OO-2467: prevent infinite loop with the previous button in assessment tool

src/main/java/org/olat/course/assessment/ui/tool/AssessmentIdentityCourseController.java

@@ -43,6 +43,7 @@ import org.olat.course.CourseFactory;
 import org.olat.course.ICourse;
 import org.olat.course.assessment.ui.tool.event.CourseNodeEvent;
 import org.olat.course.config.CourseConfig;
+import org.olat.course.nodes.AssessableCourseNode;
 import org.olat.course.nodes.CourseNode;
 import org.olat.course.nodes.CourseNodeFactory;
 import org.olat.course.nodes.STCourseNode;
@@ -229,8 +230,10 @@ public class AssessmentIdentityCourseController extends BasicController implemen
 		CourseNode previousNode = treeOverviewCtrl.getPreviousNode(currentNodeCtrl.getCourseNode());
 		if(previousNode != null && previousNode.getParent() != null) {
 			if(previousNode instanceof STCourseNode) {
-				for(previousNode=treeOverviewCtrl.getPreviousNode(previousNode); previousNode instanceof STCourseNode; ) {
+				CourseNode node = previousNode;
+				for(previousNode=treeOverviewCtrl.getPreviousNode(previousNode); previousNode instanceof STCourseNode && node != previousNode; ) {
 					//search the previous node which is not a structure node
+					node = previousNode;
 				}
 			}
 
@@ -256,12 +259,9 @@ public class AssessmentIdentityCourseController extends BasicController implemen
 		listenTo(currentNodeCtrl);
 		stackPanel.pushController(courseNode.getShortTitle(), currentNodeCtrl);
 		
-		int index = treeOverviewCtrl.getIndexOf(courseNode);
-		int numOfNodes = treeOverviewCtrl.getNumberOfNodes();
-		
 		previousLink = LinkFactory.createToolLink("previouselement", translate("previous"), this, "o_icon_previous");
 		previousLink.setTitle(translate("command.previous"));
-		previousLink.setEnabled(index > 1 && index <= numOfNodes);
+		previousLink.setEnabled(hasPrevious(courseNode));
 		stackPanel.addTool(previousLink, Align.rightEdge, false);
 
 		courseNodeSelectionLink =  LinkFactory.createToolLink("node.select", "node.select", courseNode.getShortTitle(), this);
@@ -279,4 +279,18 @@ public class AssessmentIdentityCourseController extends BasicController implemen
 		nextLink.setEnabled(hasNext);
 		stackPanel.addTool(nextLink, Align.rightEdge, false);
 	}
-}
+	
+	private boolean hasPrevious(CourseNode courseNode) {
+		int index = treeOverviewCtrl.getIndexOf(courseNode);
+		int numOfNodes = treeOverviewCtrl.getNumberOfNodes();
+		if(index > 0 && index <= numOfNodes) {
+			for(int i=index; i-->0; ) {
+				CourseNode previousNode = treeOverviewCtrl.getNode(i);
+				if(previousNode instanceof AssessableCourseNode && !(previousNode instanceof STCourseNode)) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+}
\ No newline at end of file

src/main/java/org/olat/course/assessment/ui/tool/IdentityAssessmentOverviewController.java

@@ -150,6 +150,11 @@ public class IdentityAssessmentOverviewController extends FormBasicController im
 		return tableModel.getRowCount();
 	}
 	
+	public CourseNode getNode(int row) {
+		AssessmentNodeData data = tableModel.getObject(row);
+		return getNodeByIdent(data.getIdent());
+	}
+	
 	public CourseNode getNodeByIdent(String ident) {
 		return runStructure.getNode(ident);
 	}