feat: unwatch return boolean

src/database.rs

@@ -79,12 +79,12 @@ impl Database<'_> {
 
     /// Unwatch the given `id`.
     /// You can get the `id` from the return value of [`watch`](Self::watch).
-    /// If the `id` is not valid anymore, this function will do nothing.
-    /// If the `id` is valid, the corresponding watcher will be removed.
-    pub fn unwatch(&self, id: u64) -> Result<()> {
+    /// If the `id` is not valid anymore, this function will do nothing and return `false`.
+    /// If the `id` is valid, the corresponding watcher will be removed and return `true`.
+    /// If the `id` is valid but the watcher is already removed, this function will return `false`.
+    pub fn unwatch(&self, id: u64) -> Result<bool> {
         let mut watchers = self.watchers.write().unwrap();
-        watchers.remove_sender(id);
-        Ok(())
+        Ok(watchers.remove_sender(id))
     }
 }
 

src/watch/sender.rs

@@ -21,8 +21,8 @@ impl Watchers {
         self.0.insert(id, (table_filter.clone(), event_sender));
     }
 
-    pub(crate) fn remove_sender(&mut self, id: u64) {
-        self.0.remove(&id);
+    pub(crate) fn remove_sender(&mut self, id: u64) -> bool {
+        self.0.remove(&id).is_some()
     }
 
     pub(crate) fn find_senders(

tests/watch/mod.rs

@@ -284,7 +284,7 @@ fn unwatch() {
         assert_eq!(inner_event, item_a);
     }
 
-    db.unwatch(recv_id).unwrap();
+    assert!(db.unwatch(recv_id).unwrap());
 
     let rw = db.rw_transaction().unwrap();
     rw.insert(item_a.clone()).unwrap();