Do not expand same class twice in (quick) type hierarchy

Requires
eclipse-platform/eclipse.platform.ui#2692
Fixes eclipse-jdt#1830

Author: fedejeanne

org.eclipse.jdt.ui/.settings/.api_filters

@@ -137,6 +137,14 @@
             </message_arguments>
         </filter>
     </resource>
+    <resource path="ui/org/eclipse/jdt/internal/ui/typehierarchy/HierarchyInformationControl.java" type="org.eclipse.jdt.internal.ui.typehierarchy.HierarchyInformationControl">
+        <filter id="571519004">
+            <message_arguments>
+                <message_argument value="org.eclipse.jdt.internal.ui.typehierarchy.HierarchyInformationControl.createTreeViewer(Composite, int)"/>
+                <message_argument value="TreeViewer"/>
+            </message_arguments>
+        </filter>
+    </resource>
     <resource path="ui/org/eclipse/jdt/internal/ui/viewsupport/ProblemTableViewer.java" type="org.eclipse.jdt.internal.ui.viewsupport.ProblemTableViewer">
         <filter id="571473929">
             <message_arguments>

org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/typehierarchy/HierarchyInformationControl.java

@@ -14,6 +14,9 @@
 package org.eclipse.jdt.internal.ui.typehierarchy;
 
 import java.lang.reflect.InvocationTargetException;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.function.Predicate;
 
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.events.KeyAdapter;
@@ -23,6 +26,7 @@
 import org.eclipse.swt.widgets.Shell;
 import org.eclipse.swt.widgets.Text;
 import org.eclipse.swt.widgets.Tree;
+import org.eclipse.swt.widgets.Widget;
 
 import org.eclipse.jface.bindings.TriggerSequence;
 import org.eclipse.jface.bindings.keys.KeySequence;
@@ -130,7 +134,23 @@ protected TreeViewer createTreeViewer(Composite parent, int style) {
 		gd.heightHint= tree.getItemHeight() * 12;
 		tree.setLayoutData(gd);
 
-		TreeViewer treeViewer= new TreeViewer(tree);
+		TreeViewer treeViewer= new TreeViewer(tree) {
+			@Override
+			protected Predicate<Widget> getShouldWidgetExpand() {
+
+				Set<Object> expanded= new HashSet<>();
+
+				// Expand every class/interface only once
+				return w -> {
+					if (w == null) {
+						return false;
+					}
+
+					Object data= w.getData();
+					return data == null || expanded.add(data);
+				};
+			}
+		};
 		treeViewer.addFilter(new ViewerFilter() {
 			@Override
 			public boolean select(Viewer viewer, Object parentElement, Object element) {

org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/typehierarchy/TypeHierarchyViewer.java

@@ -13,10 +13,15 @@
  *******************************************************************************/
 package org.eclipse.jdt.internal.ui.typehierarchy;
 
+import java.util.HashSet;
+import java.util.Set;
+import java.util.function.Predicate;
+
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.widgets.Composite;
 import org.eclipse.swt.widgets.Menu;
 import org.eclipse.swt.widgets.Tree;
+import org.eclipse.swt.widgets.Widget;
 
 import org.eclipse.core.runtime.Assert;
 
@@ -182,4 +187,19 @@ protected TypeHierarchyContentProvider getHierarchyContentProvider() {
 		return (TypeHierarchyContentProvider)getContentProvider();
 	}
 
+	@Override
+	protected Predicate<Widget> getShouldWidgetExpand() {
+		Set<Object> expanded= new HashSet<>();
+
+		// Expand every class/interface only once
+		return w -> {
+			if (w == null) {
+				return false;
+			}
+
+			Object data= w.getData();
+			return data == null || expanded.add(data);
+		};
+	}
+
 }