| // 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.Preconditions; |
| import com.google.common.collect.ImmutableList; |
| import com.google.devtools.build.lib.analysis.config.BuildOptions; |
| import java.util.List; |
| |
| /** |
| * A configuration transition that composes two other transitions in an ordered sequence. |
| * |
| * <p>Example: |
| * <pre> |
| * transition1: { someSetting = $oldVal + " foo" } |
| * transition2: { someSetting = $oldVal + " bar" } |
| * ComposingSplitTransition(transition1, transition2): { someSetting = $oldVal + " foo bar" } |
| * </pre> |
| * |
| * <p>Child transitions can be {@link SplitTransition}s, {@link PatchTransition}s, or any |
| * combination thereof. We implement this class as a {@link SplitTransition} since that abstraction |
| * captures all possible combinations. |
| */ |
| public class ComposingSplitTransition implements SplitTransition { |
| private ConfigurationTransition transition1; |
| private ConfigurationTransition transition2; |
| |
| /** |
| * Creates a {@link ComposingSplitTransition} that applies the sequence: |
| * {@code fromOptions -> transition1 -> transition2 -> toOptions }. |
| */ |
| public ComposingSplitTransition(ConfigurationTransition transition1, |
| ConfigurationTransition transition2) { |
| this.transition1 = verifySupported(transition1); |
| this.transition2 = verifySupported(transition2); |
| } |
| |
| @Override |
| public List<BuildOptions> split(BuildOptions buildOptions) { |
| ImmutableList.Builder<BuildOptions> toOptions = ImmutableList.builder(); |
| for (BuildOptions transition1Options : apply(buildOptions, transition1)) { |
| toOptions.addAll(apply(transition1Options, transition2)); |
| } |
| return toOptions.build(); |
| } |
| |
| /** |
| * Verifies support for the given transition type. Throws an {@link IllegalArgumentException} if |
| * unsupported. |
| */ |
| private ConfigurationTransition verifySupported(ConfigurationTransition transition) { |
| Preconditions.checkArgument(transition instanceof PatchTransition |
| || transition instanceof SplitTransition); |
| return transition; |
| } |
| |
| /** |
| * Applies the given transition over the given {@link BuildOptions}, returns the result. |
| */ |
| // TODO(gregce): move this somewhere more general. This isn't intrinsic to composed splits. |
| static List<BuildOptions> apply(BuildOptions fromOptions, ConfigurationTransition transition) { |
| if (transition instanceof PatchTransition) { |
| return ImmutableList.<BuildOptions>of(((PatchTransition) transition).apply(fromOptions)); |
| } else if (transition instanceof SplitTransition) { |
| SplitTransition split = (SplitTransition) transition; |
| List<BuildOptions> splitOptions = split.split(fromOptions); |
| if (splitOptions.isEmpty()) { |
| return ImmutableList.<BuildOptions>of(fromOptions); |
| } else { |
| return splitOptions; |
| } |
| } else { |
| throw new IllegalStateException( |
| String.format("Unsupported composite transition type: %s", |
| transition.getClass().getName())); |
| } |
| } |
| } |