// 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;
import com.google.devtools.build.lib.packages.Attribute;
/**
* Interface for a configuration transition using dynamic configurations.
*
* <p>The concept is simple: given the input configuration's build options, the
* transition does whatever it wants to them and returns the modified result.
*
* <p>Implementations must be stateless: the transformation logic cannot use
* any information from any data besides the input build options.
*
* <p>For performance reasons, the input options are passed in as a <i>reference</i>,
* not a <i>copy</i>. Transition implementations should <i>always</i> treat these
* options as immutable, and call
* {@link com.google.devtools.build.lib.analysis.config.BuildOptions#clone}
* before applying any mutations. Unfortunately,
* {@link com.google.devtools.build.lib.analysis.config.BuildOptions} does not currently
* enforce immutability, so care must be taken not to modify the wrong instance.
*/
public interface PatchTransition extends Attribute.Transition {
/**
* 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 apply(BuildOptions options);
}