Prevent insertion of particles with negative mass (espressomd#4679)

Description of changes:
- particles can no longer be created or updated with a negative mass or a null mass

src/python/espressomd/particle_data.pyx

@@ -378,6 +378,8 @@ cdef class ParticleHandle:
             IF MASS == 1:
                 check_type_or_throw_except(
                     _mass, 1, float, "Mass has to be 1 float")
+                if _mass <= 0.:
+                    raise ValueError("mass must be a float > 0")
                 set_particle_mass(self._id, _mass)
             ELSE:
                 raise AttributeError("You are trying to set the particle mass "

testsuite/python/particle.py

@@ -358,6 +358,36 @@ def test_invalid_particle_creation(self):
         with self.assertRaisesRegex(ValueError, err_msg):
             self.system.part.add([1, 2])
 
+    def test_invalid_particle_attributes(self):
+        p = self.partcl
+        with self.assertRaisesRegex(ValueError, "type must be an integer >= 0"):
+            p.type = -1
+        with self.assertRaisesRegex(ValueError, "mol_id must be an integer >= 0"):
+            p.mol_id = -1
+        if espressomd.has_features("ENGINE"):
+            with self.assertRaisesRegex(Exception, "You can't set v_swim and f_swim at the same time"):
+                p.swimming = {"v_swim": 0.3, "f_swim": 0.6}
+            with self.assertRaisesRegex(Exception, "'mode' has to be either 'pusher', 'puller' or 'N/A'"):
+                p.swimming = {"v_swim": 0.3, "mode": "invalid"}
+        if espressomd.has_features("MASS"):
+            for mass in [0., -1., -2.]:
+                with self.assertRaisesRegex(ValueError, "mass must be a float > 0"):
+                    p.mass = mass
+
+    def test_missing_features(self):
+        def check(feature, prop, throwing_values, valid_value=None):
+            if not espressomd.has_features(feature):
+                if valid_value is not None:
+                    # this should not throw
+                    setattr(self.partcl, prop, valid_value)
+                for throwing_value in throwing_values:
+                    with self.assertRaisesRegex(RuntimeError, f"Feature {feature} not compiled in"):
+                        setattr(self.partcl, prop, throwing_value)
+
+        check("MASS", "mass", [1.1, 0., -1.], 1.)
+        check("ELECTROSTATICS", "q", [1., -1.], 0.)
+        check("VIRTUAL_SITES", "virtual", [True], False)
+
     def test_parallel_property_setters(self):
         s = self.system
         s.part.clear()