prevent segfault whan empty sequence passet to GasState::mix_rats setter (#308)

Author: slayoo

src/gas_state.hpp

@@ -117,8 +117,13 @@ struct GasState {
     }
 
     static void set_mix_rats(const GasState &self, const nlohmann::json &json) {
+        if (json.size() == 0)
+            throw std::runtime_error("Non-empty sequence of mixing ratios expected");
+
         GimmickGuard<InputGimmick> guard(json);
-        f_gas_state_from_json(self.ptr.f_arg(),
-             self.gas_data->ptr.f_arg());
+        f_gas_state_from_json(
+            self.ptr.f_arg(),
+            self.gas_data->ptr.f_arg()
+        );
     }
 };

tests/test_gas_state.py

@@ -130,3 +130,16 @@ def test_set_mix_rats_from_json():
         for i_spec in range(gas_data.n_spec):
             if not i_spec in idx_set:
                 assert sut[i_spec] == 0
+
+    @staticmethod
+    def test_set_mix_rats_empty():
+        # arrange
+        gas_data = ppmc.GasData(("SO2",))
+        sut = ppmc.GasState(gas_data)
+
+        # act
+        with pytest.raises(RuntimeError) as excinfo:
+            sut.mix_rats = ()
+
+        # assert
+        assert str(excinfo.value) == "Non-empty sequence of mixing ratios expected"