tor-config: Use a polling watcher on non-windows platforms that don't…

… have inotify.

On windows and platforms that support inotify (i.e. linux and android),
we continue using the recommended watcher. On platforms that use kqueue,
we switch to a polling watcher to work around a [notify bug] that
manifests when using a non-recursive watcher to watch a directory.

This commit is best reviewed with `git diff --ignore-all-space`.

Closes #1644

[notify bug]: notify-rs/notify#644

crates/tor-config/Cargo.toml

@@ -32,6 +32,7 @@ __is_experimental = []
 
 [dependencies]
 amplify = { version = "4", default-features = false, features = ["derive"] }
+cfg-if = "1.0.0"
 derive-deftly = "0.14"
 derive_builder = { version = "0.11.2", package = "derive_builder_fork_arti" }
 directories = { version = "5", optional = true }

crates/tor-config/src/file_watcher.rs

@@ -23,8 +23,15 @@ use futures::{SinkExt as _, Stream, StreamExt as _};
 /// `Result` whose `Err` is [`FileWatcherBuildError`].
 pub type Result<T> = std::result::Result<T, FileWatcherBuildError>;
 
-/// The concrete type of the underlying watcher.
-type NotifyWatcher = notify::RecommendedWatcher;
+cfg_if::cfg_if! {
+    if #[cfg(any(target_os = "linux", target_os = "android", target_os = "windows"))] {
+        /// The concrete type of the underlying watcher.
+        type NotifyWatcher = notify::RecommendedWatcher;
+    } else {
+        /// The concrete type of the underlying watcher.
+        type NotifyWatcher = notify::PollWatcher;
+    }
+}
 
 /// A wrapper around a `notify::Watcher` to watch a set of parent
 /// directories in order to learn about changes in some specific files that they