Adds onDispose method on the resource set hooks.

The resources are unloaded and removed from the resource set on a
compare input change event using this mechanism.

Change-Id: Ifed4997876456ff0f70f4cb4e072526d5f310347

8 files changed, 316 insertions, 53 deletions

diff --git a/plugins/org.eclipse.emf.compare.diagram.ide.ui.papyrus/src/org/eclipse/emf/compare/diagram/ide/ui/papyrus/internal/CssInstallationHook.java b/plugins/org.eclipse.emf.compare.diagram.ide.ui.papyrus/src/org/eclipse/emf/compare/diagram/ide/ui/papyrus/internal/CssInstallationHook.java
index 7a693092e..5d5b60446 100644
--- a/plugins/org.eclipse.emf.compare.diagram.ide.ui.papyrus/src/org/eclipse/emf/compare/diagram/ide/ui/papyrus/internal/CssInstallationHook.java
+++ b/plugins/org.eclipse.emf.compare.diagram.ide.ui.papyrus/src/org/eclipse/emf/compare/diagram/ide/ui/papyrus/internal/CssInstallationHook.java
@@ -13,22 +13,24 @@ package org.eclipse.emf.compare.diagram.ide.ui.papyrus.internal;
 import java.util.Collection;
 
 import org.eclipse.emf.common.util.URI;
-import org.eclipse.emf.compare.ide.hook.IResourceSetHook;
+import org.eclipse.emf.compare.ide.hook.AbstractResourceSetHooks;
 import org.eclipse.emf.ecore.resource.ResourceSet;
 import org.eclipse.papyrus.infra.gmfdiag.css.helper.CSSHelper;
 
 /**
- * Hook in the EMF Compare {@link ResourceSet} in order to make it able to handle papyrus CSS features.
+ * Hook in the EMF Compare {@link org.eclipse.emf.ecore.resource.ResourceSet} in order to make it able to
+ * handle papyrus CSS features.
  * 
  * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>
  */
-public class CssInstallationHook implements IResourceSetHook {
+public class CssInstallationHook extends AbstractResourceSetHooks {
 
 	/**
 	 * {@inheritDoc}
 	 * 
 	 * @see org.eclipse.emf.compare.ide.internal.utils.IResourceSetHook#handle(java.lang.Iterable)
 	 */
+	@Override
 	public boolean isHookFor(Collection<? extends URI> uris) {
 		// Looks for a papyrus notation file.
 		for (URI uri : uris) {
@@ -46,24 +48,14 @@ public class CssInstallationHook implements IResourceSetHook {
 	/**
 	 * {@inheritDoc}
 	 * 
-	 * @see org.eclipse.emf.compare.ide.hook.IResourceSetHook#preLoadingHook(org.eclipse.emf.ecore.resource.ResourceSet,
+	 * @see org.eclipse.emf.compare.ide.hook.AbstractResourceSetHooks#preLoadingHook(org.eclipse.emf.ecore.resource.ResourceSet,
 	 *      java.util.Collection)
 	 */
+	@Override
 	public void preLoadingHook(ResourceSet resourceSet, Collection<? extends URI> uris) {
 		if (!CSSHelper.isCSSSupported(resourceSet)) {
 			CSSHelper.installCSSSupport(resourceSet);
 		}
-
-	}
-
-	/**
-	 * {@inheritDoc}
-	 * 
-	 * @see org.eclipse.emf.compare.ide.hook.IResourceSetHook#postLoadingHook(org.eclipse.emf.ecore.resource.ResourceSet,
-	 *      java.util.Collection)
-	 */
-	public void postLoadingHook(ResourceSet resourceSet, Collection<? extends URI> uris) {
-		// Nothing to do
 	}
 
 }
diff --git a/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/structuremergeviewer/EMFCompareStructureMergeViewer.java b/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/structuremergeviewer/EMFCompareStructureMergeViewer.java
index dc5bc3529..2164fd630 100644
--- a/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/structuremergeviewer/EMFCompareStructureMergeViewer.java
+++ b/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/structuremergeviewer/EMFCompareStructureMergeViewer.java
@@ -70,6 +70,7 @@ import org.eclipse.emf.compare.Match;
 import org.eclipse.emf.compare.command.ICompareCopyCommand;
 import org.eclipse.emf.compare.domain.ICompareEditingDomain;
 import org.eclipse.emf.compare.domain.impl.EMFCompareEditingDomain;
+import org.eclipse.emf.compare.ide.internal.utils.DisposableResourceSet;
 import org.eclipse.emf.compare.ide.ui.internal.EMFCompareIDEUIMessages;
 import org.eclipse.emf.compare.ide.ui.internal.EMFCompareIDEUIPlugin;
 import org.eclipse.emf.compare.ide.ui.internal.configuration.EMFCompareConfiguration;
@@ -221,7 +222,7 @@ public class EMFCompareStructureMergeViewer extends AbstractStructuredViewerWrap
 	 * When comparing EObjects from a resource, the resource involved doesn't need to be unload by EMF
 	 * Compare.
 	 */
-	private boolean resourcesShouldBeUnload;
+	private boolean resourceSetShouldBeDisposed;
 
 	private DependencyData dependencyData;
 
@@ -867,13 +868,13 @@ public class EMFCompareStructureMergeViewer extends AbstractStructuredViewerWrap
 	void compareInputChanged(final ICompareInput input, IProgressMonitor monitor) {
 		if (input != null) {
 			if (input instanceof CompareInputAdapter) {
-				resourcesShouldBeUnload = false;
+				resourceSetShouldBeDisposed = false;
 				compareInputChanged((CompareInputAdapter)input, monitor);
 			} else if (input instanceof ComparisonScopeInput) {
-				resourcesShouldBeUnload = false;
+				resourceSetShouldBeDisposed = false;
 				compareInputChanged((ComparisonScopeInput)input, monitor);
 			} else {
-				resourcesShouldBeUnload = true;
+				resourceSetShouldBeDisposed = true;
 				SubMonitor subMonitor = SubMonitor.convert(monitor, 100);
 
 				final ITypedElement left = input.getLeft();
@@ -1058,10 +1059,10 @@ public class EMFCompareStructureMergeViewer extends AbstractStructuredViewerWrap
 
 		editingDomainChange(getCompareConfiguration().getEditingDomain(), null);
 
-		if (resourcesShouldBeUnload) {
-			unload(leftResourceSet);
-			unload(rightResourceSet);
-			unload(originResourceSet);
+		if (resourceSetShouldBeDisposed) {
+			disposeResourceSet(leftResourceSet);
+			disposeResourceSet(rightResourceSet);
+			disposeResourceSet(originResourceSet);
 		}
 
 		if (getCompareConfiguration() != null) {
@@ -1071,6 +1072,20 @@ public class EMFCompareStructureMergeViewer extends AbstractStructuredViewerWrap
 	}
 
 	/**
+	 * Disposes the {@link ResourceSet}.
+	 * 
+	 * @param resourceSet
+	 *            that need to be disposed.
+	 */
+	protected void disposeResourceSet(ResourceSet resourceSet) {
+		if (resourceSet instanceof DisposableResourceSet) {
+			((DisposableResourceSet)resourceSet).dispose();
+		} else {
+			unload(resourceSet);
+		}
+	}
+
+	/**
 	 * Handle the erase item event. When select a difference in the structure merge viewer, highlight required
 	 * differences with a specific color, and highlight unmergeable differences with another color.
 	 * 
diff --git a/plugins/org.eclipse.emf.compare.ide/plugin.xml b/plugins/org.eclipse.emf.compare.ide/plugin.xml
index 52622d754..3d034df54 100644
--- a/plugins/org.eclipse.emf.compare.ide/plugin.xml
+++ b/plugins/org.eclipse.emf.compare.ide/plugin.xml
@@ -14,4 +14,10 @@
 
 <plugin>
    <extension-point id="resourceSetHook" name="Resource Set Hook" schema="schema/resourceSetHook.exsd"/>
+   <extension
+         point="org.eclipse.emf.compare.ide.resourceSetHook">
+      <resourceSetHook
+            class="org.eclipse.emf.compare.ide.internal.utils.UnloadingResourceSetHook">
+      </resourceSetHook>
+   </extension>
 </plugin>
diff --git a/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/hook/AbstractResourceSetHooks.java b/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/hook/AbstractResourceSetHooks.java
new file mode 100644
index 000000000..8d505e247
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/hook/AbstractResourceSetHooks.java
@@ -0,0 +1,60 @@
+/*******************************************************************************
+ * Copyright (c) 2014 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.emf.compare.ide.hook;
+
+import java.util.Collection;
+
+import org.eclipse.emf.common.util.URI;
+import org.eclipse.emf.ecore.resource.Resource;
+import org.eclipse.emf.ecore.resource.ResourceSet;
+
+/**
+ * Abstract implementation of {@link IResourceSetHook}.
+ * 
+ * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>
+ */
+public abstract class AbstractResourceSetHooks implements IResourceSetHook {
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.ide.hook.IResourceSetHook#isHookFor(java.util.Collection)
+	 */
+	public boolean isHookFor(Collection<? extends URI> uris) {
+		return true;
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.ide.hook.IResourceSetHook#preLoadingHook(org.eclipse.emf.ecore.resource.ResourceSet,
+	 *      java.util.Collection)
+	 */
+	public void preLoadingHook(ResourceSet resourceSet, Collection<? extends URI> uris) {
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.ide.hook.IResourceSetHook#postLoadingHook(org.eclipse.emf.ecore.resource.ResourceSet,
+	 *      java.util.Collection)
+	 */
+	public void postLoadingHook(ResourceSet resourceSet, Collection<? extends URI> uris) {
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.ide.hook.IResourceSetHook#onDispose(java.lang.Iterable)
+	 */
+	public void onDispose(Iterable<Resource> resources) {
+	}
+}
diff --git a/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/hook/IResourceSetHook.java b/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/hook/IResourceSetHook.java
index 6a4d7c930..9774060f9 100644
--- a/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/hook/IResourceSetHook.java
+++ b/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/hook/IResourceSetHook.java
@@ -13,6 +13,7 @@ package org.eclipse.emf.compare.ide.hook;
 import java.util.Collection;
 
 import org.eclipse.emf.common.util.URI;
+import org.eclipse.emf.ecore.resource.Resource;
 import org.eclipse.emf.ecore.resource.ResourceSet;
 
 /**
@@ -56,4 +57,18 @@ public interface IResourceSetHook {
 	 */
 	void postLoadingHook(ResourceSet resourceSet, Collection<? extends URI> uris);
 
+	/**
+	 * This will be called when the resource set is disposed (if it is).
+	 * <p>
+	 * By default, EMF Compare will not unload any resource. Still some resources might need to be unloaded.
+	 * This method could be a good way to do it. Hooks are called in unspecified order, so resources may
+	 * already have been unloaded by other hooks when yours is called.
+	 * </p>
+	 * 
+	 * @see org.eclipse.emf.compare.ide.internal.utils.DisposableResourceSet
+	 * @param resources
+	 *            List of {@link Resource}s currently in the resource set.
+	 */
+	void onDispose(Iterable<Resource> resources);
+
 }
diff --git a/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/internal/utils/DisposableResourceSet.java b/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/internal/utils/DisposableResourceSet.java
new file mode 100644
index 000000000..8122e465b
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/internal/utils/DisposableResourceSet.java
@@ -0,0 +1,27 @@
+/*******************************************************************************
+ * Copyright (c) 2014 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.emf.compare.ide.internal.utils;
+
+import org.eclipse.emf.ecore.resource.ResourceSet;
+
+/**
+ * A {@link ResourceSet} that offers a dispose method.
+ * 
+ * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>
+ */
+public interface DisposableResourceSet extends ResourceSet {
+
+	/**
+	 * This method should be called when the resource set is no longer needed.
+	 */
+	void dispose();
+
+}
diff --git a/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/internal/utils/NotLoadingResourceSet.java b/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/internal/utils/NotLoadingResourceSet.java
index 36907e987..60058db5e 100644
--- a/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/internal/utils/NotLoadingResourceSet.java
+++ b/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/internal/utils/NotLoadingResourceSet.java
@@ -37,7 +37,9 @@ import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.OperationCanceledException;
 import org.eclipse.core.runtime.Status;
 import org.eclipse.core.runtime.SubMonitor;
+import org.eclipse.emf.common.notify.Notifier;
 import org.eclipse.emf.common.util.EList;
+import org.eclipse.emf.common.util.TreeIterator;
 import org.eclipse.emf.common.util.URI;
 import org.eclipse.emf.common.util.WrappedException;
 import org.eclipse.emf.compare.ide.EMFCompareIDEPlugin;
@@ -67,7 +69,7 @@ import org.eclipse.emf.ecore.util.InternalEList;
  * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
  */
 @Beta
-public final class NotLoadingResourceSet extends ResourceSetImpl {
+public final class NotLoadingResourceSet extends ResourceSetImpl implements DisposableResourceSet {
 
 	/**
 	 * Function to transform a {@link IStorage} in an {@link URI}.
@@ -85,13 +87,26 @@ public final class NotLoadingResourceSet extends ResourceSetImpl {
 	private final StorageTraversal storageTranversal;
 
 	/**
+	 * Registry holding {@link IResourceSetHook}s.
+	 */
+	private final ResourceSetHookRegistry hookRegistry;
+
+	/**
+	 * Holds <code>true</code> if the resource set has been disposed.
+	 */
+	private boolean isDisposed;
+
+	/**
 	 * Constructor.
 	 * 
 	 * @param storageTranversal
 	 *            see {@link #storageTranversal}.
+	 * @param hookRegistry
+	 *            Registry holding {@link IResourceSetHook}s.
 	 */
-	private NotLoadingResourceSet(StorageTraversal storageTranversal) {
+	private NotLoadingResourceSet(StorageTraversal storageTranversal, ResourceSetHookRegistry hookRegistry) {
 		this.storageTranversal = storageTranversal;
+		this.hookRegistry = hookRegistry;
 	}
 
 	/**
@@ -110,41 +125,24 @@ public final class NotLoadingResourceSet extends ResourceSetImpl {
 			ResourceSetHookRegistry resourceSetHookRegistry) {
 		SubMonitor progress = SubMonitor.convert(monitor, 100);
 		progress.subTask(EMFCompareIDEMessages.getString("NotLoadingResourceSet.monitor.resolve")); //$NON-NLS-1$
-		final NotLoadingResourceSet resourceSet = new NotLoadingResourceSet(traversals);
+		final NotLoadingResourceSet resourceSet = new NotLoadingResourceSet(traversals,
+				resourceSetHookRegistry);
 
 		final Set<? extends IStorage> storages = traversals.getStorages();
 
 		resourceSet.setURIResourceMap(new HashMap<URI, Resource>(storages.size() << 1));
 
-		final Collection<URI> urisToLoad = ImmutableList.copyOf(transform(storages, TO_URI));
-
-		final Collection<IResourceSetHook> hooks = getMatchingHooks(resourceSetHookRegistry, urisToLoad);
-
-		for (IResourceSetHook hook : hooks) {
-			hook.preLoadingHook(resourceSet, urisToLoad);
-		}
-
 		// loading is 60% of the total work?
 		final int loadWorkPercentage = 60;
 		SubMonitor subMonitor = progress.newChild(loadWorkPercentage).setWorkRemaining(
 				traversals.getStorages().size());
 
-		for (URI uri : urisToLoad) {
-			if (monitor.isCanceled()) {
-				throw new OperationCanceledException();
-			}
-			// Forces the loading of the selected resources.
-			resourceSet.loadResource(uri);
-			subMonitor.worked(1);
-		}
-
-		for (IResourceSetHook hook : hooks) {
-			hook.postLoadingHook(resourceSet, urisToLoad);
-		}
+		resourceSet.load(subMonitor);
 
 		final int resolveWorkPercentage = 40;
 		subMonitor = progress.newChild(resolveWorkPercentage).setWorkRemaining(
 				resourceSet.getResources().size());
+
 		// Then resolve all proxies between our "loaded" resources.
 		List<Resource> resourcesCopy = newArrayList(resourceSet.getResources());
 		for (Resource res : resourcesCopy) {
@@ -162,19 +160,16 @@ public final class NotLoadingResourceSet extends ResourceSetImpl {
 	/**
 	 * Retrieves the hooks that need to be hooked on this resource set.
 	 * 
-	 * @param resourceSetHookRegistry
-	 *            Registry holding the hooks.
 	 * @param urisToLoad
 	 *            The collection of uris that will be loaded.
 	 * @return {@link Collection} of {@link IResourceSetHook}s that need to be hocked.
 	 */
-	private static Collection<IResourceSetHook> getMatchingHooks(
-			ResourceSetHookRegistry resourceSetHookRegistry, final Collection<URI> urisToLoad) {
+	private Collection<IResourceSetHook> getMatchingHooks(final Collection<URI> urisToLoad) {
 		final Collection<IResourceSetHook> hooks;
-		if (resourceSetHookRegistry == null) {
+		if (hookRegistry == null) {
 			hooks = Collections.emptyList();
 		} else {
-			hooks = Collections2.filter(resourceSetHookRegistry.getResourceSetHooks(),
+			hooks = Collections2.filter(hookRegistry.getResourceSetHooks(),
 					new Predicate<IResourceSetHook>() {
 
 						public boolean apply(IResourceSetHook input) {
@@ -186,7 +181,7 @@ public final class NotLoadingResourceSet extends ResourceSetImpl {
 	}
 
 	/**
-	 * Adds ResourceSetHook extension point. {@inheritDoc}
+	 * {@inheritDoc}
 	 * 
 	 * @see org.eclipse.emf.ecore.resource.impl.ResourceSetImpl#demandLoadHelper(org.eclipse.emf.ecore.resource.Resource)
 	 */
@@ -308,6 +303,8 @@ public final class NotLoadingResourceSet extends ResourceSetImpl {
 	 */
 	@Override
 	public Resource getResource(URI uri, boolean loadOnDemand) {
+		checkNotDisposed();
+
 		ILoadOnDemandPolicy.Registry registry = EMFCompareRCPPlugin.getDefault()
 				.getLoadOnDemandPolicyRegistry();
 		if (registry.hasAnyAuthorizingPolicy(uri)) {
@@ -381,4 +378,118 @@ public final class NotLoadingResourceSet extends ResourceSetImpl {
 			}
 		}
 	}
+
+	/**
+	 * Loads resources from the {@link StorageTraversal}.
+	 * 
+	 * @see #storageTranversal
+	 * @param monitor
+	 *            {@link IProgressMonitor} reporting progress.
+	 */
+	private void load(IProgressMonitor monitor) {
+		checkNotDisposed();
+
+		final Collection<URI> urisToLoad = ImmutableList.copyOf(transform(storageTranversal.getStorages(),
+				TO_URI));
+
+		final Collection<IResourceSetHook> hooks = getMatchingHooks(urisToLoad);
+
+		for (IResourceSetHook hook : hooks) {
+			hook.preLoadingHook(this, urisToLoad);
+		}
+
+		for (URI uri : urisToLoad) {
+			if (monitor.isCanceled()) {
+				throw new OperationCanceledException();
+			}
+			// Forces the loading of the selected resources.
+			loadResource(uri);
+			monitor.worked(1);
+		}
+
+		for (IResourceSetHook hook : hooks) {
+			hook.postLoadingHook(this, urisToLoad);
+		}
+
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.ide.internal.utils.DisposableResourceSet#dispose()
+	 */
+	public void dispose() {
+		ImmutableList<Resource> currentResources = ImmutableList.copyOf(getResources());
+		isDisposed = true;
+		Collection<URI> resourceSetUris = newArrayList(transform(currentResources,
+				new Function<Resource, URI>() {
+
+					public URI apply(Resource input) {
+						return input.getURI();
+					}
+				}));
+		for (IResourceSetHook hook : getMatchingHooks(resourceSetUris)) {
+			hook.onDispose(currentResources);
+		}
+		getResources().clear();
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.ecore.resource.impl.ResourceSetImpl#createResource(org.eclipse.emf.common.util.URI,
+	 *      java.lang.String)
+	 */
+	@Override
+	public Resource createResource(URI uri, String contentType) {
+		checkNotDisposed();
+		return super.createResource(uri, contentType);
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.ecore.resource.impl.ResourceSetImpl#getEObject(org.eclipse.emf.common.util.URI,
+	 *      boolean)
+	 */
+	@Override
+	public EObject getEObject(URI uri, boolean loadOnDemand) {
+		checkNotDisposed();
+		return super.getEObject(uri, loadOnDemand);
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.ecore.resource.impl.ResourceSetImpl#getAllContents()
+	 */
+	@Override
+	public TreeIterator<Notifier> getAllContents() {
+		checkNotDisposed();
+		return super.getAllContents();
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.ecore.resource.impl.ResourceSetImpl#getResources()
+	 */
+	@Override
+	public EList<Resource> getResources() {
+		checkNotDisposed();
+		return super.getResources();
+	}
+
+	/**
+	 * Checks that the resource set is not disposed. If it is throws an {@link IllegalStateException}.
+	 * 
+	 * @throws IllegalStateException
+	 *             If the resource set is disposed.
+	 */
+	private void checkNotDisposed() {
+		if (isDisposed) {
+			throw new IllegalStateException("The resource set is disposed"); //$NON-NLS-1$
+		}
+	}
+
 }
diff --git a/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/internal/utils/UnloadingResourceSetHook.java b/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/internal/utils/UnloadingResourceSetHook.java
new file mode 100644
index 000000000..fe95f17de
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.ide/src/org/eclipse/emf/compare/ide/internal/utils/UnloadingResourceSetHook.java
@@ -0,0 +1,37 @@
+/*******************************************************************************
+ * Copyright (c) 2014 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.emf.compare.ide.internal.utils;
+
+import org.eclipse.emf.compare.ide.hook.AbstractResourceSetHooks;
+import org.eclipse.emf.ecore.resource.Resource;
+
+/**
+ * Hook that unloads resources from the resource set on dipose.
+ * 
+ * @author <a href="mailto:arthur.daussy@obeo.fr">Arthur Daussy</a>
+ */
+public class UnloadingResourceSetHook extends AbstractResourceSetHooks {
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.ide.hook.AbstractResourceSetHooks#onDispose(java.lang.Iterable)
+	 */
+	@Override
+	public void onDispose(Iterable<Resource> resources) {
+		for (Resource resource : resources) {
+			if (resource.isLoaded()) {
+				resource.unload();
+			}
+		}
+	}
+
+}