FeatureModel: Added check for empty feature name to editor

Empty Strings are no longer accepted in the feature editor.

Issue-ref: 4257
Issue-URL: af3#4257

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

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

-VariabilityUtils.java ccbcc8a13557a107608130e25880f9523b84cfba GREEN
+VariabilityUtils.java 7b423cb9f0e267ecb42c74c6fe8d2a23c1f6bf06 YELLOW

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

@@ -18,6 +18,8 @@ package org.fortiss.tooling.ext.variability.util;
 import static org.fortiss.tooling.ext.variability.model.VariabilityModelElementFactory.createOptionalVariationPointSpecification;
 import static org.fortiss.tooling.kernel.utils.EcoreUtils.getFirstChildWithType;
 import static org.fortiss.tooling.kernel.utils.EcoreUtils.pickFirstInstanceOf;
+import static org.fortiss.variability.util.VariabilityUtils.FEATURE_LITERAL_LEGAL_CHAR_REGEX;
+import static org.fortiss.variability.util.VariabilityUtils.PRESENCE_CONDITIONS_KEYWORDS;
 
 import org.eclipse.emf.ecore.EObject;
 import org.fortiss.tooling.base.model.element.IModelElement;
@@ -35,6 +37,12 @@ import org.fortiss.variability.presence.compiler.PresenceConditionCompiler;
  */
 public class VariabilityUtils {
 
+	/** Failure message for incorrect Feature names. */
+	public final static String FEATURE_NAME_ERROR_MSG = "Feature names may only contain " +
+			FEATURE_LITERAL_LEGAL_CHAR_REGEX.replaceAll("\\\\", "") +
+			", must not be empty and must be different from the keywords " +
+			PRESENCE_CONDITIONS_KEYWORDS.replaceAll("\\|", ", ") + ".";
+
 	/**
 	 * Checks for the given {@link EObject} whether it has been deactivated by a
 	 * {@link DeactivationSpecification}.