// Copyright 2015 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.collect.ImmutableList; import com.google.devtools.build.lib.analysis.config.BuildOptions; import java.util.List; /** * A configuration transition that maps a single input {@link BuildOptions} to a single output * {@link BuildOptions}. * *
Also see {@link SplitTransition}, which maps a single input {@link BuildOptions} to possibly * multiple {@link BuildOptions}. * *
The concept is simple: given the input configuration's build options, the * transition does whatever it wants to them and returns the modified result. * *
Implementations must be stateless: the output must exclusively depend on the * input build options and any immutable member fields. Implementations must also override * {@link Object#equals} and {@link Object#hashCode} unless exclusively accessed as * singletons. For example: * *
* public class MyTransition implements PatchTransition { * public MyTransition INSTANCE = new MyTransition(); * * private MyTransition() {} * * {@literal @}Override * public BuildOptions patch(BuildOptions options) { * BuildOptions toOptions = options.clone(); * // Change some setting on toOptions * return toOptions; * } * } ** *
For performance reasons, the input options are passed as a reference, not a
* copy. Implementations should always treat these as immutable, and call
* {@link com.google.devtools.build.lib.analysis.config.BuildOptions#clone}
* before making changes. Unfortunately,
* {@link com.google.devtools.build.lib.analysis.config.BuildOptions} doesn't currently
* enforce immutability. So care must be taken not to modify the wrong instance.
*/
@FunctionalInterface
public interface PatchTransition extends ConfigurationTransition {
/**
* Applies the transition.
*
* @param options the options representing the input configuration to this transition. DO NOT
* MODIFY THIS VARIABLE WITHOUT CLONING IT FIRST!
* @return the options representing the desired post-transition configuration
*/
BuildOptions patch(BuildOptions options);
@Override
default List