| // Copyright 2014 The Bazel Authors. All rights reserved. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package com.google.devtools.build.lib.analysis; |
| |
| /** |
| * Contains rolled-up data about the transitive closure of a configured target. |
| * |
| * For more information about how analysis works, see |
| * {@link com.google.devtools.build.lib.analysis.RuleConfiguredTargetFactory}. |
| * TransitiveInfoProviders need to be serializable, and for that reason they must conform to |
| * the following restrictions: |
| * |
| * <ul> |
| * <li>The provider interface must directly extend {@code TransitiveInfoProvider}. |
| * <li>Every method must return immutable data.</li> |
| * <li>Every method must return the same object if called multiple times with the same |
| * arguments.</li> |
| * <li>Overloading a method name multiple times is forbidden.</li> |
| * <li>The return type of a method must satisfy one of the following conditions: |
| * <ul> |
| * <li>It must be from the set of {String, Integer, int, Boolean, bool, Label, PathFragment, |
| * Artifact}, OR</li> |
| * <li>it must be an ImmutableList/List/Collection/Iterable of T, where T is either |
| * one of the types above with a default serializer or T implements ValueSerializer, OR</li> |
| * <li>it must be serializable (TBD)</li> |
| * </ul> |
| * <li>If the method takes arguments, it must declare a custom serializer (TBD).</li> |
| * </ul> |
| * |
| * <p>Some typical uses of this interface are: |
| * <ul> |
| * <li>The set of Python source files in the transitive closure of this rule |
| * <li>The set of declared C++ header files in the transitive closure |
| * <li>The files that need to be built when the target is mentioned on the command line |
| * </ul> |
| * |
| * <p>Note that if implemented naively, this would result in the memory requirements |
| * being O(n^2): in a long dependency chain, if every target adds one single artifact, storing the |
| * transitive closures of every rule would take 1+2+3+...+n-1+n = O(n^2) memory. |
| * |
| * <p>In order to avoid this, we introduce the concept of nested sets, {@link |
| * com.google.devtools.build.lib.collect.nestedset.NestedSet}. A nested set is an immutable |
| * data structure that can contain direct members and other nested sets (recursively). Nested sets |
| * are iterable and can be flattened into ordered sets, where the order depends on which |
| * implementation of NestedSet you pick. |
| * |
| * @see TransitiveInfoCollection |
| * @see com.google.devtools.build.lib.analysis.RuleConfiguredTargetFactory |
| */ |
| public interface TransitiveInfoProvider { |
| |
| } |
