blob: 1fdfa95fd39007e40faf5956a00afb56216c0646 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
|
// 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.devtools.build.lib.analysis.config.BuildOptions;
/**
* Interface for a configuration transition.
*
* <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 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:
*
* <pre>
* 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;
* }
* }
* </pre>
*
* <p>For performance reasons, the input options are passed as a <i>reference</i>, not a
* <i>copy</i>. Implementations should <i>always</i> 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.
*/
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);
}
|
