Add test + doc for Signal/Callable::object_id() on dead objects

godot-core/src/builtin/callable.rs

@@ -205,8 +205,8 @@ impl Callable {
 
     /// Returns the object on which this callable is called.
     ///
-    /// Returns `None` when this callable doesn't have any target object to call a method on, regardless of
-    /// if the method exists for that target or not.
+    /// Returns `None` when this callable doesn't have any target object to call a method on (regardless of whether the method exists for that
+    /// target or not). Also returns `None` if the object is dead. You can differentiate these two cases using [`object_id()`][Self::object_id].
     ///
     /// _Godot equivalent: `get_object`_
     pub fn object(&self) -> Option<Gd<Object>> {
@@ -222,6 +222,8 @@ impl Callable {
     ///
     /// Returns `None` when this callable doesn't have any target to call a method on.
     ///
+    /// If the pointed-to object is dead, the ID will still be returned. Use [`object()`][Self::object] to check for liveness.
+    ///
     /// _Godot equivalent: `get_object_id`_
     pub fn object_id(&self) -> Option<InstanceId> {
         let id = self.as_inner().get_object_id();

godot-core/src/builtin/signal.rs

@@ -121,7 +121,8 @@ impl Signal {
 
     /// Returns the object to which this signal belongs.
     ///
-    /// Returns [`None`] when this signal doesn't have any object.
+    /// Returns [`None`] when this signal doesn't have any object, or the object is dead. You can differentiate these two situations using
+    /// [`object_id()`][Self::object_id].
     ///
     /// _Godot equivalent: `get_object`_
     pub fn object(&self) -> Option<Gd<Object>> {
@@ -135,6 +136,8 @@ impl Signal {
     ///
     /// Returns [`None`] when this signal doesn't have any object.
     ///
+    /// If the pointed-to object is dead, the ID will still be returned. Use [`object()`][Self::object] to check for liveness.
+    ///
     /// _Godot equivalent: `get_object_id`_
     pub fn object_id(&self) -> Option<InstanceId> {
         let id = self.as_inner().get_object_id();

itest/rust/src/builtin_tests/containers/callable_test.rs

@@ -67,13 +67,19 @@ fn callable_hash() {
 
 #[itest]
 fn callable_object_method() {
-    let obj = CallableTestObj::new_gd();
-    let callable = obj.callable("foo");
+    let object = CallableTestObj::new_gd();
+    let object_id = object.instance_id();
+    let callable = object.callable("foo");
 
-    assert_eq!(callable.object(), Some(obj.clone().upcast::<Object>()));
-    assert_eq!(callable.object_id(), Some(obj.instance_id()));
+    assert_eq!(callable.object(), Some(object.clone().upcast::<Object>()));
+    assert_eq!(callable.object_id(), Some(object_id));
     assert_eq!(callable.method_name(), Some("foo".into()));
 
+    // Invalidating the object still returns the old ID, however not the object.
+    drop(object);
+    assert_eq!(callable.object_id(), Some(object_id));
+    assert_eq!(callable.object(), None);
+
     assert_eq!(Callable::invalid().object(), None);
     assert_eq!(Callable::invalid().object_id(), None);
     assert_eq!(Callable::invalid().method_name(), None);

itest/rust/src/builtin_tests/containers/signal_test.rs

@@ -95,15 +95,21 @@ fn signals() {
 #[itest]
 fn instantiate_signal() {
     let mut object = RefCounted::new_gd();
+    let object_id = object.instance_id();
 
     object.add_user_signal("test_signal".into());
 
     let signal = Signal::from_object_signal(&object, "test_signal");
 
     assert!(!signal.is_null());
     assert_eq!(signal.name(), StringName::from("test_signal"));
-    assert_eq!(signal.object().unwrap(), object.clone().upcast());
-    assert_eq!(signal.object_id().unwrap(), object.instance_id());
+    assert_eq!(signal.object(), Some(object.clone().upcast()));
+    assert_eq!(signal.object_id(), Some(object_id));
+
+    // Invalidating the object still returns the old ID, however not the object.
+    drop(object);
+    assert_eq!(signal.object_id(), Some(object_id));
+    assert_eq!(signal.object(), None);
 }
 
 #[itest]