Enh/custom warning no motor parachute aerosurface

CHANGELOG.md

@@ -31,6 +31,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 Attention: The newest changes should be on top -->
 
 ### Added
+- ENH: Custom Exception errors and messages [#285](https://github.com/RocketPy-Team/RocketPy/issues/285)
 - ENH: Tank Fluids with Variable Density from Temperature and Pressure [#852](https://github.com/RocketPy-Team/RocketPy/pull/852)
 - ENH: Controller (AirBrakes) and Sensors Encoding [#849](https://github.com/RocketPy-Team/RocketPy/pull/849)
 - EHN: Addition of ensemble variable to ECMWF dictionaries [#842](https://github.com/RocketPy-Team/RocketPy/pull/842) 

rocketpy/rocket/rocket.py

@@ -384,6 +384,35 @@ def __init__(  # pylint: disable=too-many-statements
         self.prints = _RocketPrints(self)
         self.plots = _RocketPlots(self)
 
+    def _check_missing_components(self):
+        """Check if the rocket is missing any essential components and issue a warning.
+
+        This method verifies whether the rocket has the following key components:
+        - motor
+        - parachute(s)
+        - aerodynamic surface(s)
+
+        If any of these components are missing, a single warning message is issued
+        listing all missing components. This helps users quickly identify potential
+        issues before running simulations or analyses.
+
+        Notes:
+        - The warning uses Python's built-in `warnings.warn` function.
+        """
+        missing_components = []
+        if isinstance(self.motor, EmptyMotor):
+            missing_components.append("motor")
+        if not self.parachutes:
+            missing_components.append("parachutes")
+        if not self.aerodynamic_surfaces or len(self.aerodynamic_surfaces) == 0:
+            missing_components.append("aerodynamic surfaces")
+
+        if missing_components:
+            component_list = ", ".join(missing_components)
+            warnings.warn(
+                f"[WARNING] Rocket has no {component_list} defined.", UserWarning
+            )
+
     @property
     def nosecones(self):
         """A list containing all the nose cones currently added to the rocket."""

tests/unit/test_rocket.py

@@ -10,7 +10,9 @@
 
 
 @patch("matplotlib.pyplot.show")
-def test_elliptical_fins(mock_show, calisto_robust, calisto_trapezoidal_fins):  # pylint: disable=unused-argument
+def test_elliptical_fins(
+    mock_show, calisto_robust, calisto_trapezoidal_fins
+):  # pylint: disable=unused-argument
     test_rocket = calisto_robust
     calisto_robust.aerodynamic_surfaces.remove(calisto_trapezoidal_fins)
     test_rocket.add_elliptical_fins(4, span=0.100, root_chord=0.120, position=-1.168)
@@ -370,6 +372,40 @@ def test_add_motor(calisto_motorless, cesaroni_m1670):
     assert center_of_mass_motorless is not center_of_mass_with_motor
 
 
+def test_check_missing_all_components(calisto_motorless):
+    """Tests the _check_missing_components method for a Rocket with no components."""
+    with pytest.warns(UserWarning) as record:
+        calisto_motorless._check_missing_components()
+
+    assert len(record) == 1
+    msg = str(record[0].message)
+    assert "motor" in msg
+    assert "parachutes" in msg
+    assert "aerodynamic surfaces" in msg
+
+
+def test_check_missing_some_components(calisto):
+    """Tests the _check_missing_components method for a Rocket missing some components."""
+    calisto.parachutes = []
+    calisto.aerodynamic_surfaces = []
+
+    with pytest.warns(UserWarning) as record:
+        calisto._check_missing_components()
+
+    assert len(record) == 1
+    msg = str(record[0].message)
+    assert "parachutes" in msg
+    assert "aerodynamic surfaces" in msg
+
+
+def test_check_missing_no_components_missing(calisto_robust):
+    """Tests the _check_missing_components method for a complete Rocket."""
+    # Call directly — no warnings expected
+    calisto_robust._check_missing_components()
+    # If any warning occurs, pytest will fail automatically
+    assert True
+
+
 def test_set_rail_button(calisto):
     rail_buttons = calisto.set_rail_buttons(0.2, -0.5, 30)
     # assert buttons_distance