.wake()?;
         rx.recv()?
     }
+
+    fn kind() -> crate::WatcherKind {
+        crate::WatcherKind::Inotify
+    }
 }
 
 impl Drop for INotifyWatcher {

src/kqueue.rs

@@ -386,6 +386,10 @@ impl Watcher for KqueueWatcher {
     fn unwatch(&mut self, path: &Path) -> Result<()> {
         self.unwatch_inner(path)
     }
+
+    fn kind() -> crate::WatcherKind {
+        crate::WatcherKind::Kqueue
+    }
 }
 
 impl Drop for KqueueWatcher {

src/lib.rs

@@ -185,6 +185,24 @@ impl EventHandler for std::sync::mpsc::Sender<Result<Event>> {
     }
 }
 
+/// Watcher kind enumeration
+#[derive(Debug,PartialEq,Eq)]
+#[non_exhaustive]
+pub enum WatcherKind {
+    /// inotify backend (linux)
+    Inotify,
+    /// FS-Event backend (mac)
+    Fsevent,
+    /// KQueue backend (bsd,mac)
+    Kqueue,
+    /// Polling based backend (fallback)
+    PollWatcher,
+    /// Windows backend
+    ReadDirectoryChangesWatcher,
+    /// Fake watcher for testing
+    NullWatcher,
+}
+
 /// Type that can deliver file activity notifications
 ///
 /// Watcher is implemented per platform using the best implementation available on that platform.
@@ -232,6 +250,9 @@ pub trait Watcher {
     fn configure(&mut self, _option: Config) -> Result<bool> {
         Ok(false)
     }
+
+    /// Returns the watcher kind, allowing to perform backend-specific tasks
+    fn kind() -> WatcherKind where Self: Sized;
 }
 
 /// The recommended `Watcher` implementation for the current platform

src/null.rs

@@ -22,4 +22,8 @@ impl Watcher for NullWatcher {
     fn new<F: crate::EventHandler>(event_handler: F) -> Result<Self> where Self: Sized {
         Ok(NullWatcher)
     }
+
+    fn kind() -> crate::WatcherKind {
+        crate::WatcherKind::NullWatcher
+    }
 }

src/poll.rs

@@ -288,6 +288,10 @@ impl Watcher for PollWatcher {
     fn unwatch(&mut self, path: &Path) -> Result<()> {
         self.unwatch_inner(path)
     }
+
+    fn kind() -> crate::WatcherKind {
+        crate::WatcherKind::PollWatcher
+    }
 }
 
 impl Drop for PollWatcher {

src/windows.rs

@@ -15,7 +15,7 @@ use winapi::um::synchapi;
 use winapi::um::winbase::{self, INFINITE, WAIT_OBJECT_0};
 use winapi::um::winnt::{self, FILE_NOTIFY_INFORMATION, HANDLE};
 
-use crate::event::*;
+use crate::{WatcherKind, event::*};
 use crate::{Config, Error, EventHandler, RecursiveMode, Result, Watcher};
 use crossbeam_channel::{bounded, unbounded, Receiver, Sender};
 use std::collections::HashMap;
@@ -512,6 +512,10 @@ impl Watcher for ReadDirectoryChangesWatcher {
         self.tx.send(Action::Configure(config, tx))?;
         rx.recv()?
     }
+
+    fn kind() -> crate::WatcherKind {
+        WatcherKind::ReadDirectoryChangesWatcher
+    }
 }
 
 impl Drop for ReadDirectoryChangesWatcher {