[Simulation] Trigger error when Node already contains component

Sofa/framework/Simulation/Core/src/sofa/simulation/Node.cpp

@@ -1024,8 +1024,25 @@ void Node::setSleeping(bool val)
     }
 }
 
+template<class LinkType, class Component>
+void checkAlreadyContains(Node& self, LinkType& link, Component* obj)
+{
+    if constexpr (!LinkType::IsMultiLink)
+    {
+        if (link != obj && link != nullptr)
+        {
+            static const auto componentClassName = Component::GetClass()->className;
+            msg_error(&self) << "Trying to add a " << componentClassName << " ('" << obj->getName() << "' " << obj << ")"
+                << " into the Node '" << self.getPathName()
+                << "', whereas it already contains one ('" << link->getName() << "' " << link.get() << ")."
+                << " Only one " << componentClassName << " is permitted in a Node. The previous "
+                << componentClassName << " is replaced and the behavior is undefined.";
+        }
+    }
+}
+
 #define NODE_DEFINE_SEQUENCE_ACCESSOR( CLASSNAME, FUNCTIONNAME, SEQUENCENAME ) \
-    void Node::add##FUNCTIONNAME( CLASSNAME* obj ) { SEQUENCENAME.add(obj); } \
+    void Node::add##FUNCTIONNAME( CLASSNAME* obj ) { checkAlreadyContains(*this, SEQUENCENAME, obj); SEQUENCENAME.add(obj); } \
     void Node::remove##FUNCTIONNAME( CLASSNAME* obj ) { SEQUENCENAME.remove(obj); }
 
 NODE_DEFINE_SEQUENCE_ACCESSOR( sofa::core::behavior::BaseAnimationLoop, AnimationLoop, animationManager )

Sofa/framework/Simulation/Graph/test/Node_test.cpp

@@ -19,6 +19,8 @@
 *                                                                             *
 * Contact information: [email protected]                             *
 ******************************************************************************/
+#include <sofa/core/behavior/BaseMechanicalState.h>
+#include <sofa/simulation/MechanicalVisitor.h>
 #include <sofa/testing/BaseSimulationTest.h>
 using sofa::testing::BaseSimulationTest ;
 
@@ -33,6 +35,9 @@ namespace sofa
 
 TEST( Node_test, getPathName)
 {
+    // required to be able to use EXPECT_MSG_NOEMIT and EXPECT_MSG_EMIT
+    sofa::helper::logging::MessageDispatcher::addHandler(sofa::testing::MainGtestMessageHandler::getInstance() ) ;
+
     /* create trivial DAG :
      *
      * A
@@ -90,6 +95,9 @@ TEST(Node_test, addObjectAtFront)
 
 TEST(Node_test, addObjectPreventingSharedContext)
 {
+    // required to be able to use EXPECT_MSG_NOEMIT and EXPECT_MSG_EMIT
+    sofa::helper::logging::MessageDispatcher::addHandler(sofa::testing::MainGtestMessageHandler::getInstance() ) ;
+
     const sofa::core::sptr<Node> root = sofa::simpleapi::createNode("root");
 
     const BaseObject::SPtr A = core::objectmodel::New<Dummy>("A");
@@ -177,6 +185,53 @@ TEST(Node_test, getObjectsStdUnorderedSet)
     EXPECT_NE(objects.find(B.get()), objects.end());
 }
 
+class CounterVisitor : public simulation::MechanicalVisitor
+{
+public:
+    using MechanicalVisitor::MechanicalVisitor;
+
+    Result fwdMechanicalState(simulation::Node* node, sofa::core::behavior::BaseMechanicalState* state) override
+    {
+        SOFA_UNUSED(node);
+        SOFA_UNUSED(state);
+        m_counter++;
+        return Result::RESULT_CONTINUE;
+    }
+
+    Result fwdMappedMechanicalState(simulation::Node* node, sofa::core::behavior::BaseMechanicalState* state) override
+    {
+        SOFA_UNUSED(node);
+        SOFA_UNUSED(state);
+        ++m_counter;
+        return Result::RESULT_CONTINUE;
+    }
+
+    std::size_t m_counter = 0;
+};
+
+TEST(Node_test, twoMechanicalStatesInTheSameNode)
+{
+    // required to be able to use EXPECT_MSG_NOEMIT and EXPECT_MSG_EMIT
+    sofa::helper::logging::MessageDispatcher::addHandler(sofa::testing::MainGtestMessageHandler::getInstance() ) ;
+
+    const sofa::core::sptr<Node> root = sofa::simpleapi::createNode("root");
+
+    const auto plugins = testing::makeScopedPlugin({Sofa.Component.StateContainer});
+    sofa::simpleapi::createObject(root, "MechanicalObject", {{"template", "Vec3"}, {"name", "A"}});
+
+    EXPECT_MSG_EMIT(Error);
+    sofa::simpleapi::createObject(root, "MechanicalObject", {{"template", "Vec3"}, {"name", "B"}});
+
+    //the last added state is the one in Node
+    EXPECT_EQ(root->mechanicalState->getName(), "B");
+
+    CounterVisitor visitor(core::MechanicalParams::defaultInstance());
+    root->executeVisitor(&visitor);
+
+    //only one of the two added states is visited
+    EXPECT_EQ(visitor.m_counter, 1);
+}
+
 }// namespace sofa
 
 

Sofa/framework/Simulation/Graph/test/Simulation_test.cpp

@@ -223,10 +223,9 @@ struct Scene_test: public NumericTest<SReal>
         root = simulation::getSimulation()->createNewGraph("root");
         root->addObject(core::objectmodel::New<InstrumentedObject<MechanicalObject3> >());
 
-        typename UniformMass3::SPtr uniformMass = core::objectmodel::New<UniformMass3>();
+        typename UniformMass3::SPtr uniformMass = core::objectmodel::New<InstrumentedObject<UniformMass3>>();
         uniformMass->d_totalMass.setValue(1.0);
         root->addObject(uniformMass);
-        root->addObject(core::objectmodel::New<InstrumentedObject<UniformMass3> >());
 
         const simulation::Node::SPtr child  = simulation::getSimulation()->createNewNode("child");
         root->addChild(child);