Split known create errors to get proper help text

lib/src/error/specialised.rs

@@ -133,20 +133,38 @@ impl From<TaggedFiltererError> for RuntimeError {
 #[diagnostic(url(docsrs))]
 pub enum FsWatcherError {
 	/// Error received when creating a filesystem watcher fails.
+	///
+	/// Also see `TooManyWatches` and `TooManyHandles`.
 	#[error("failed to instantiate")]
 	#[diagnostic(
 		code(watchexec::fs_watcher::create),
 		help("perhaps retry with the poll watcher")
 	)]
-	Create {
+	Create(#[source] notify::Error),
-		/// The underlying error.
-		#[source]
-		err: notify::Error,
 
-		/// A hint to the user about resolving the error.
+	/// Error received when creating or updating a filesystem watcher fails because there are too many watches.
-		#[source_code]
+	///
-		help: String,
+	/// This is the OS error 28 on Linux.
-	},
+	#[error("failed to instantiate: too many watches")]
+	#[diagnostic(code(watchexec::fs_watcher::too_many_watches))]
+	#[cfg_attr(target_os = "linux", diagnostic(help("you will want to increase your inotify.max_user_watches, see inotify(7) and https://watchexec.github.io/docs/inotify-limits.html")))]
+	#[cfg_attr(
+		not(target_os = "linux"),
+		diagnostic(help("this should not happen on your platform"))
+	)]
+	TooManyWatches(#[source] notify::Error),
+
+	/// Error received when creating or updating a filesystem watcher fails because there are too many file handles open.
+	///
+	/// This is the OS error 24 on Linux. It may also occur when the limit for inotify instances is reached.
+	#[error("failed to instantiate: too many handles")]
+	#[diagnostic(code(watchexec::fs_watcher::too_many_handles))]
+	#[cfg_attr(target_os = "linux", diagnostic(help("you will want to increase your `nofile` limit, see pam_limits(8); or increase your inotify.max_user_instances, see inotify(7) and https://watchexec.github.io/docs/inotify-limits.html")))]
+	#[cfg_attr(
+		not(target_os = "linux"),
+		diagnostic(help("this should not happen on your platform"))
+	)]
+	TooManyHandles(#[source] notify::Error),
 
 	/// Error received when reading a filesystem event fails.
 	#[error("received an event that we could not read")]

lib/src/fs.rs

@@ -53,16 +53,19 @@ impl Watcher {
 		}
 		.map_err(|err| RuntimeError::FsWatcher {
 			kind: self,
-			err: FsWatcherError::Create {
+			err: if cfg!(target_os = "linux")
-			help: if cfg!(target_os = "linux") && (matches!(err.kind, notify::ErrorKind::MaxFilesWatch) || matches!(err.kind, notify::ErrorKind::Io(ref ioerr) if ioerr.raw_os_error() == Some(28))) {
+				&& (matches!(err.kind, notify::ErrorKind::MaxFilesWatch)
-				"you will want to increase your inotify.max_user_watches, see inotify(7) and https://watchexec.github.io/docs/inotify-limits.html"
+					|| matches!(err.kind, notify::ErrorKind::Io(ref ioerr) if ioerr.raw_os_error() == Some(28)))
-			} else if cfg!(target_os = "linux") && matches!(err.kind, notify::ErrorKind::Io(ref ioerr) if ioerr.raw_os_error() == Some(24)) {
+			{
-				"you will want to increase your `nofile` limit, see pam_limits(8)"
+				FsWatcherError::TooManyWatches(err)
+			} else if cfg!(target_os = "linux")
+				&& matches!(err.kind, notify::ErrorKind::Io(ref ioerr) if ioerr.raw_os_error() == Some(24))
+			{
+				FsWatcherError::TooManyHandles(err)
 			} else {
-				"you may want to try again with the polling watcher"
+				FsWatcherError::Create(err)
-			}.into(),
+			},
-			err,
+		})
-		}})
 	}
 }