Index: src/java/org/apache/ivy/plugins/parser/xml/XmlModuleDescriptorUpdater.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- src/java/org/apache/ivy/plugins/parser/xml/XmlModuleDescriptorUpdater.java	(revision 1471573)
+++ src/java/org/apache/ivy/plugins/parser/xml/XmlModuleDescriptorUpdater.java	(revision )
@@ -27,17 +27,7 @@
 import java.io.PrintWriter;
 import java.io.StringWriter;
 import java.net.URL;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.Date;
-import java.util.Iterator;
-import java.util.LinkedHashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.Stack;
-import java.util.StringTokenizer;
+import java.util.*;
 
 import javax.xml.parsers.ParserConfigurationException;
 
@@ -296,6 +286,20 @@
                 //by an absolute path. 
                 includeStarted(attributes);
             } else if ("ivy-module/info/extends".equals(path)) {
+                if (options.isMerge()) {
+                    ModuleDescriptor mergedDescriptor = options.getMergedDescriptor();
+                    ExtendsDescriptor[] inheritedDescriptors = mergedDescriptor.getInheritedDescriptors();
+                    for (int i = 0; i < inheritedDescriptors.length; i++) {
+                        ExtendsDescriptor inheritedDescriptor = inheritedDescriptors[i];
+                        ModuleDescriptor rprid = inheritedDescriptor.getParentMd();
+                        if (rprid instanceof DefaultModuleDescriptor) {
+                            DefaultModuleDescriptor defaultModuleDescriptor = (DefaultModuleDescriptor) rprid;
+                            if (defaultModuleDescriptor.getDefaultConfMapping() != null) {
+                                defaultConfMapping = defaultModuleDescriptor.getDefaultConfMapping();
+                            }
+                        }
+                    }
+                }
                 startExtends(attributes);
             } else if ("ivy-module/dependencies/dependency".equals(path)) {
                 startElementInDependency(attributes);
@@ -1048,6 +1052,12 @@
         private void writeInheritedConfigurations(ModuleDescriptor merged) {
             if (!mergedConfigurations) {
                 mergedConfigurations = true;
+//                Map<String, String> attributes = new HashMap<String, String>();
+//                if (merged instanceof DefaultModuleDescriptor) {
+//                    DefaultModuleDescriptor defaultModuleDescriptor = (DefaultModuleDescriptor) merged;
+//                    String defaultConfMapping1 = defaultModuleDescriptor.getDefaultConfMapping();
+//                    attributes.put("defaultconfmapping", defaultConfMapping)
+//                }
                 writeInheritedItems(merged, merged.getConfigurations(),
                     ConfigurationPrinter.INSTANCE, "configurations", false);
             }
Index: test/java/org/apache/ivy/plugins/parser/xml/XmlModuleUpdaterTest.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- test/java/org/apache/ivy/plugins/parser/xml/XmlModuleUpdaterTest.java	(revision 1471573)
+++ test/java/org/apache/ivy/plugins/parser/xml/XmlModuleUpdaterTest.java	(revision )
@@ -356,6 +356,32 @@
             + XmlModuleDescriptorUpdater.LINE_SEPARATOR) != -1);
     }
 
+    //IVY-1420
+    public void testMergedUpdateWithExtendsAndDefaultConfMappings() throws Exception {
+        URL url = XmlModuleUpdaterTest.class.getResource("test-extends-configurations-defaultconfmapping.xml");
+
+        XmlModuleDescriptorParser parser = XmlModuleDescriptorParser.getInstance();
+        ModuleDescriptor md = parser.parseDescriptor(new IvySettings(), url, true);
+
+        ByteArrayOutputStream buffer = new ByteArrayOutputStream();
+        XmlModuleDescriptorUpdater.update(url, buffer,
+                getUpdateOptions("release", "mynewrev")
+                        .setMerge(true)
+                        .setMergedDescriptor(md));
+
+        ModuleDescriptor updatedMd = parser.parseDescriptor(new IvySettings(),
+                new ByteArrayInputStream(buffer.toByteArray()), new BasicResource("test", false, 0, 0,
+                false), true);
+
+        Configuration[] configurations = updatedMd.getConfigurations();
+        assertNotNull("Configurations shouldn't be null", configurations);
+        assertEquals("Number of configurations is incorrect", 3, configurations.length);
+
+        String updatedXml = buffer.toString();
+        System.out.println(updatedXml);
+        assertTrue(updatedXml.indexOf("defaultconfmapping=\"conf1,default->@()\"") != -1);
+    }
+
     private UpdateOptions getUpdateOptions(String status, String revision) {
         return getUpdateOptions(new IvySettings(), new HashMap(), status, revision, new Date());
     }
Index: test/java/org/apache/ivy/plugins/parser/xml/test-extends-configurations-defaultconfmapping.xml
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- test/java/org/apache/ivy/plugins/parser/xml/test-extends-configurations-defaultconfmapping.xml	(revision )
+++ test/java/org/apache/ivy/plugins/parser/xml/test-extends-configurations-defaultconfmapping.xml	(revision )
@@ -0,0 +1,33 @@
+<!--
+   Licensed to the Apache Software Foundation (ASF) under one
+   or more contributor license agreements.  See the NOTICE file
+   distributed with this work for additional information
+   regarding copyright ownership.  The ASF licenses this file
+   to you under the Apache License, Version 2.0 (the
+   "License"); you may not use this file except in compliance
+   with the License.  You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing,
+   software distributed under the License is distributed on an
+   "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+   KIND, either express or implied.  See the License for the
+   specific language governing permissions and limitations
+   under the License.    
+-->
+<ivy-module version="1.0">
+	<info organisation="myorg"
+	       module="mymodule"
+	       status="integration"
+	       publication="20091206000000">
+	       <extends organisation="myorg" module="myparentwithconfmapping" revision="latest.revision"
+	       			location="test-extends-parent-defaultconfmapping.xml" extendType="configurations"/>
+	</info>
+	<configurations>
+		<conf name="conf2" visibility="private"/>
+	</configurations>
+	<dependencies>
+		<dependency name="mymodule2" rev="2.0" conf="conf1,conf2"/>
+	</dependencies>
+</ivy-module>
Index: test/java/org/apache/ivy/plugins/parser/xml/test-extends-parent-defaultconfmapping.xml
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- test/java/org/apache/ivy/plugins/parser/xml/test-extends-parent-defaultconfmapping.xml	(revision )
+++ test/java/org/apache/ivy/plugins/parser/xml/test-extends-parent-defaultconfmapping.xml	(revision )
@@ -0,0 +1,34 @@
+<!--
+   Licensed to the Apache Software Foundation (ASF) under one
+   or more contributor license agreements.  See the NOTICE file
+   distributed with this work for additional information
+   regarding copyright ownership.  The ASF licenses this file
+   to you under the Apache License, Version 2.0 (the
+   "License"); you may not use this file except in compliance
+   with the License.  You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing,
+   software distributed under the License is distributed on an
+   "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+   KIND, either express or implied.  See the License for the
+   specific language governing permissions and limitations
+   under the License.    
+-->
+<ivy-module version="1.0">
+	<info organisation="myorg"
+	       module="myparentwithconfmapping"
+	       revision="myrev"
+	       status="integration"
+	       publication="20091206000000">
+	       <description>Parent module description.  </description>
+	</info>
+	<configurations defaultconfmapping="conf1,default->@()">
+		<conf name="default"/>
+		<conf name="conf1" visibility="public"/>
+	</configurations>
+	<dependencies>
+		<dependency name="mymodule1" rev="1.0" conf="default"/>
+	</dependencies>
+</ivy-module>