fixed #128

Author: mgeipel

src/main/java/org/culturegraph/mf/morph/functions/Regexp.java

@@ -50,8 +50,8 @@ public void receive(final String name, final String value, final NamedValueSourc
 			while (matcher.find()) {
 				populateVars();
 				if (!tempVars.isEmpty()) {
-					getNamedValueReceiver().receive(name,
-							StringUtil.format(format, tempVars), source, recordCount, entityCount);
+					getNamedValueReceiver().receive(name, StringUtil.format(format, tempVars), source, recordCount,
+							entityCount);
 				}
 			}
 		}
@@ -60,8 +60,9 @@ public void receive(final String name, final String value, final NamedValueSourc
 	private void populateVars() {
 		tempVars.clear();
 		for (int i = 0; i <= matcher.groupCount(); ++i) {
-			if (!matcher.group(i).isEmpty()) {
-				tempVars.put(String.valueOf(i), matcher.group(i));
+			final String group = matcher.group(i);
+			if (group != null && !group.isEmpty()) {
+				tempVars.put(String.valueOf(i), group);
 			}
 		}
 	}

src/test/java/org/culturegraph/mf/morph/functions/Regexp.xml

@@ -2,6 +2,7 @@
 <metamorph-test version="1.0"
 	xmlns="http://www.culturegraph.org/metamorph-test" xmlns:cgxml="http://www.culturegraph.org/cgxml"
 	xmlns:mm="http://www.culturegraph.org/metamorph">
+
 	<test-case name="Regexp function">
 		<input type="text/x-cg+xml">
 			<cgxml:cgxml version="1.0">
@@ -21,7 +22,7 @@
 						<mm:regexp match=".*" format="resource:P${0}" />
 					</mm:data>
 					<mm:data source="001." name="subject">
-						<mm:regexp match=".*" format="${1}"/>
+						<mm:regexp match=".*" format="${1}" />
 					</mm:data>
 					<mm:data source="001." name="subject">
 						<mm:regexp match=".*" />
@@ -41,4 +42,39 @@
 			</cgxml:cgxml>
 		</result>
 	</test-case>
+
+
+	<test-case name="empty match group">
+		<input type="text/x-cg+xml">
+			<cgxml:cgxml version="1.0">
+				<cgxml:records>
+					<cgxml:record id="1">
+
+						<cgxml:literal name="s" value="aaccdd" />
+						<cgxml:literal name="s" value="ax" />
+					</cgxml:record>
+				</cgxml:records>
+			</cgxml:cgxml>
+		</input>
+		<transformation type="text/x-metamorph+xml">
+			<mm:metamorph version="1">
+				<mm:rules>
+					<mm:data source="s">
+						<mm:regexp match="aa(bb*)?(cc*)(dd*)" format="${1}${2}${3}" />
+					</mm:data>
+
+				</mm:rules>
+			</mm:metamorph>
+		</transformation>
+		<result type="text/x-cg+xml">
+			<cgxml:cgxml version="1.0">
+				<cgxml:records>
+					<cgxml:record id="1">
+						<cgxml:literal name="s" value="ccdd" />
+					</cgxml:record>
+				</cgxml:records>
+			</cgxml:cgxml>
+		</result>
+	</test-case>
+
 </metamorph-test>