fix(core): purge JS event listeners when source webview is destroyed (fix #15583)

.changes/fix-js-listeners-leak-on-webview-close.md

@@ -0,0 +1,5 @@
+---
+'tauri': 'patch:bug'
+---
+
+Remove a webview's JS event listeners from the backend `Listeners` map when that webview is destroyed. Previously the entries keyed by the source webview label lingered after the webview was dropped, so they could never be delivered and leaked until the app exited — forcing apps to manually `unlisten()` before closing a window.

crates/tauri/src/event/listener.rs

@@ -251,6 +251,20 @@ impl Listeners {
     }
   }
 
+  /// Removes all JS event listeners registered from the given webview.
+  ///
+  /// Called when a webview is destroyed: its JavaScript runtime no longer
+  /// exists, so the listeners keyed by its label can never be delivered and
+  /// would otherwise leak in the map until the app exits.
+  pub(crate) fn remove_webview_js_listeners(&self, webview_label: &str) {
+    self
+      .inner
+      .js_event_listeners
+      .lock()
+      .unwrap()
+      .remove(webview_label);
+  }
+
   pub(crate) fn has_js_listener<F: Fn(&EventTarget) -> bool>(
     &self,
     event: crate::EventName<&str>,
@@ -398,4 +412,26 @@ mod test {
       .emit(EmitArgs::new(event.as_str_event(), &()).unwrap())
       .unwrap();
   }
+
+  #[test]
+  fn js_listeners_removed_on_webview_close() {
+    let listeners = Listeners::default();
+    let event = crate::EventName::new("some-event".to_owned()).unwrap();
+    let webview_label = "main";
+
+    let id = listeners.next_event_id();
+    listeners.listen_js(
+      event.as_str_event(),
+      webview_label,
+      EventTarget::Webview {
+        label: webview_label.to_owned(),
+      },
+      id,
+    );
+    assert!(listeners.has_js_listener(event.as_str_event(), |_| true));
+
+    // dropping the source webview must drop its JS listeners.
+    listeners.remove_webview_js_listeners(webview_label);
+    assert!(!listeners.has_js_listener(event.as_str_event(), |_| true));
+  }
 }

crates/tauri/src/manager/mod.rs

@@ -655,13 +655,17 @@ impl<R: Runtime> AppManager<R> {
     if let Some(window) = window {
       for webview in window.webviews() {
         self.webview.webviews_lock().remove(webview.label());
+        self
+          .listeners()
+          .remove_webview_js_listeners(webview.label());
       }
     }
   }
 
   #[cfg(desktop)]
   pub(crate) fn on_webview_close(&self, label: &str) {
     self.webview.webviews_lock().remove(label);
+    self.listeners().remove_webview_js_listeners(label);
   }
 
   pub fn windows(&self) -> HashMap<String, Window<R>> {