[471456] Have SessionEditorInput override URIEditorInput.equals()

- Have SessionEditorInput override URIEditorInput.equals() to not open
Sirius editor which don't corresponds to a specified DRepresentation
when using xpath based URI fragment.
- Update also SiriusMatchingStrategy to leave responsibility of
IEditorInput matching test to IEditorInput.equals() method.
- Deprecate SessionEditorInput.dispose() as a IEditorInput can be reused
by
several IEditorPart instance with the NavigationHistory feature. To
avoid memory leak on SessionEditorInput fields, we use WeakReference.
- Update Release Notes about SessionEditorInput.getInput()/dispose()
methods.
- Add SessionEditorInputTests.
- Avoid "One modeling project is invalid" message with
SaveWhenNoEditorsTests.
- Avoid NPE on VisibilityPostCommitListener asyncExec with
EntitiesDiagramHideRevealTests.

Bug: 471456
Change-Id: Iaff308d54cfb76f77e47c3f09d3cb3fecaf1cbca
Signed-off-by: Esteban Dugueperoux <esteban.dugueperoux@obeo.fr>

12 files changed, 260 insertions, 164 deletions

diff --git a/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/ui/part/SiriusMatchingStrategy.java b/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/ui/part/SiriusMatchingStrategy.java
index 11a4163a4e..9b8f552cd0 100644
--- a/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/ui/part/SiriusMatchingStrategy.java
+++ b/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/ui/part/SiriusMatchingStrategy.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2007, 2009 THALES GLOBAL SERVICES.
+ * Copyright (c) 2007, 2015 THALES GLOBAL SERVICES.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -25,6 +25,7 @@ public class SiriusMatchingStrategy implements IEditorMatchingStrategy {
     /**
      * @was-generated
      */
+    @Override
     public boolean matches(IEditorReference editorRef, IEditorInput input) {
         IEditorInput editorInput;
         try {
@@ -39,13 +40,8 @@ public class SiriusMatchingStrategy implements IEditorMatchingStrategy {
         if (editorInput.equals(input)) {
             return true;
         }
-        if (editorInput instanceof URIEditorInput && input instanceof URIEditorInput) {
-            return ((URIEditorInput) editorInput).getURI().equals(((URIEditorInput) input).getURI());
-        }
+        // Manage FileEditorInput to support Sirius editor opening from a marker
         if (input instanceof FileEditorInput && editorInput instanceof URIEditorInput) {
-            // Check if the file is the same
-            // CDO Bridge for Sirius : uriEditorPath can be null,
-            // as the URI is a cdo URI
             String uriEditorInputPath = ((URIEditorInput) editorInput).getURI().toPlatformString(false);
             String fileEditorInputPath = ((FileEditorInput) input).getFile().getFullPath().toString();
             return ((uriEditorInputPath != null) && (fileEditorInputPath != null) && (uriEditorInputPath.equals(fileEditorInputPath)));
diff --git a/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/ui/tools/internal/editor/DDiagramEditorImpl.java b/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/ui/tools/internal/editor/DDiagramEditorImpl.java
index 3689530f2b..2e33159c20 100644
--- a/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/ui/tools/internal/editor/DDiagramEditorImpl.java
+++ b/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/ui/tools/internal/editor/DDiagramEditorImpl.java
@@ -470,6 +470,9 @@ public class DDiagramEditorImpl extends SiriusDiagramEditor implements DDiagramE
     }
 
     private IEditorInput getCorrectedInput(IEditorInput input) {
+        // input is a FileEditorInput in case editor is opened from a marker
+        // then we don't have yet uriFragment to gmf Diagram, we will get it
+        // when gotoMarker() method will be called
         if (input instanceof FileEditorInput) {
             IFile file = ((FileEditorInput) input).getFile();
             URI analysisURI = URI.createPlatformResourceURI("/" + file.getProject().getName() + "/" + file.getProjectRelativePath(), true);
@@ -740,12 +743,6 @@ public class DDiagramEditorImpl extends SiriusDiagramEditor implements DDiagramE
             }
             sGViewer = null;
         }
-
-        // Dispose the session editor input to keep the minimum information to
-        // be restore from the INavigationHistory and EditorHistory.
-        if (getEditorInput() instanceof SessionEditorInput) {
-            ((SessionEditorInput) getEditorInput()).dispose();
-        }
         IUndoContext savedUndoContext = getUndoContext();
         // to avoid dispose of current session related IUndoeableOperation
         setUndoContext(new UndoContext());
diff --git a/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/ui/tools/internal/marker/SiriusMarkerNavigationProviderSpec.java b/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/ui/tools/internal/marker/SiriusMarkerNavigationProviderSpec.java
index 9eca37f988..820ad00467 100644
--- a/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/ui/tools/internal/marker/SiriusMarkerNavigationProviderSpec.java
+++ b/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/ui/tools/internal/marker/SiriusMarkerNavigationProviderSpec.java
@@ -27,6 +27,7 @@ import org.eclipse.sirius.business.api.session.SessionManager;
 import org.eclipse.sirius.diagram.DDiagram;
 import org.eclipse.sirius.diagram.DSemanticDiagram;
 import org.eclipse.sirius.diagram.DiagramPlugin;
+import org.eclipse.sirius.diagram.business.api.query.EObjectQuery;
 import org.eclipse.sirius.diagram.ui.internal.providers.SiriusMarkerNavigationProvider;
 import org.eclipse.sirius.diagram.ui.part.SiriusDiagramEditor;
 import org.eclipse.sirius.diagram.ui.part.SiriusDiagramEditorUtil;
@@ -34,6 +35,7 @@ import org.eclipse.sirius.diagram.ui.tools.api.editor.DDiagramEditor;
 import org.eclipse.sirius.diagram.ui.tools.internal.resource.NavigationMarkerConstants;
 import org.eclipse.sirius.ui.business.api.dialect.DialectEditor;
 import org.eclipse.sirius.ui.business.api.dialect.DialectUIManager;
+import org.eclipse.sirius.ui.business.api.session.SessionEditorInput;
 import org.eclipse.sirius.ui.tools.internal.views.common.modelingproject.OpenRepresentationsFileJob;
 import org.eclipse.sirius.viewpoint.description.validation.ValidationRule;
 import org.eclipse.ui.IEditorReference;
@@ -94,12 +96,19 @@ public class SiriusMarkerNavigationProviderSpec extends SiriusMarkerNavigationPr
         if (defaultEditor.getDiagram().equals(markerDiagram)) {
             targetEditor = defaultEditor;
         } else {
-            final URIEditorInput editorInput = new URIEditorInput(markerDiagramURI, SiriusMarkerNavigationProviderSpec.resolveSemanticElement(markerDiagram).getName());
+            URIEditorInput editorInput = null;
+            String editorName = SiriusMarkerNavigationProviderSpec.resolveSemanticElement(markerDiagram).getName();
+            Session session = new EObjectQuery(markerDiagram).getSession();
+            if (session != null) {
+                editorInput = new SessionEditorInput(markerDiagramURI, editorName, session);
+            } else {
+                editorInput = new URIEditorInput(markerDiagramURI, editorName);
+            }
             final SiriusDiagramEditor searchEditor = searchEditor(editorInput);
             if (searchEditor != null) {
                 targetEditor = searchEditor;
             } else {
-                Session session = getOrOpenTargetSession(sessionResourceUri);
+                session = getOrOpenTargetSession(sessionResourceUri);
 
                 // Open the corresponding editor
                 SiriusDiagramEditor openedEditor = null;
@@ -137,8 +146,8 @@ public class SiriusMarkerNavigationProviderSpec extends SiriusMarkerNavigationPr
     }
 
     /**
-     * Search a {@link SiriusDiagramEditor} with the <code>editorInput</code>
-     * in the opened editors.
+     * Search a {@link SiriusDiagramEditor} with the <code>editorInput</code> in
+     * the opened editors.
      * 
      * @param editorInput
      *            The editorInput to find.
@@ -183,7 +192,8 @@ public class SiriusMarkerNavigationProviderSpec extends SiriusMarkerNavigationPr
      *            defined by the platform.
      * @return The added marker.
      */
-    public static IMarker addMarker(final IFile file, final String elementId, final String diagramURI, final String semanticURI, final String location, final String message, final int statusSeverity) {
+    public static IMarker addMarker(final IFile file, final String elementId, final String diagramURI, final String semanticURI, final String location, final String message,
+            final int statusSeverity) {
         final IMarker marker = SiriusMarkerNavigationProvider.addMarker(file, elementId, location, message, statusSeverity);
         try {
             marker.setAttribute(NavigationMarkerConstants.DIAGRAM_URI, diagramURI);
diff --git a/plugins/org.eclipse.sirius.doc/doc/Release_Notes.html b/plugins/org.eclipse.sirius.doc/doc/Release_Notes.html
index 2c9cc4b88d..1b284b1185 100644
--- a/plugins/org.eclipse.sirius.doc/doc/Release_Notes.html
+++ b/plugins/org.eclipse.sirius.doc/doc/Release_Notes.html
@@ -93,6 +93,20 @@
 				<code>IUndoableCommand</code> because useless since undo/redo is managed by EMF Transaction.
 			</li>
 		</ul>
+		<h4 id="Changesinorg.eclipse.sirius.ui">Changes in 
+			<code>org.eclipse.sirius.ui</code>
+		</h4>
+		<ul>
+			<li>
+				<code>org.eclipse.sirius.ui.business.api.session.SessionEditorInput.dispose()</code> method has been deprecated as a 
+				<code>IEditorInput</code> can be reused by several instances of 
+				<code>IEditorPart</code> through the navigation history view.
+			</li>
+			<li>
+				<code>org.eclipse.sirius.ui.business.api.session.SessionEditorInput.getInput()</code> method has been added to get the real input for a 
+				<code>DRepresentation</code>.
+			</li>
+		</ul>
 		<h4 id="Changesinorg.eclipse.sirius.tests.swtbot.support">Changes in 
 			<code>org.eclipse.sirius.tests.swtbot.support</code>
 		</h4>
@@ -556,7 +570,7 @@
 				<code>org.eclipse.sirius.viewpoint.DContainer</code> has been removed.
 			</li>
 		</ul>
-		<h4 id="Changesinorg.eclipse.sirius.ui">Changes in 
+		<h4 id="Changesinorg.eclipse.sirius.ui2">Changes in 
 			<code>org.eclipse.sirius.ui</code>
 		</h4>
 		<ul>
@@ -1206,7 +1220,7 @@
 				<code>org.eclipse.gmf.runtime.emf.core.util.CrossReferenceAdapter</code>. However considering the way Sirius uses GMF, this adapter is not needed.
 			</li>
 		</ul>
-		<h4 id="Changesinorg.eclipse.sirius.ui2">Changes in 
+		<h4 id="Changesinorg.eclipse.sirius.ui3">Changes in 
 			<code>org.eclipse.sirius.ui</code>
 		</h4>
 		<ul>
@@ -1494,4 +1508,4 @@
 			</li>
 		</ul>
 	</body>
-</html>
+</html>
\ No newline at end of file
diff --git a/plugins/org.eclipse.sirius.doc/doc/Release_Notes.textile b/plugins/org.eclipse.sirius.doc/doc/Release_Notes.textile
index c651e7772c..be0321a27b 100644
--- a/plugins/org.eclipse.sirius.doc/doc/Release_Notes.textile
+++ b/plugins/org.eclipse.sirius.doc/doc/Release_Notes.textile
@@ -23,6 +23,11 @@ h4. Changes in @org.eclipse.sirius@
 * @org.eclipse.sirius.tools.api.command.IUndoableCommand@ interface removed because it is useless since undo/redo is managed by EMF Transaction.
 * @org.eclipse.sirius.tools.api.command.DCommand@ no more inherits of @IUndoableCommand@ because useless since undo/redo is managed by EMF Transaction.
 
+h4. Changes in @org.eclipse.sirius.ui@
+
+* @org.eclipse.sirius.ui.business.api.session.SessionEditorInput.dispose()@ method has been deprecated as a @IEditorInput@ can be reused by several instances of @IEditorPart@ through the navigation history view.
+* @org.eclipse.sirius.ui.business.api.session.SessionEditorInput.getInput()@ method has been added to get the real input for a @DRepresentation@.
+
 h4. Changes in @org.eclipse.sirius.tests.swtbot.support@
 
 * <span class="label label-success">Added</span> The methods @closePerspective(String)@, @closeSiriusPerspective()@ and @closeModelingPerspective()@ have been added in class @org.eclipse.sirius.tests.swtbot.support.api.perspective.DesignerPerspectives@ to allow the closing of perspectives.
diff --git a/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/suite/common/AllCommonPluginTests.java b/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/suite/common/AllCommonPluginTests.java
index b91555f588..76bbfa5a5b 100644
--- a/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/suite/common/AllCommonPluginTests.java
+++ b/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/suite/common/AllCommonPluginTests.java
@@ -41,6 +41,7 @@ import org.eclipse.sirius.tests.unit.api.session.DAnalysisSessionTests;
 import org.eclipse.sirius.tests.unit.api.session.OpenSessionTest;
 import org.eclipse.sirius.tests.unit.api.session.ReloadSessionTest;
 import org.eclipse.sirius.tests.unit.api.session.SampleSessionTest;
+import org.eclipse.sirius.tests.unit.api.session.SessionEditorInputTests;
 import org.eclipse.sirius.tests.unit.api.session.SessionManagerListener2Tests;
 import org.eclipse.sirius.tests.unit.api.session.SessionSemanticResourceTests;
 import org.eclipse.sirius.tests.unit.api.session.SessionServiceTest;
@@ -226,6 +227,7 @@ public class AllCommonPluginTests extends TestCase {
 
         suite.addTestSuite(DAnalysisSessionTests.class);
         suite.addTestSuite(SampleSessionTest.class);
+        suite.addTestSuite(SessionEditorInputTests.class);
         suite.addTestSuite(SiriusRegistryTests.class);
         suite.addTestSuite(SiriusRegistryListener2Tests.class);
         suite.addTestSuite(SessionSemanticResourceTests.class);
diff --git a/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/unit/api/modelingproject/SaveWhenNoEditorsTests.java b/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/unit/api/modelingproject/SaveWhenNoEditorsTests.java
index 00c4745b2d..1de9c4f7ed 100644
--- a/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/unit/api/modelingproject/SaveWhenNoEditorsTests.java
+++ b/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/unit/api/modelingproject/SaveWhenNoEditorsTests.java
@@ -47,7 +47,6 @@ public class SaveWhenNoEditorsTests extends SiriusDiagramTestCase implements Eco
 
     @Override
     protected void setUp() throws Exception {
-        super.createModelingProject = true;
         super.setUp();
 
         changePlatformUIPreference(IWorkbenchPreferenceConstants.PROMPT_WHEN_SAVEABLE_STILL_OPEN, true);
diff --git a/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/unit/api/session/SessionEditorInputTests.java b/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/unit/api/session/SessionEditorInputTests.java
new file mode 100644
index 0000000000..dad2f38b95
--- /dev/null
+++ b/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/unit/api/session/SessionEditorInputTests.java
@@ -0,0 +1,137 @@
+/*******************************************************************************
+ * Copyright (c) 2015 Obeo.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *    Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.sirius.tests.unit.api.session;
+
+import java.util.Collection;
+import java.util.Collections;
+
+import org.eclipse.core.runtime.NullProgressMonitor;
+import org.eclipse.emf.common.command.Command;
+import org.eclipse.emf.common.command.CommandStack;
+import org.eclipse.emf.common.util.URI;
+import org.eclipse.emf.ecore.EcoreFactory;
+import org.eclipse.emf.ecore.resource.Resource;
+import org.eclipse.emf.ecore.resource.impl.ResourceSetImpl;
+import org.eclipse.emf.ecore.util.EcoreUtil;
+import org.eclipse.emf.edit.command.MoveCommand;
+import org.eclipse.emf.transaction.TransactionalEditingDomain;
+import org.eclipse.sirius.business.api.componentization.ViewpointRegistry;
+import org.eclipse.sirius.business.api.dialect.DialectManager;
+import org.eclipse.sirius.business.api.dialect.command.CopyRepresentationCommand;
+import org.eclipse.sirius.business.api.query.URIQuery;
+import org.eclipse.sirius.business.api.session.Session;
+import org.eclipse.sirius.business.api.session.factory.SessionFactory;
+import org.eclipse.sirius.common.ui.tools.api.util.EclipseUIUtil;
+import org.eclipse.sirius.tests.support.api.TestsUtil;
+import org.eclipse.sirius.tools.api.command.semantic.AddSemanticResourceCommand;
+import org.eclipse.sirius.ui.business.api.dialect.DialectUIManager;
+import org.eclipse.sirius.ui.business.api.viewpoint.ViewpointSelectionCallback;
+import org.eclipse.sirius.ui.business.internal.commands.ChangeViewpointSelectionCommand;
+import org.eclipse.sirius.viewpoint.DAnalysis;
+import org.eclipse.sirius.viewpoint.DRepresentation;
+import org.eclipse.sirius.viewpoint.DView;
+import org.eclipse.sirius.viewpoint.ViewpointPackage;
+import org.eclipse.sirius.viewpoint.description.Viewpoint;
+import org.eclipse.ui.IEditorPart;
+
+import junit.framework.TestCase;
+
+/**
+ * Tests about https://bugs.eclipse.org/bugs/show_bug.cgi?id=471456.
+ * 
+ * @author <a href="mailto:esteban.dugueperoux@obeo.fr">Esteban Dugueperoux</a>
+ */
+public class SessionEditorInputTests extends TestCase {
+
+    private static final String TEMPORARY_PROJECT_NAME = "DesignerTestProject";
+
+    private static final String SESSION_MODEL_FILENAME = "My.aird";
+
+    private static final String SEMANTIC_MODEL_FILENAME = "My.ecore";
+
+    private Session session;
+
+    private DView dView;
+
+    private DRepresentation dRepresentation1;
+
+    private DRepresentation dRepresentation2;
+
+    @Override
+    public void setUp() throws Exception {
+        super.setUp();
+        URI sessionResourceURI = URI.createURI(URIQuery.INMEMORY_URI_SCHEME + ":/" + TEMPORARY_PROJECT_NAME + "/" + SESSION_MODEL_FILENAME);
+        session = SessionFactory.INSTANCE.createSession(sessionResourceURI, new NullProgressMonitor());
+        session.open(new NullProgressMonitor());
+        URI semanticResourceURI = URI.createURI(URIQuery.INMEMORY_URI_SCHEME + ":/" + TEMPORARY_PROJECT_NAME + "/" + SEMANTIC_MODEL_FILENAME);
+        Resource semanticResource = new ResourceSetImpl().createResource(semanticResourceURI);
+        semanticResource.getContents().add(EcoreFactory.eINSTANCE.createEPackage());
+        semanticResource.save(Collections.emptyMap());
+        Command addSemanticResourceCmd = new AddSemanticResourceCommand(session, semanticResourceURI, new NullProgressMonitor());
+        TransactionalEditingDomain domain = session.getTransactionalEditingDomain();
+        CommandStack commandStack = domain.getCommandStack();
+        commandStack.execute(addSemanticResourceCmd);
+        URI designViewpointURI = URI.createURI("viewpoint:/org.eclipse.sirius.sample.ecore.design/Design");
+        Viewpoint viewpoint = ViewpointRegistry.getInstance().getViewpoint(designViewpointURI);
+        viewpoint = (Viewpoint) session.getTransactionalEditingDomain().getResourceSet().getEObject(EcoreUtil.getURI(viewpoint), true);
+        commandStack.execute(
+                new ChangeViewpointSelectionCommand(session, new ViewpointSelectionCallback(), Collections.singleton(viewpoint), Collections.<Viewpoint> emptySet(), new NullProgressMonitor()));
+        Collection<DRepresentation> allRepresentations = DialectManager.INSTANCE.getAllRepresentations(session);
+        commandStack.execute(new CopyRepresentationCommand(domain, allRepresentations, "copy", session));
+        DAnalysis dAnalysis = (DAnalysis) session.getSessionResource().getContents().get(0);
+        dView = dAnalysis.getOwnedViews().get(0);
+        dRepresentation1 = dView.getOwnedRepresentations().get(0);
+        dRepresentation2 = dView.getOwnedRepresentations().get(1);
+        session.save(new NullProgressMonitor());
+    }
+
+    /**
+     * Test that opening a {@link DRepresentation} whose {@link URI} has changed
+     * to be same a already opened {@link DRepresentation} doesn't open the
+     * already opened {@link DRepresentation} but a new editor for the requested
+     * {@link DRepresentation}.
+     */
+    public void testSessionEditorInputWithInputURIChange() {
+        IEditorPart editor1 = DialectUIManager.INSTANCE.openEditor(session, dRepresentation1, new NullProgressMonitor());
+        TestsUtil.synchronizationWithUIThread();
+        IEditorPart editor2 = DialectUIManager.INSTANCE.openEditor(session, dRepresentation2, new NullProgressMonitor());
+        TestsUtil.synchronizationWithUIThread();
+        assertEquals(2, EclipseUIUtil.getActivePage().getEditorReferences().length);
+        DialectUIManager.INSTANCE.closeEditor(editor1, false);
+        TestsUtil.synchronizationWithUIThread();
+        assertEquals(1, EclipseUIUtil.getActivePage().getEditorReferences().length);
+        // Change URI of DRepresentations by changing order as uriFragments are
+        // xpath based
+        URI dRepresentation1URI = EcoreUtil.getURI(dRepresentation1);
+        URI dRepresentation2URI = EcoreUtil.getURI(dRepresentation2);
+        Command moveCmd = MoveCommand.create(session.getTransactionalEditingDomain(), dView, ViewpointPackage.Literals.DVIEW__OWNED_REPRESENTATIONS, dRepresentation2, 0);
+        session.getTransactionalEditingDomain().getCommandStack().execute(moveCmd);
+        String assertMessage = "DRepresentation's URI should have changed as they are stored in a InMemoryResourceImpl with xpath based uriFragment";
+        assertEquals(assertMessage, dRepresentation1URI, EcoreUtil.getURI(dRepresentation2));
+        assertEquals(assertMessage, dRepresentation2URI, EcoreUtil.getURI(dRepresentation1));
+        IEditorPart newEditor = DialectUIManager.INSTANCE.openEditor(session, dRepresentation1, new NullProgressMonitor());
+        assertNotSame(editor1, newEditor);
+        assertEquals("Editor for representation1 should be opened", 2, EclipseUIUtil.getActivePage().getEditorReferences().length);
+        DialectUIManager.INSTANCE.closeEditor(editor1, false);
+        DialectUIManager.INSTANCE.closeEditor(editor2, false);
+        TestsUtil.synchronizationWithUIThread();
+    }
+
+    @Override
+    public void tearDown() throws Exception {
+        dRepresentation2 = null;
+        dRepresentation1 = null;
+        dView = null;
+        session.close(new NullProgressMonitor());
+        session = null;
+        super.tearDown();
+    }
+}
diff --git a/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/unit/diagram/action/EntitiesDiagramHideRevealTests.java b/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/unit/diagram/action/EntitiesDiagramHideRevealTests.java
index 8a2c0c6454..f3da8cc8ea 100644
--- a/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/unit/diagram/action/EntitiesDiagramHideRevealTests.java
+++ b/plugins/org.eclipse.sirius.tests.junit/src/org/eclipse/sirius/tests/unit/diagram/action/EntitiesDiagramHideRevealTests.java
@@ -39,7 +39,6 @@ import org.eclipse.sirius.tests.support.api.EclipseTestsSupportHelper;
 import org.eclipse.sirius.tests.support.api.SiriusDiagramTestCase;
 import org.eclipse.sirius.tests.support.api.TestsUtil;
 import org.eclipse.sirius.tests.unit.diagram.modeler.ecore.EcoreModeler;
-import org.eclipse.sirius.tools.api.command.SiriusCommand;
 import org.eclipse.sirius.ui.business.api.dialect.DialectUIManager;
 import org.eclipse.sirius.viewpoint.DRepresentation;
 import org.eclipse.ui.IEditorPart;
@@ -424,7 +423,7 @@ public class EntitiesDiagramHideRevealTests extends SiriusDiagramTestCase implem
      *            the new visibility for this element
      */
     protected void changeDiagramElementVisiblity(final DDiagramElement element, final boolean newVisibility) {
-        session.getTransactionalEditingDomain().getCommandStack().execute(new SiriusCommand(session.getTransactionalEditingDomain()) {
+        session.getTransactionalEditingDomain().getCommandStack().execute(new RecordingCommand(session.getTransactionalEditingDomain()) {
             @Override
             protected void doExecute() {
                 if (newVisibility) {
@@ -434,6 +433,7 @@ public class EntitiesDiagramHideRevealTests extends SiriusDiagramTestCase implem
                 }
             }
         });
+        TestsUtil.synchronizationWithUIThread();
     }
 
     private int getNbVisibleDiagramElements(final DDiagram diagram) {
diff --git a/plugins/org.eclipse.sirius.ui/src/org/eclipse/sirius/ui/business/api/session/SessionEditorInput.java b/plugins/org.eclipse.sirius.ui/src/org/eclipse/sirius/ui/business/api/session/SessionEditorInput.java
index 703c78cd17..55abd31708 100644
--- a/plugins/org.eclipse.sirius.ui/src/org/eclipse/sirius/ui/business/api/session/SessionEditorInput.java
+++ b/plugins/org.eclipse.sirius.ui/src/org/eclipse/sirius/ui/business/api/session/SessionEditorInput.java
@@ -10,6 +10,8 @@
  *******************************************************************************/
 package org.eclipse.sirius.ui.business.api.session;
 
+import java.lang.ref.WeakReference;
+
 import org.eclipse.core.resources.IFile;
 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.NullProgressMonitor;
@@ -17,6 +19,7 @@ import org.eclipse.core.runtime.OperationCanceledException;
 import org.eclipse.emf.common.EMFPlugin;
 import org.eclipse.emf.common.ui.URIEditorInput;
 import org.eclipse.emf.common.util.URI;
+import org.eclipse.emf.ecore.EObject;
 import org.eclipse.emf.ecore.resource.Resource;
 import org.eclipse.sirius.business.api.session.Session;
 import org.eclipse.sirius.business.api.session.SessionManager;
@@ -45,7 +48,7 @@ public class SessionEditorInput extends URIEditorInput {
      */
     private static final String DEFAULT_EDITOR_NAME = "Representation";
 
-    private Session session;
+    private WeakReference<Session> sessionRef;
 
     /**
      * add a name field to override the {@link URIEditorInput} one's with
@@ -55,6 +58,8 @@ public class SessionEditorInput extends URIEditorInput {
 
     private URI sessionResourceURI;
 
+    private WeakReference<EObject> inputRef;
+
     /**
      * Create a new SessionEditorInput with the current session and ui session.
      * 
@@ -68,7 +73,7 @@ public class SessionEditorInput extends URIEditorInput {
     public SessionEditorInput(final URI uri, final String name, final Session session) {
         super(uri, name);
         this.name = name;
-        this.session = session;
+        this.sessionRef = new WeakReference<Session>(session);
         if (session.getSessionResource() != null) {
             this.sessionResourceURI = session.getSessionResource().getURI();
         }
@@ -91,23 +96,38 @@ public class SessionEditorInput extends URIEditorInput {
      * @return the model editing session.
      */
     public Session getSession() {
+        Session session = sessionRef != null ? sessionRef.get() : null;
         if (session == null) {
-            // It will probably be clean during the dispose, so recreate it from
-            // URI.
             URI sessionModelURI = getURI().trimFragment();
             if (sessionResourceURI != null) {
                 sessionModelURI = sessionResourceURI;
             }
             session = getSession(sessionModelURI);
+            if (session != null) {
+                this.sessionRef = new WeakReference<Session>(session);
+            }
         }
         return session;
     }
 
     /**
-     * {@inheritDoc}
+     * Get the input of this editor input.
      * 
-     * @see org.eclipse.emf.common.ui.URIEditorInput#getName()
+     * @return the input of this editor input
      */
+    public EObject getInput() {
+        EObject input = inputRef != null ? inputRef.get() : null;
+        if (input == null) {
+            if (getSession() != null && getSession().isOpen() && getURI().hasFragment()) {
+                input = getSession().getTransactionalEditingDomain().getResourceSet().getEObject(getURI(), false);
+                if (input != null) {
+                    inputRef = new WeakReference<EObject>(input);
+                }
+            }
+        }
+        return input;
+    }
+
     @Override
     public String getName() {
         return name == null ? super.getName() : name;
@@ -121,9 +141,6 @@ public class SessionEditorInput extends URIEditorInput {
         this.name = string;
     }
 
-    /**
-     * {@inheritDoc}
-     */
     @Override
     public void saveState(final IMemento memento) {
         super.saveState(memento);
@@ -134,9 +151,6 @@ public class SessionEditorInput extends URIEditorInput {
         }
     }
 
-    /**
-     * {@inheritDoc}
-     */
     @Override
     protected void loadState(final IMemento memento) {
         super.loadState(memento);
@@ -144,7 +158,10 @@ public class SessionEditorInput extends URIEditorInput {
         final String sessionResourceURIString = memento.getString(SESSION_RESOURCE_URI);
         if (sessionResourceURIString != null) {
             sessionResourceURI = URI.createURI(sessionResourceURIString);
-            session = getSession(sessionResourceURI);
+            Session newSession = getSession(sessionResourceURI);
+            if (newSession != null) {
+                this.sessionRef = new WeakReference<Session>(newSession);
+            }
         }
     }
 
@@ -172,7 +189,7 @@ public class SessionEditorInput extends URIEditorInput {
             sessionFromURI = null;
             // Silent catch: can happen if failing to retrieve the session from
             // its URI
-        }  catch (OperationCanceledException e) {
+        } catch (OperationCanceledException e) {
             sessionFromURI = null;
             // Silent catch: can happen if failing to retrieve the session from
             // its URI
@@ -180,17 +197,11 @@ public class SessionEditorInput extends URIEditorInput {
         return sessionFromURI;
     }
 
-    /**
-     * {@inheritDoc}
-     */
     @Override
     protected String getBundleSymbolicName() {
         return SiriusEditPlugin.getPlugin().getSymbolicName();
     }
 
-    /**
-     * {@inheritDoc}
-     */
     @Override
     public String getFactoryId() {
         return SessionEditorInputFactory.ID;
@@ -201,7 +212,7 @@ public class SessionEditorInput extends URIEditorInput {
      * 
      * @param sessionResourceURI
      *            a session Resource URI.
-     * @return a new Sessioneditorinput.
+     * @return a new SessionEditorinput.
      * 
      * @since 0.9.0
      */
@@ -215,9 +226,6 @@ public class SessionEditorInput extends URIEditorInput {
         return new SessionEditorInput(sessionResourceURI, DEFAULT_EDITOR_NAME, session);
     }
 
-    /**
-     * {@inheritDoc}
-     */
     @Override
     public String getToolTipText() {
         return getURI().trimFragment().toString() + "/" + getName();
@@ -230,9 +238,13 @@ public class SessionEditorInput extends URIEditorInput {
      * org.eclipse.ui.internal.EditorHistory. This method must not be called by
      * client, it is automatically called by the dispose of
      * {@link DDiagramEditor}.
+     * 
+     * @deprecated since a {@link org.eclipse.ui.IEditorInput} can be reused by
+     *             several instances of {@link org.eclipse.ui.IEditorPart}
+     *             through the navigation history view.
      */
+    @Deprecated
     public void dispose() {
-        session = null;
     }
 
     /**
@@ -249,9 +261,9 @@ public class SessionEditorInput extends URIEditorInput {
     @Override
     public boolean exists() {
         boolean exists = super.exists();
-        if (!exists && session != null) {
+        if (!exists && getSession() != null) {
             URI resourceURI = getURI().trimFragment();
-            for (Resource resource : session.getAllSessionResources()) {
+            for (Resource resource : getSession().getAllSessionResources()) {
                 if (resource.getURI().equals(resourceURI)) {
                     exists = true;
                     break;
@@ -275,4 +287,20 @@ public class SessionEditorInput extends URIEditorInput {
         return a;
     }
 
+    @Override
+    public int hashCode() {
+        if (getInput() != null) {
+            return getInput().hashCode();
+        }
+        return super.hashCode();
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (o instanceof SessionEditorInput && getInput() != null) {
+            SessionEditorInput otherSessionEditorInput = (SessionEditorInput) o;
+            return getInput().equals(otherSessionEditorInput.getInput());
+        }
+        return super.equals(o);
+    }
 }
diff --git a/plugins/org.eclipse.sirius.ui/src/org/eclipse/sirius/ui/business/api/session/SessionSpecificEditorInput.java b/plugins/org.eclipse.sirius.ui/src/org/eclipse/sirius/ui/business/api/session/SessionSpecificEditorInput.java
index 40ef5c693f..3cd2545dc7 100644
--- a/plugins/org.eclipse.sirius.ui/src/org/eclipse/sirius/ui/business/api/session/SessionSpecificEditorInput.java
+++ b/plugins/org.eclipse.sirius.ui/src/org/eclipse/sirius/ui/business/api/session/SessionSpecificEditorInput.java
@@ -88,11 +88,6 @@ public class SessionSpecificEditorInput extends SessionEditorInput {
         this.myRepresentationDescriptionName = representationDescriptionName;
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.ui.business.api.session.SessionEditorInput#saveState(org.eclipse.ui.IMemento)
-     */
     @Override
     public void saveState(IMemento memento) {
         super.saveState(memento);
@@ -107,23 +102,12 @@ public class SessionSpecificEditorInput extends SessionEditorInput {
         }
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.ui.business.api.session.SessionEditorInput#loadState(org.eclipse.ui.IMemento)
-     */
     @Override
     protected void loadState(IMemento memento) {
         super.loadState(memento);
         restoreValuesFromMemento(memento);
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.ui.business.api.session.SessionEditorInput#getSession(org.eclipse.emf.transaction.TransactionalEditingDomain,
-     *      org.eclipse.ui.IMemento, org.eclipse.emf.common.util.URI)
-     */
     @Override
     protected Session getSession(URI sessionModelURI) {
         final URI uriWithoutFragment = sessionModelURI.trimFragment();
@@ -131,17 +115,21 @@ public class SessionSpecificEditorInput extends SessionEditorInput {
     }
 
     private Session createSessionFromURIAndMemento(final URI uri) {
+        Session session = null;
         SpecificEditorInputTranformer tranformer = new SpecificEditorInputTranformer();
         tranformer.init(mySiriusURI, myRepresentationDescriptionName);
         try {
-            final DRepresentation representation = tranformer.createSessionAndRepresentation(mySemanticModelPath, uri.toString());
-            return SessionManager.INSTANCE.getSession(((DSemanticDecorator) representation).getTarget());
+            session = SessionManager.INSTANCE.getExistingSession(uri);
+            if (session == null) {
+                final DRepresentation representation = tranformer.createSessionAndRepresentation(mySemanticModelPath, uri.toString());
+                session = SessionManager.INSTANCE.getSession(((DSemanticDecorator) representation).getTarget());
+            }
         } catch (final IOException exception) {
             SiriusEditPlugin.getPlugin().getLog().log(new Status(IStatus.ERROR, SiriusEditPlugin.ID, "Failing of EditorInput transformation.", exception));
         } catch (CoreException exception) {
             SiriusEditPlugin.getPlugin().getLog().log(exception.getStatus());
         }
-        return null;
+        return session;
     }
 
     private void restoreValuesFromMemento(final IMemento memento) {
diff --git a/plugins/org.eclipse.sirius.ui/src/org/eclipse/sirius/ui/tools/internal/editor/AbstractDTreeEditor.java b/plugins/org.eclipse.sirius.ui/src/org/eclipse/sirius/ui/tools/internal/editor/AbstractDTreeEditor.java
index 2ae520603d..f3aa7df8ee 100644
--- a/plugins/org.eclipse.sirius.ui/src/org/eclipse/sirius/ui/tools/internal/editor/AbstractDTreeEditor.java
+++ b/plugins/org.eclipse.sirius.ui/src/org/eclipse/sirius/ui/tools/internal/editor/AbstractDTreeEditor.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2008, 2012 THALES GLOBAL SERVICES.
+ * Copyright (c) 2008, 2015 THALES GLOBAL SERVICES.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -49,7 +49,6 @@ import org.eclipse.sirius.tools.api.permission.DRepresentationPermissionStatusQu
 import org.eclipse.sirius.ui.business.api.dialect.DialectEditor;
 import org.eclipse.sirius.ui.business.api.dialect.DialectEditorDialogFactory;
 import org.eclipse.sirius.ui.business.api.session.IEditingSession;
-import org.eclipse.sirius.ui.business.api.session.SessionEditorInput;
 import org.eclipse.sirius.ui.business.api.session.SessionUIManager;
 import org.eclipse.sirius.ui.business.internal.dialect.TreeEditorDialogFactory;
 import org.eclipse.sirius.ui.tools.api.properties.DTablePropertySheetpage;
@@ -234,7 +233,7 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
     }
 
     /**
-     * Lasily gets the image when there is no write permission of the
+     * Lazily gets the image when there is no write permission of the
      * DRepresentation.
      * 
      * @return the image when there is no write permission of the
@@ -254,6 +253,7 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
      */
     public abstract Image getFrozenRepresentationImage();
 
+    @Override
     public TransactionalEditingDomain getEditingDomain() {
         return session.getTransactionalEditingDomain();
     }
@@ -354,29 +354,17 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
         }
     }
 
-    /**
-     * 
-     * {@inheritDoc}
-     */
     @Override
     public boolean isDirty() {
         final boolean dirty = this.session.getStatus() == SessionStatus.DIRTY;
         return dirty;
     }
 
-    /**
-     * 
-     * {@inheritDoc}
-     */
     @Override
     public boolean isSaveAsAllowed() {
         return false;
     }
 
-    /**
-     * 
-     * {@inheritDoc}
-     */
     @Override
     public void setFocus() {
         if (treeViewerManager != null) {
@@ -421,11 +409,7 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
         return editorDesc;
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.ui.business.api.dialect.DialectEditor#needsRefresh(int)
-     */
+    @Override
     public boolean needsRefresh(int propId) {
         boolean result = false;
         if (propId == DialectEditor.PROP_REFRESH) {
@@ -443,11 +427,6 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
      */
     protected abstract void launchRefresh();
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.ui.part.WorkbenchPart#getAdapter(java.lang.Class)
-     */
     @Override
     public Object getAdapter(@SuppressWarnings("rawtypes") final Class type) {
         Object result = super.getAdapter(type);
@@ -471,11 +450,7 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
         }
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.emf.common.ui.viewer.IViewerProvider#getViewer()
-     */
+    @Override
     public Viewer getViewer() {
         Viewer viewer = null;
         if (treeViewerManager != null) {
@@ -497,11 +472,6 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
         return accessor;
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.ui.part.WorkbenchPart#dispose()
-     */
     @Override
     public void dispose() {
 
@@ -521,12 +491,6 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
         if (getTableViewer() != null) {
             getTableViewer().dispose();
         }
-        // Dispose the session editor input to keep the minimum information to
-        // be restore from the INavigationHistory and EditorHistory.
-        if (getEditorInput() instanceof SessionEditorInput) {
-            ((SessionEditorInput) getEditorInput()).dispose();
-        }
-
         // We need to perform the detachEditor after having disposed the viewer
         // and the editor input to avoid a refresh. A refresh can occurs in the
         // case where the detach triggers the reload of the modified resources
@@ -541,11 +505,6 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
 
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.ui.part.EditorPart#setInput(org.eclipse.ui.IEditorInput)
-     */
     @Override
     public void setInput(final IEditorInput input) {
         super.setInput(input);
@@ -599,9 +558,7 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
         return propertiesUpdateEnabled;
     }
 
-    /**
-     * {@inheritDoc}
-     */
+    @Override
     public void notify(final int changeKind) {
         AbstractDTreeEditorSessionListenerDelegate abstractDTreeEditorSessionListenerDelegate = new AbstractDTreeEditorSessionListenerDelegate(this, changeKind);
         if (Display.getCurrent() == null) {
@@ -640,11 +597,6 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
         return SessionUIManager.INSTANCE.getUISession(session);
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.ui.part.EditorPart#isSaveOnCloseNeeded()
-     */
     @Override
     public boolean isSaveOnCloseNeeded() {
         /*
@@ -669,20 +621,12 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
         return autoRefresh;
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.ui.business.api.dialect.DialectEditor#setDialogFactory(org.eclipse.sirius.ui.business.api.dialect.DialectEditorDialogFactory)
-     */
+    @Override
     public void setDialogFactory(DialectEditorDialogFactory dialogFactory) {
         myDialogFactory = dialogFactory;
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.ui.ISaveablesSource#getSaveables()
-     */
+    @Override
     public Saveable[] getSaveables() {
         if (session != null && session.isOpen()) {
             IEditingSession uiSession = getUISession();
@@ -693,20 +637,12 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
         return new Saveable[0];
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.ui.ISaveablesSource#getActiveSaveables()
-     */
+    @Override
     public Saveable[] getActiveSaveables() {
         return getSaveables();
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see ISaveablePart2#promptToSaveOnClose()
-     */
+    @Override
     public int promptToSaveOnClose() {
         choice = ISaveablePart2.DEFAULT;
         if (session != null && session.isOpen()) {
@@ -720,11 +656,6 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
         return choice;
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.ui.part.WorkbenchPart#createPartControl(org.eclipse.swt.widgets.Composite)
-     */
     @Override
     public void createPartControl(Composite parent) {
         // setting up a UndoActionHandler
@@ -733,31 +664,19 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
         setUpUndoRedoActionHandler();
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.ui.IPageListener#pageOpened(org.eclipse.ui.IWorkbenchPage)
-     */
+    @Override
     public void pageOpened(IWorkbenchPage page) {
 
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.ui.IPageListener#pageActivated(org.eclipse.ui.IWorkbenchPage)
-     */
+    @Override
     public void pageActivated(IWorkbenchPage page) {
         // As the page has been activated, we now can create the
         // UndoRedoActionHandler
         setUpUndoRedoActionHandler();
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.ui.IPageListener#pageClosed(org.eclipse.ui.IWorkbenchPage)
-     */
+    @Override
     public void pageClosed(IWorkbenchPage page) {
 
     }
@@ -808,6 +727,7 @@ public abstract class AbstractDTreeEditor extends EditorPart implements DialectE
         return searchedTreeItem;
     }
 
+    @Override
     public DialectEditorDialogFactory getDialogFactory() {
         return myDialogFactory;
     }