* specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.project;

import java.util.List;

public class CycleDetectedException extends Exception {
    private final List<String> cycle;

    public CycleDetectedException(String message, List<String> cycle) {
        super(message);
        this.cycle = cycle;
    }

    public List<String> getCycle() {
        return cycle;

package org.apache.maven.graph;

import java.util.Arrays;
import java.util.List;

import org.apache.maven.execution.ProjectDependencyGraph;
import org.apache.maven.model.Dependency;
import org.apache.maven.project.CycleDetectedException;
import org.apache.maven.project.DuplicateProjectException;
import org.apache.maven.project.MavenProject;
import org.junit.jupiter.api.Test;

import static org.junit.jupiter.api.Assertions.assertEquals;

        addEdge(graph1, "a", "b");
        addEdge(graph1, "b", "c");

        Graph graph2 = new Graph();
        addEdge(graph2, "a", "b");
        addEdge(graph2, "b", "c");
        CycleDetectedException cde = assertThrows(CycleDetectedException.class, () -> addEdge(graph2, "c", "a"));
        List<String> cycle = cde.getCycle();
        assertNotNull(cycle, "Cycle should be not null");

    synchronized void addEdge(String from, String to) throws CycleDetectedException {
        if (graph.computeIfAbsent(from, l -> new HashSet<>()).add(to)) {
            List<String> cycle = visitCycle(graph, Collections.singleton(to), new HashMap<>(), new LinkedList<>());
            if (cycle != null) {
                // remove edge which introduced cycle
                throw new CycleDetectedException(

 * under the License.
 */
package org.apache.maven;

import org.apache.maven.project.CycleDetectedException;

/**
 */
public class ProjectCycleException extends BuildFailureException {
    public ProjectCycleException(String message) {
        super(message);
    }

    public ProjectCycleException(String message, CycleDetectedException cause) {
        super(message, cause);
    }

     *
     * @param projects The projects to create the dependency graph with
     * @throws DuplicateProjectException
     * @throws CycleDetectedException
     */
    public DefaultProjectDependencyGraph(Collection<MavenProject> projects)
            throws CycleDetectedException, DuplicateProjectException {
        this(projects, projects);
    }

    /**

    }

    void addEdge(Vertex from, Vertex to) throws CycleDetectedException {
        from.children.add(to);
        to.parents.add(from);
        List<String> cycle = findCycle(to);
        if (cycle != null) {
            // remove edge which introduced cycle
            removeEdge(from, to);
            throw new CycleDetectedException(

    // that seems to work fine. We need to take versions and lifecycle into account.
    public ProjectSorter(Collection<MavenProject> projects) throws CycleDetectedException, DuplicateProjectException {
        graph = new Graph();

        // groupId:artifactId:version -> project
        projectMap = new HashMap<>(projects.size() * 2);

import org.apache.maven.model.Plugin;
import org.apache.maven.model.building.DefaultModelProblem;
import org.apache.maven.model.building.Result;
import org.apache.maven.project.CycleDetectedException;
import org.apache.maven.project.DuplicateProjectException;
import org.apache.maven.project.MavenProject;
import org.apache.maven.project.ProjectBuildingException;

import static org.junit.jupiter.api.Assertions.assertThrows;

@Deprecated
public class GraphTest {

    @Test
    void testCycle() throws Graph.CycleDetectedException {
        Graph graph = new Graph();
        graph.addEdge("a1", "a2");
        assertThrows(Graph.CycleDetectedException.class, () -> graph.addEdge("a2", "a1"));
    }

    @Test
    public void testPerf() throws IOException {