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// 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.List;
/**
* 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 list of {@code BuildOptions} after splitting, or the original options if this
* split is a noop.
*
* <p>Returning an empty or null list triggers a {@link RuntimeException}.
*/
List<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, List<BuildOptions> splitOptions) {
return splitOptions.size() == 1 && Iterables.getOnlyElement(splitOptions).equals(options);
}
@Override
default List<BuildOptions> apply(BuildOptions buildOptions) {
List<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";
}
}
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