| // 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.common.base.Verify; |
| import com.google.common.collect.Iterables; |
| import com.google.devtools.build.lib.analysis.config.BuildOptions; |
| import com.google.devtools.build.lib.concurrent.ThreadSafety; |
| import java.util.Collection; |
| import java.util.Map; |
| |
| /** |
| * A configuration transition that maps a single input {@link BuildOptions} to possibly multiple |
| * output {@link BuildOptions}. This provides the ability to transition to multiple configurations |
| * simultaneously. |
| * |
| * <p>Also see {@link PatchTransition}, which maps a single input {@BuildOptions} to a single |
| * output. If your transition never needs to produce multiple outputs, you should use a |
| * {@link PatchTransition}. |
| * |
| * Corresponding rule implementations may require special support to handle this in an organized |
| * way (e.g. for determining which CPU corresponds to which dep for a multi-arch split dependency). |
| */ |
| @ThreadSafety.Immutable |
| @FunctionalInterface |
| public interface SplitTransition extends ConfigurationTransition { |
| /** |
| * Returns the map of {@code BuildOptions} after splitting, or the original options if this split |
| * is a noop. The key values are used as dict keys in ctx.split_attr, so human-readable strings |
| * are recommended. |
| * |
| * <p>Returning an empty or null list triggers a {@link RuntimeException}. |
| */ |
| Map<String, BuildOptions> split(BuildOptions buildOptions); |
| |
| /** |
| * Returns true iff {@code option} and {@splitOptions} are equal. |
| * |
| * <p>This can be used to determine if a split is a noop. |
| */ |
| static boolean equals(BuildOptions options, Collection<BuildOptions> splitOptions) { |
| return splitOptions.size() == 1 && Iterables.getOnlyElement(splitOptions).equals(options); |
| } |
| |
| @Override |
| default Map<String, BuildOptions> apply(BuildOptions buildOptions) { |
| Map<String, BuildOptions> splitOptions = split(buildOptions); |
| Verify.verifyNotNull(splitOptions, "Split transition output may not be null"); |
| Verify.verify(!splitOptions.isEmpty(), "Split transition output may not be empty"); |
| return splitOptions; |
| } |
| |
| @Override |
| default String reasonForOverride() { |
| return "This is a fundamental transition modeling the need for multiply configured deps"; |
| } |
| } |