[460923] Do not filter FeatureMapChanges on removed Elements

The DefaultDiffEngine tries to minimize the number of calculated
differences. This fix modifies the DefaultDiffEngine to allow
calculation of FeatureMapChanges on removed elements. This is needed to
prevent ordering issues when contained elements are added back via
right-to-left merges.

Includes testcase.

Signed-off-by: Stefan Dirix <sdirix@eclipsesource.com>
Change-Id: Ia119ed2bf98a2730aa74c343e9138ed4bd82d35e

4 files changed, 77 insertions, 2 deletions

diff --git a/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/merge/MultipleMergeTest.java b/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/merge/MultipleMergeTest.java
index 302dcc9ed..ef9e1aced 100644
--- a/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/merge/MultipleMergeTest.java
+++ b/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/merge/MultipleMergeTest.java
@@ -7,7 +7,7 @@
  * 
  * Contributors:
  *     Obeo - initial API and implementation
- *     Stefan Dirix - bugs 441172, 452147 and 460902
+ *     Stefan Dirix - bugs 441172, 452147, 460902 and 460923
  *******************************************************************************/
 package org.eclipse.emf.compare.tests.merge;
 
@@ -29,9 +29,11 @@ import static org.junit.Assert.assertTrue;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterators;
+import com.google.common.collect.Lists;
 
 import java.io.IOException;
 import java.util.Collections;
+import java.util.Iterator;
 import java.util.List;
 
 import org.eclipse.emf.common.util.BasicMonitor;
@@ -1357,6 +1359,49 @@ public class MultipleMergeTest {
 	}
 
 	@Test
+	public void testRemoveFeatureMapR2L() throws IOException {
+		ResourceSetImpl resourceSet = new ResourceSetImpl();
+
+		final Resource left = twoWayInput.getRemoveFeatureMapR2LLeft(resourceSet);
+		final Resource right = twoWayInput.getRemoveFeatureMapR2LRight(resourceSet);
+
+		final IComparisonScope scope = new DefaultComparisonScope(left, right, null);
+		Comparison comparison = EMFCompare.builder().build().compare(scope);
+
+		final List<Diff> differences = comparison.getDifferences();
+
+		// There should be 5 differences
+		// 1. Remove first key (ReferenceChange)
+		// 2. Remove first key (FeatureMapChange)
+		// 3. Remove second key (ReferenceChange)
+		// 4. Remove second key (FeatureMapChange)
+		// 5. Remove NodeFeatureMapContainment (ReferenceChange)
+		assertEquals(5, comparison.getDifferences().size());
+
+		// Also test dependencies by merging the FeatureMapChanges first
+		Iterator<Diff> featureMapChangesIt = Iterators.filter(differences.iterator(),
+				instanceOf(FeatureMapChange.class));
+		List<Diff> featureMapChanges = Lists.newArrayList(featureMapChangesIt);
+		assertEquals(2, featureMapChanges.size());
+
+		// Execute FeatureMapChanges first to test if they properly resolve their dependencies
+		for (Diff diff : featureMapChanges) {
+			mergerRegistry.getHighestRankingMerger(diff).copyRightToLeft(diff, new BasicMonitor());
+		}
+
+		// Execute the remaining differences
+		for (Diff diff : differences) {
+			if (!featureMapChanges.contains(diff)) {
+				mergerRegistry.getHighestRankingMerger(diff).copyRightToLeft(diff, new BasicMonitor());
+			}
+		}
+
+		// Check if no differences are left
+		comparison = EMFCompare.builder().build().compare(scope);
+		assertEquals(0, comparison.getDifferences().size());
+	}
+
+	@Test
 	public void testMergeAllDiffsTwice() throws IOException {
 		final IdentifierMatchInputData inputData = new IdentifierMatchInputData();
 		final Resource left = inputData.getExtlibraryLeft();
diff --git a/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/merge/data/TwoWayMergeInputData.java b/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/merge/data/TwoWayMergeInputData.java
index cba60de1c..5f84f8abb 100644
--- a/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/merge/data/TwoWayMergeInputData.java
+++ b/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/merge/data/TwoWayMergeInputData.java
@@ -8,7 +8,7 @@
  * Contributors:
  *     Philip Langer - initial API and implementation
  *     Alexandra Buzila - test data for bug 446252
- *     Stefan Dirix - test data for bugs 452147, 453749 and 460902
+ *     Stefan Dirix - test data for bugs 452147, 453749, 460902 and 460923
  *******************************************************************************/
 package org.eclipse.emf.compare.tests.merge.data;
 
@@ -115,4 +115,12 @@ public class TwoWayMergeInputData extends AbstractInputData {
 	public Resource getFeatureMapDependencyL2RRight(ResourceSet resourceSet) throws IOException {
 		return loadFromClassLoader("twoway/featuremapdependency/ltr/right.nodes", resourceSet);
 	}
+
+	public Resource getRemoveFeatureMapR2LLeft(ResourceSet resourceSet) throws IOException {
+		return loadFromClassLoader("twoway/removefeaturemap/rtl/left.nodes", resourceSet);
+	}
+
+	public Resource getRemoveFeatureMapR2LRight(ResourceSet resourceSet) throws IOException {
+		return loadFromClassLoader("twoway/removefeaturemap/rtl/right.nodes", resourceSet);
+	}
 }
diff --git a/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/merge/data/twoway/removefeaturemap/rtl/left.nodes b/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/merge/data/twoway/removefeaturemap/rtl/left.nodes
new file mode 100644
index 000000000..41499d0dd
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/merge/data/twoway/removefeaturemap/rtl/left.nodes
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="ASCII"?>
+<nodes:Node
+    xmi:version="2.0"
+    xmlns:xmi="http://www.omg.org/XMI"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns:nodes="http://www.eclipse.org/emf/compare/tests/nodes"
+    xmi:id="_root"
+    name="Root">
+</nodes:Node>
diff --git a/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/merge/data/twoway/removefeaturemap/rtl/right.nodes b/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/merge/data/twoway/removefeaturemap/rtl/right.nodes
new file mode 100644
index 000000000..2662fdac6
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/merge/data/twoway/removefeaturemap/rtl/right.nodes
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="ASCII"?>
+<nodes:Node
+    xmi:version="2.0"
+    xmlns:xmi="http://www.omg.org/XMI"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns:nodes="http://www.eclipse.org/emf/compare/tests/nodes"
+    xmi:id="_root"
+    name="Root">
+    <containmentRef1 xsi:type="nodes:NodeFeatureMapContainment" name="n">
+      <secondKey/>
+      <firstKey/>
+    </containmentRef1>
+</nodes:Node>