BUG: fixes get_instance_attributes for Flight objects containing a Rocket object without rail buttons (#786)

* DOC: fixed a typo in funcify_method() description

* TST: created test for get_instante_attributes() with flight without rail buttons

* BUG: fixed __calculate_rail_button_forces() by assigning a Function(0) to null_force instead of an empty array

* DEV: updates CHANGELOG

Author: leogrosa

CHANGELOG.md

@@ -44,8 +44,10 @@ Attention: The newest changes should be on top -->
 
 - BUG: do not allow drawing rockets with no aerodynamic surface [#774](https://github.com/RocketPy-Team/RocketPy/pull/774)
 - BUG: update flight simulation logic to include burn start time [#778](https://github.com/RocketPy-Team/RocketPy/pull/778)
+- BUG: fixes get_instance_attributes for Flight objects containing a Rocket object without rail buttons [#786](https://github.com/RocketPy-Team/RocketPy/pull/786)
 - BUG: fixed AGL altitude print for parachutes with lag [#788](https://github.com/RocketPy-Team/RocketPy/pull/788)
 
+
 ## [v1.8.0] - 2025-01-20
 
 To install this version, run `pip install rocketpy==1.8.0`

rocketpy/mathutils/function.py

@@ -3492,7 +3492,7 @@ def funcify_method(*args, **kwargs):  # pylint: disable=too-many-statements
     >>> example.f
     'Function from R1 to R1 : (x) → (f(x))'
 
-    In order to reset the cache, just delete de attribute from the instance:
+    In order to reset the cache, just delete the attribute from the instance:
 
     >>> del example.f
 

rocketpy/simulation/flight.py

@@ -2954,7 +2954,7 @@ def __calculate_rail_button_forces(self):  # TODO: complex method.
             Rail Button 2 force in the 2 direction
         """
         # First check for no rail phase or rail buttons
-        null_force = []
+        null_force = Function(0)
         if self.out_of_rail_time_index == 0:  # No rail phase, no rail button forces
             warnings.warn(
                 "Trying to calculate rail button forces without a rail phase defined."

tests/unit/test_utilities.py

@@ -165,7 +165,7 @@ def test_flutter_plots(mock_show, flight_calisto_custom_wind):  # pylint: disabl
     ), "An error occurred while running the utilities._flutter_plots function."
 
 
-def test_get_instance_attributes(flight_calisto_robust):
+def test_get_instance_attributes_with_robust_flight(flight_calisto_robust):
     """Tests if get_instance_attributes returns the expected results for a
     robust flight object."""
 
@@ -178,6 +178,19 @@ def test_get_instance_attributes(flight_calisto_robust):
             assert attr == value
 
 
+def test_get_instance_attributes_with_flight_without_rail_buttons(flight_calisto):
+    """Tests if get_instance_attributes returns the expected results for a
+    flight object that contains a rocket object without rail buttons."""
+
+    attributes = utilities.get_instance_attributes(flight_calisto)
+    for key, value in attributes.items():
+        attr = getattr(flight_calisto, key)
+        if isinstance(attr, np.ndarray):
+            assert np.allclose(attr, value)
+        else:
+            assert attr == value
+
+
 @pytest.mark.parametrize(
     "f, eps, expected",
     [