NullPointerException if ecore file contains attribute with name 'default'

[rsoika]

I have a Strange NullPointerException in my project caused by a ecore element definition with the name 'default'

  <eClassifiers xsi:type="ecore:EClass" name="ExclusiveGateway" eSuperTypes="#//Gateway">
    <eAnnotations source="http:///org/eclipse/emf/ecore/util/ExtendedMetaData">
      <details key="name" value="tExclusiveGateway"/>
      <details key="kind" value="elementOnly"/>
    </eAnnotations>
    <eStructuralFeatures xsi:type="ecore:EReference" name="default" ordered="false"
        eType="#//SequenceFlow" resolveProxies="false">
      <eAnnotations source="http:///org/eclipse/emf/ecore/util/ExtendedMetaData">
        <details key="kind" value="attribute"/>
        <details key="name" value="default"/>
        <details key="namespace" value="http://www.omg.org/spec/BPMN/20100524/MODEL"/>
      </eAnnotations>
    </eStructuralFeatures>
  </eClassifiers>

The generation of my ecore model classes is all fine and also my GLSP Server part with the AbstractGNodeBuilder has no problem.

public class GatewayNodeBuilder extends AbstractGNodeBuilder<ExclusiveGateway, GatewayNodeBuilder> {

    private final String name;
    private final String gatewayType;

    public GatewayNodeBuilder(final String type, final String name, String gatewayType) {
        super(type);
        this.name = name;
        if (gatewayType == null || gatewayType.isEmpty()) {
            gatewayType = "";
        }
        this.gatewayType = gatewayType;
    }
    @Override
    protected ExclusiveGateway instantiate() {
        return BpmngraphFactory.eINSTANCE.createExclusiveGateway();
    }
    @Override
    protected GatewayNodeBuilder self() {
        return this;
    }
    @Override
    protected void setProperties(final ExclusiveGateway node) {
        super.setProperties(node);
        node.setName(name);
        node.getCategory().add(gatewayType);
        node.setLayout(GConstants.Layout.FREEFORM);

        node.getChildren().add(BPMNBuilderHelper.createCompartmentHeader(node));
        node.getChildren().add(BPMNBuilderHelper.createBPMNPort(node, -30.0, 0.0, 60.0, 60.0));
    }
}

But when I try to add this element into my model the server part throws the following exception:

WARNUNG: Failed to send notification message.
java.lang.NullPointerException
	at org.eclipse.emf.ecore.impl.BasicEObjectImpl.eDerivedStructuralFeatureID(BasicEObjectImpl.java:1536)
	at org.eclipse.emf.ecore.impl.BasicEObjectImpl.eIsSet(BasicEObjectImpl.java:1277)
	at org.eclipse.glsp.graph.gson.GModelElementTypeAdapter.isSet(GModelElementTypeAdapter.java:185)
	at org.eclipse.glsp.graph.gson.GModelElementTypeAdapter.writeProperties(GModelElementTypeAdapter.java:171)
	at org.eclipse.glsp.graph.gson.GModelElementTypeAdapter.write(GModelElementTypeAdapter.java:111)
	at org.eclipse.glsp.graph.gson.GModelElementTypeAdapter.write(GModelElementTypeAdapter.java:44)
	at org.eclipse.lsp4j.jsonrpc.json.adapters.CollectionTypeAdapter.write(CollectionTypeAdapter.java:139)
	at org.eclipse.lsp4j.jsonrpc.json.adapters.CollectionTypeAdapter.write(CollectionTypeAdapter.java:40)
	at com.google.gson.Gson.toJson(Gson.java:669)
	at org.eclipse.glsp.graph.gson.PropertyBasedTypeAdapter.writeProperty(PropertyBasedTypeAdapter.java:221)
	at org.eclipse.glsp.graph.gson.GModelElementTypeAdapter.writeProperties(GModelElementTypeAdapter.java:174)
	at org.eclipse.glsp.graph.gson.GModelElementTypeAdapter.writeProperties(GModelElementTypeAdapter.java:180)
	at org.eclipse.glsp.graph.gson.GModelElementTypeAdapter.write(GModelElementTypeAdapter.java:111)
	at org.eclipse.glsp.graph.gson.GModelElementTypeAdapter.write(GModelElementTypeAdapter.java:44)
	at com.google.gson.Gson.toJson(Gson.java:669)
	at org.eclipse.glsp.graph.gson.PropertyBasedTypeAdapter.writeProperty(PropertyBasedTypeAdapter.java:221)
	at org.eclipse.glsp.graph.gson.PropertyBasedTypeAdapter.writeProperties(PropertyBasedTypeAdapter.java:202)
	at org.eclipse.glsp.graph.gson.PropertyBasedTypeAdapter.write(PropertyBasedTypeAdapter.java:185)
	at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:69)
	at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:125)
	at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:243)
	at com.google.gson.Gson.toJson(Gson.java:669)
	at org.eclipse.lsp4j.jsonrpc.json.adapters.MessageTypeAdapter.write(MessageTypeAdapter.java:434)
	at org.eclipse.lsp4j.jsonrpc.json.adapters.MessageTypeAdapter.write(MessageTypeAdapter.java:55)
	at com.google.gson.Gson.toJson(Gson.java:669)
	at com.google.gson.Gson.toJson(Gson.java:648)
	at org.eclipse.lsp4j.jsonrpc.json.MessageJsonHandler.serialize(MessageJsonHandler.java:145)
	at org.eclipse.lsp4j.jsonrpc.json.MessageJsonHandler.serialize(MessageJsonHandler.java:140)
	at org.eclipse.lsp4j.jsonrpc.json.StreamMessageConsumer.consume(StreamMessageConsumer.java:59)
	at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint.notify(RemoteEndpoint.java:126)
	at org.eclipse.lsp4j.jsonrpc.services.EndpointProxy.invoke(EndpointProxy.java:88)
	at com.sun.proxy.$Proxy25.process(Unknown Source)
	at org.eclipse.glsp.server.actions.ClientActionHandler.send(ClientActionHandler.java:58)
	at org.eclipse.glsp.server.actions.ClientActionHandler.execute(ClientActionHandler.java:52)
	at org.eclipse.glsp.server.internal.actions.DefaultActionDispatcher.runAction(DefaultActionDispatcher.java:191)
	at org.eclipse.glsp.server.internal.actions.DefaultActionDispatcher.handleAction(DefaultActionDispatcher.java:170)
	at org.eclipse.glsp.server.internal.actions.DefaultActionDispatcher.dispatch(DefaultActionDispatcher.java:100)
	at org.eclipse.glsp.server.actions.ActionDispatcher.lambda$dispatchAll$0(ActionDispatcher.java:47)
	at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195)
	at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1655)
	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
	at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:913)
	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:578)
	at org.eclipse.glsp.server.actions.ActionDispatcher.dispatchAll(ActionDispatcher.java:47)
	at org.eclipse.glsp.server.internal.actions.DefaultActionDispatcher.runAction(DefaultActionDispatcher.java:194)
	at org.eclipse.glsp.server.internal.actions.DefaultActionDispatcher.handleAction(DefaultActionDispatcher.java:170)
	at org.eclipse.glsp.server.internal.actions.DefaultActionDispatcher.handleNextAction(DefaultActionDispatcher.java:157)
	at org.eclipse.glsp.server.internal.actions.DefaultActionDispatcher.runThread(DefaultActionDispatcher.java:144)
	at java.base/java.lang.Thread.run(Thread.java:829)

I am not sure but maybe this exception may be raised from com.google.gson.Gson

After a lot of research I found out, that the name of my ecore:EReference 'default' is the problem. If I rename the reference to something like 'defaultflow' everything works again fine.