From 89f74c56f4e15b0603c5e8f76cbe4b3c0a1e880a Mon Sep 17 00:00:00 2001
From: Gabriel Belingueres <belingueres@gmail.com>
Date: Sat, 7 Dec 2019 08:41:30 -0300
Subject: [PATCH] Support combine.self="remove"

---
 .../org/codehaus/plexus/util/xml/Xpp3Dom.java | 24 +++++++++++++--
 .../codehaus/plexus/util/xml/Xpp3DomTest.java | 30 +++++++++++++++++++
 2 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/src/main/java/org/codehaus/plexus/util/xml/Xpp3Dom.java b/src/main/java/org/codehaus/plexus/util/xml/Xpp3Dom.java
index 49b25f89..a7026384 100644
--- a/src/main/java/org/codehaus/plexus/util/xml/Xpp3Dom.java
+++ b/src/main/java/org/codehaus/plexus/util/xml/Xpp3Dom.java
@@ -22,7 +22,6 @@
 import java.io.Serializable;
 import java.io.StringWriter;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Iterator;
@@ -76,6 +75,8 @@ public class Xpp3Dom
 
     public static final String SELF_COMBINATION_MERGE = "merge";
 
+    public static final String SELF_COMBINATION_REMOVE = "remove";
+
     /**
      * This default mode for combining a DOM node during merge means that where element names match, the process will
      * try to merge the element attributes and values, rather than overriding the recessive element completely with the
@@ -301,6 +302,13 @@ public void removeChild( int i )
         child.setParent( null );
     }
 
+    public void removeChild( Xpp3Dom child )
+    {
+        childList.remove( child );
+        // In case of any dangling references
+        child.setParent( null );
+    }
+
     // ----------------------------------------------------------------------
     // Parent handling
     // ----------------------------------------------------------------------
@@ -418,7 +426,7 @@ private static void mergeIntoXpp3Dom( Xpp3Dom dominant, Xpp3Dom recessive, Boole
             {
                 for ( String attr : recessive.attributes.keySet() )
                 {
-                    if ( isEmpty( dominant.getAttribute( attr ) ) )
+                    if ( isEmpty( dominant.getAttribute( attr ) ) && !SELF_COMBINATION_MODE_ATTRIBUTE.equals( attr ) )
                     {
                         dominant.setAttribute( attr, recessive.getAttribute( attr ) );
                     }
@@ -489,7 +497,17 @@ private static void mergeIntoXpp3Dom( Xpp3Dom dominant, Xpp3Dom recessive, Boole
                         else if ( it.hasNext() )
                         {
                             Xpp3Dom dominantChild = it.next();
-                            mergeIntoXpp3Dom( dominantChild, recessiveChild, childMergeOverride );
+
+                            String dominantChildCombinationMode =
+                                dominantChild.getAttribute( SELF_COMBINATION_MODE_ATTRIBUTE );
+                            if ( SELF_COMBINATION_REMOVE.equals( dominantChildCombinationMode ) )
+                            {
+                                dominant.removeChild( dominantChild );
+                            }
+                            else
+                            {
+                                mergeIntoXpp3Dom( dominantChild, recessiveChild, childMergeOverride );
+                            }
                         }
                     }
                 }
diff --git a/src/test/java/org/codehaus/plexus/util/xml/Xpp3DomTest.java b/src/test/java/org/codehaus/plexus/util/xml/Xpp3DomTest.java
index 04444f31..35fb5590 100644
--- a/src/test/java/org/codehaus/plexus/util/xml/Xpp3DomTest.java
+++ b/src/test/java/org/codehaus/plexus/util/xml/Xpp3DomTest.java
@@ -329,6 +329,36 @@ public void testDupeChildren()
         assertEquals( "y", dom.getChild( "foo" ).getValue() );
     }
 
+    @Test
+    public void testShouldRemoveEntireElementWithAttributesAndChildren()
+        throws Exception
+    {
+        String dominantStr = "<config><service combine.self=\"remove\"/></config>";
+        String recessiveStr = "<config><service><parameter>parameter</parameter></service></config>";
+        Xpp3Dom dominantConfig = Xpp3DomBuilder.build( new StringReader( dominantStr ) );
+        Xpp3Dom recessiveConfig = Xpp3DomBuilder.build( new StringReader( recessiveStr ) );
+
+        Xpp3Dom result = Xpp3Dom.mergeXpp3Dom( dominantConfig, recessiveConfig );
+
+        assertEquals( 0, result.getChildCount() );
+        assertEquals( "config", result.getName() );
+    }
+
+    @Test
+    public void testShouldRemoveDoNotRemoveTagWhenSwappedInputDOMs()
+        throws Exception
+    {
+        String dominantStr = "<config><service combine.self=\"remove\"/></config>";
+        String recessiveStr = "<config><service><parameter>parameter</parameter></service></config>";
+        Xpp3Dom dominantConfig = Xpp3DomBuilder.build( new StringReader( dominantStr ) );
+        Xpp3Dom recessiveConfig = Xpp3DomBuilder.build( new StringReader( recessiveStr ) );
+
+        // same DOMs as testShouldRemoveEntireElementWithAttributesAndChildren(), swapping dominant <--> recessive
+        Xpp3Dom result = Xpp3Dom.mergeXpp3Dom( recessiveConfig, dominantConfig );
+
+        assertEquals( recessiveConfig.toString(), result.toString() );
+    }
+
     private static class FixedInputLocationBuilder
         implements Xpp3DomBuilder.InputLocationBuilder
     {