001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.eclipse.aether.graph;
020
021import java.util.List;
022
023/**
024 * A cycle within a dependency graph, that is a sequence of dependencies d_1, d_2, ..., d_n where d_1 and d_n have the
025 * same versionless coordinates. In more practical terms, a cycle occurs when a project directly or indirectly depends
026 * on its own output artifact.
027 *
028 * @noimplement This interface is not intended to be implemented by clients.
029 * @noextend This interface is not intended to be extended by clients.
030 */
031public interface DependencyCycle {
032
033    /**
034     * Gets the dependencies that lead to the first dependency on the cycle, starting from the root of the dependency
035     * graph.
036     *
037     * @return The (read-only) sequence of dependencies that precedes the cycle in the graph, potentially empty but
038     *         never {@code null}.
039     */
040    List<Dependency> getPrecedingDependencies();
041
042    /**
043     * Gets the dependencies that actually form the cycle. For example, a -&gt; b -&gt; c -&gt; a, i.e. the last
044     * dependency in this sequence duplicates the first element and closes the cycle. Hence the length of the cycle is
045     * the size of the returned sequence minus 1.
046     *
047     * @return The (read-only) sequence of dependencies that forms the cycle, never {@code null}.
048     */
049    List<Dependency> getCyclicDependencies();
050}