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.collection;
020
021import org.eclipse.aether.graph.Dependency;
022
023/**
024 * Decides what dependencies to include in the dependency graph.
025 * <p>
026 * <strong>Note:</strong> Implementations must be stateless.
027 * <p>
028 * <em>Warning:</em> This hook is called from a hot spot and therefore implementations should pay attention to
029 * performance. Among others, implementations should provide a semantic {@link Object#equals(Object) equals()} method.
030 *
031 * @see org.eclipse.aether.RepositorySystemSession#getDependencySelector()
032 * @see org.eclipse.aether.RepositorySystem#collectDependencies(org.eclipse.aether.RepositorySystemSession,
033 *      CollectRequest)
034 */
035public interface DependencySelector {
036
037    /**
038     * Decides whether the specified dependency should be included in the dependency graph.
039     *
040     * @param dependency The dependency to check, must not be {@code null}.
041     * @return {@code false} if the dependency should be excluded from the children of the current node, {@code true}
042     *         otherwise.
043     */
044    boolean selectDependency(Dependency dependency);
045
046    /**
047     * Derives a dependency selector for the specified collection context. When calculating the child selector,
048     * implementors are strongly advised to simply return the current instance if nothing changed to help save memory.
049     *
050     * @param context The dependency collection context, must not be {@code null}.
051     * @return The dependency selector for the target node or {@code null} if dependencies should be unconditionally
052     *         included in the sub graph.
053     */
054    DependencySelector deriveChildSelector(DependencyCollectionContext context);
055}