001package org.eclipse.aether.graph;
002
003/*
004 * Licensed to the Apache Software Foundation (ASF) under one
005 * or more contributor license agreements.  See the NOTICE file
006 * distributed with this work for additional information
007 * regarding copyright ownership.  The ASF licenses this file
008 * to you under the Apache License, Version 2.0 (the
009 * "License"); you may not use this file except in compliance
010 * with the License.  You may obtain a copy of the License at
011 * 
012 *  http://www.apache.org/licenses/LICENSE-2.0
013 * 
014 * Unless required by applicable law or agreed to in writing,
015 * software distributed under the License is distributed on an
016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017 * KIND, either express or implied.  See the License for the
018 * specific language governing permissions and limitations
019 * under the License.
020 */
021
022import java.util.List;
023
024/**
025 * 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
026 * same versionless coordinates. In more practical terms, a cycle occurs when a project directly or indirectly depends
027 * on its own output artifact.
028 * 
029 * @noimplement This interface is not intended to be implemented by clients.
030 * @noextend This interface is not intended to be extended by clients.
031 */
032public interface DependencyCycle
033{
034
035    /**
036     * Gets the dependencies that lead to the first dependency on the cycle, starting from the root of the dependency
037     * graph.
038     * 
039     * @return The (read-only) sequence of dependencies that precedes the cycle in the graph, potentially empty but
040     *         never {@code null}.
041     */
042    List<Dependency> getPrecedingDependencies();
043
044    /**
045     * Gets the dependencies that actually form the cycle. For example, a -&gt; b -&gt; c -&gt; a, i.e. the last
046     * dependency in this sequence duplicates the first element and closes the cycle. Hence the length of the cycle is
047     * the size of the returned sequence minus 1.
048     * 
049     * @return The (read-only) sequence of dependencies that forms the cycle, never {@code null}.
050     */
051    List<Dependency> getCyclicDependencies();
052
053}