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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *   http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing,
13   * software distributed under the License is distributed on an
14   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   * KIND, either express or implied.  See the License for the
16   * specific language governing permissions and limitations
17   * under the License.
18   */
19  package org.eclipse.aether.collection;
20  
21  import org.eclipse.aether.graph.Dependency;
22  
23  /**
24   * Decides what dependencies to include in the dependency graph.
25   * <p>
26   * <strong>Note:</strong> Implementations must be stateless.
27   * <p>
28   * <em>Warning:</em> This hook is called from a hot spot and therefore implementations should pay attention to
29   * performance. Among others, implementations should provide a semantic {@link Object#equals(Object) equals()} method.
30   *
31   * @see org.eclipse.aether.RepositorySystemSession#getDependencySelector()
32   * @see org.eclipse.aether.RepositorySystem#collectDependencies(org.eclipse.aether.RepositorySystemSession,
33   *      CollectRequest)
34   */
35  public interface DependencySelector {
36  
37      /**
38       * Decides whether the specified dependency should be included in the dependency graph.
39       *
40       * @param dependency The dependency to check, must not be {@code null}.
41       * @return {@code false} if the dependency should be excluded from the children of the current node, {@code true}
42       *         otherwise.
43       */
44      boolean selectDependency(Dependency dependency);
45  
46      /**
47       * Derives a dependency selector for the specified collection context. When calculating the child selector,
48       * implementors are strongly advised to simply return the current instance if nothing changed to help save memory.
49       *
50       * @param context The dependency collection context, must not be {@code null}.
51       * @return The dependency selector for the target node or {@code null} if dependencies should be unconditionally
52       *         included in the sub graph.
53       */
54      DependencySelector deriveChildSelector(DependencyCollectionContext context);
55  }