Component :
    "component" name = ID "{"
    (ports+=Port)*
    "}";

Port :
    "port" dir=Direction name=ID ":"  ref=[Interface|ID] ";"
    ;

enum Direction :
    IN="in" | OUT="out";

Instance:
    "instance" name=ID ":" type=[Component|ID] ";"
    ;

Connection:
    "connect" in=[Instance|ID]"."p=[Port|ID] "->" in2=[Instance|ID]"."p2=[Port|ID] ";"
    ;

The default code completion will traverse all defined Ports for the references p and p2 in the Connection rule. A better behaviour would be:

• Show only the ports in the instances (in, in2)
• For p, show only “OUT”-Ports, for p2, show only “IN”-ports.

To do this, we need to define methods in a class derived from AbstractDeclarativeScopeProvider. The method names follow the signature scope_<rule>_<element>, so the the old code fragment for was:

public class AutomotiveDSLScopeProvider extends AbstractDeclarativeScopeProvider {

    IScope scope_Connection_p2(Connection ctx, EReference ref)

    {

        if(ctx.getIn2() == null )

            return IScope.NULLSCOPE;

        else

            return new SimpleScope(IScope.NULLSCOPE, getRPorts(ctx.getIn2().getType()));

    }

    IScope scope_Connection_p(Connection ctx, EReference ref)

    {

        if(ctx.getIn() == null )

            return IScope.NULLSCOPE;

        else

            return new SimpleScope(IScope.NULLSCOPE, getPPorts(ctx.getIn().getType()));

    }

    private Iterable<IScopedElement> getPPorts(Component clazz) {

        List<IScopedElement> result = new ArrayList<IScopedElement>();

        for (Port f : clazz.getPorts())

            if (f instanceof Port && f.getDir() == Direction.OUT)

                result.add(ScopedElement.create(f.getName(), f,"("));

        return result;

    }

    private Iterable<IScopedElement> getRPorts(Component clazz) {

        List<IScopedElement> result = new ArrayList<IScopedElement>();

        for (Port f : clazz.getPorts())

            if (f instanceof Port && f.getDir() == Direction.IN)

                result.add(ScopedElement.create(f.getName(), f));

        return result;

    }

}

One of the important changes that I use different imports, because some are deprecated and some are generally nice to use. Newly introduced are:

import static org.eclipse.xtext.scoping.Scopes.*;

for helpful functions and

import com.google.common.base.Predicate;
import com.google.common.collect.Iterables;
import com.google.inject.Inject;

for working with lists. So the new code looks like this:

public class AutomotiveDSLScopeProvider extends AbstractDeclarativeScopeProvider {

	protected Predicate<Port> pPortPred = new Predicate<Port>(){
		public boolean  apply(Port input) { return input.getDir() == Direction.OUT ; }
	};

	protected Predicate<Port> rPortPred = new Predicate<Port>(){
		public boolean  apply(Port input) { return input.getDir() == Direction.IN ; }
	};

	public IScope scope_Connection_p2(Connection ctx, EReference eRef)
	{
		EList<Port> features = ctx.getIn2().getType().getPorts();
		return scopeFor(Iterables.filter(features,rPortPred));
	}

	public IScope scope_Connection_p(Connection ctx, EReference eRef)
	{
		EList<Port> features = ctx.getIn2().getType().getPorts();
		return scopeFor(Iterables.filter(features,pPortPred));
	}

}

Note that the scopeFor helper takes away the work of creating the newly introduced IEObjectDescription that I struggled with at first. Once you know how, migrating seems not too bad.