| // Copyright 2017 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.config.transitions; |
| |
| import com.google.devtools.build.lib.analysis.config.BuildOptions; |
| import java.util.List; |
| |
| /** |
| * A configuration transition. |
| */ |
| public interface ConfigurationTransition { |
| /** |
| * Returns the list of {@code BuildOptions} after applying this transition. |
| * |
| * <p>Returning an empty or null list triggers a {@link RuntimeException}. |
| */ |
| List<BuildOptions> apply(BuildOptions buildOptions); |
| |
| /** |
| * We want to keep the number of transition interfaces no larger than what's necessary to maintain |
| * a clear configuration API. |
| * |
| * <p>This method provides a speed bump against creating new interfaces too casually. While we |
| * could provide stronger enforcement by making {@link ConfigurationTransition} an abstract class |
| * with a limited access constructor, keeping it as an interface supports defining transitions |
| * with lambdas. |
| * |
| * <p>If you're considering adding a new override, contact bazel-dev@googlegroups.com to discuss. |
| */ |
| @SuppressWarnings("unused") |
| String reasonForOverride(); |
| |
| /** |
| * Does this transition switch to a "host" configuration? |
| */ |
| default boolean isHostTransition() { |
| return false; |
| } |
| |
| default String getName() { |
| return this.getClass().getSimpleName(); |
| } |
| |
| /** Allows the given {@link Visitor} to inspect this transition. */ |
| default <E extends Exception> void visit(Visitor<E> visitor) throws E { |
| visitor.accept(this); |
| } |
| |
| /** Helper object that can be used to inspect {@link ConfigurationTransition} instances. */ |
| @FunctionalInterface |
| interface Visitor<E extends Exception> { |
| void accept(ConfigurationTransition transition) throws E; |
| } |
| } |