| // Copyright 2014 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.skyframe; |
| |
| import java.io.Serializable; |
| import java.math.BigInteger; |
| import javax.annotation.Nullable; |
| |
| /** |
| * A return value of a {@code SkyFunction}. |
| */ |
| public interface SkyValue extends Serializable { |
| /** |
| * If non-null, a fingerprint for this value such that two values are equal iff they have the same |
| * fingerprint. For use during dep-fingerprint-based change pruning: see {@link |
| * NodeEntry#canPruneDepsByFingerprint}. |
| */ |
| @Nullable |
| default BigInteger getValueFingerprint() { |
| return null; |
| } |
| |
| /** |
| * Returns true for values that may compare objects that must be compared using reference |
| * equality. Such values may force re-evaluation of downstream nodes even if they evaluate to the |
| * same {@link Version} as before, since the downstream nodes may have reference-unequal objects |
| * from the previous evaluation. Under normal circumstances, a node can never re-evaluate to the |
| * same {@link Version}, so this doesn't come into play. |
| */ |
| default boolean mustBeReferenceComparedOnRecomputation() { |
| return false; |
| } |
| |
| /** |
| * Returns true for values that can be reused across builds. Some values are inherently "flaky", |
| * like test statuses or stamping information, and in certain circumstances, those values cannot |
| * be shared across builds/servers. |
| */ |
| default boolean dataIsShareable() { |
| return true; |
| } |
| } |