Feature Model: Added check for uniqueness of feature names

Feature names are now checked to be unique among all literals.

Issue-ref: 4278
Issue-URL: af3#4278

Signed-off-by: Andreas Bayha <bayha@fortiss.org>

org.fortiss.variability/src/org/fortiss/variability/util/.ratings

 FeatureModelTransformationUtils.java b38702296dcb48ff311b382bb9c05d2590e2dfac GREEN
 Pair.java 2dfd7dc65f7b9ba09a120f1a6058d1e8e9556a37 GREEN
-VariabilityUtils.java 66a727bdb58715dc7b1bd0ce320bd647f374f7d6 GREEN
+VariabilityUtils.java 281b8512cdcbdf0494a752562460c9894cbe24e5 YELLOW
 VariabilityUtilsInternal.java 9c781a47513bb0c4ddcd13be1c27d62b70f25998 GREEN

org.fortiss.variability/src/org/fortiss/variability/util/VariabilityUtils.java

@@ -17,6 +17,7 @@ package org.fortiss.variability.util;
 
 import static java.util.stream.Collectors.toList;
 import static org.fortiss.variability.model.VariabilityModelElementFactory.createFeatureConfigurationForFeature;
+import static org.fortiss.variability.util.VariabilityUtilsInternal.getAllElementsFromSameContainmentTree;
 import static org.fortiss.variability.util.VariabilityUtilsInternal.getAllReferences;
 import static org.fortiss.variability.util.VariabilityUtilsInternal.getParentsWithType;
 
@@ -27,6 +28,7 @@ import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
 import org.eclipse.emf.common.util.EList;
+import org.eclipse.emf.ecore.EObject;
 import org.fortiss.variability.model.features.AbstractCompositionalFeature;
 import org.fortiss.variability.model.features.AbstractCrossFeatureConstraint;
 import org.fortiss.variability.model.features.AbstractFeature;
@@ -192,4 +194,22 @@ public class VariabilityUtils {
 		features.removeAll(getParentsWithType(constraint, AbstractFeature.class));
 		return features;
 	}
+
+	/**
+	 * Retrieves all literals with the given name from the whole containment tree in which 'context'
+	 * is contained in.
+	 * 
+	 * Note, that the resulting {@link List} should usually contain at most one literal, as literal
+	 * names should be unique.
+	 * 
+	 * @param context
+	 *            Any {@link EObject} in the containment tree to search in.
+	 * @param name
+	 *            The name of the literal which is searched.
+	 * @return A {@link List} of all literals with the given name.
+	 */
+	public static List<ILiteralReferencable> getLiteralsWithName(EObject context, String name) {
+		return getAllElementsFromSameContainmentTree(context, ILiteralReferencable.class).stream()
+				.filter(l -> l.getName().equals(name)).collect(toList());
+	}
 }