1 files changed, 38 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/actions/ActionGraph.java b/src/main/java/com/google/devtools/build/lib/actions/ActionGraph.java
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index 0000000000..bb2b707989
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+++ b/src/main/java/com/google/devtools/build/lib/actions/ActionGraph.java
@@ -0,0 +1,38 @@
+// Copyright 2014 Google Inc. 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.actions;
+
+import javax.annotation.Nullable;
+
+/**
+ * An action graph.
+ *
+ * <p>Provides lookups of generating actions for artifacts.
+ */
+public interface ActionGraph {
+
+  /**
+   * Returns the Action that, when executed, gives rise to this file.
+   *
+   * <p>If this Artifact is a source file, null is returned. (We don't try to return a "no-op
+   * action" because that would require creating a new no-op Action for every source file, since
+   * each Action knows its outputs, so sharing all the no-ops is not an option.)
+   *
+   * <p>It's also possible for derived Artifacts to have null generating Actions when these actions
+   * are unknown.
+   */
+  @Nullable
+  Action getGeneratingAction(Artifact artifact);
+}