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Endpoints defined on the nonterminal either defined as rootNode or being a root, causes a generated, inherited attribute for the handler access to fail.

In case of mqtt, the handler attribute is currently generated using:

  {{#RootTypeComponents}}
  {{#first}}inh MqttServerHandler ASTNode.{{mqttHandlerAttribute}}();{{/first}}
  eq {{rootNodeName}}.get{{name}}().{{mqttHandlerAttribute}}() = {{mqttHandlerField}};
  {{/RootTypeComponents}}
  {{^RootTypeComponents}}
  syn MqttServerHandler {{rootNodeName}}.{{mqttHandlerAttribute}}() = {{mqttHandlerField}};
  {{/RootTypeComponents}}

Here, RootTypeComponents is initialized in RagConnect.toMustache in intermediate/Generation.jadd:

    for (Component child : rootNode.getComponentList()) {
      if (child.isTypeComponent()) {
        result.addRootTypeComponent(child.asTypeComponent().toMustache());
      }
    }

This fails for the example in the documentation, because RootTypeComponents is not empty containing the type component B:

A ::= <Input:String> /<OutputOnA:String>/ B* ;
B ::= /<OutputOnB:String>/ ;