Adding a ConstantVersion to Skyframe, to be used when only a single evaluation of the graph with a single constant version is expected

RELNOTES: None
PiperOrigin-RevId: 164059941

1 files changed, 26 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/skyframe/ConstantVersion.java b/src/main/java/com/google/devtools/build/skyframe/ConstantVersion.java
new file mode 100644
index 0000000000..792f167a6f
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/skyframe/ConstantVersion.java
@@ -0,0 +1,26 @@
+// 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.skyframe;
+
+/** Use when only a single evaluation of the graph with a single constant version is expected. */
+public class ConstantVersion implements Version {
+  public static final ConstantVersion INSTANCE = new ConstantVersion();
+
+  private ConstantVersion() {}
+
+  @Override
+  public boolean atMost(Version other) {
+    return this.equals(other);
+  }
+}