Minor change to add QueryableGraphBackedSkyFunctionEnvironment.

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MOS_MIGRATED_REVID=125362963
diff --git a/src/main/java/com/google/devtools/build/skyframe/QueryableGraphBackedSkyFunctionEnvironment.java b/src/main/java/com/google/devtools/build/skyframe/QueryableGraphBackedSkyFunctionEnvironment.java
new file mode 100644
index 0000000..c9d33a4
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/skyframe/QueryableGraphBackedSkyFunctionEnvironment.java
@@ -0,0 +1,90 @@
+// Copyright 2016 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 com.google.common.base.Function;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Maps;
+import com.google.common.collect.Sets;
+import com.google.devtools.build.lib.events.EventHandler;
+import com.google.devtools.build.lib.util.Preconditions;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+
+import javax.annotation.Nullable;
+
+/**
+ * A {@link SkyFunction.Environment} backed by a {@link QueryableGraph}. For use when a single
+ * SkyFunction needs recomputation, and its dependencies do not need to be evaluated. Any missing
+ * dependencies will be ignored.
+ */
+public class QueryableGraphBackedSkyFunctionEnvironment extends AbstractSkyFunctionEnvironment {
+  private final QueryableGraph queryableGraph;
+  private final EventHandler eventHandler;
+
+  public QueryableGraphBackedSkyFunctionEnvironment(
+      QueryableGraph queryableGraph, EventHandler eventHandler) {
+    this.queryableGraph = queryableGraph;
+    this.eventHandler = eventHandler;
+  }
+
+  private static final Function<NodeEntry, ValueOrUntypedException> NODE_ENTRY_TO_UNTYPED_VALUE =
+      new Function<NodeEntry, ValueOrUntypedException>() {
+        @Override
+        public ValueOrUntypedException apply(@Nullable NodeEntry nodeEntry) {
+          if (nodeEntry == null || !nodeEntry.isDone()) {
+            return ValueOrExceptionUtils.ofNull();
+          }
+          SkyValue maybeWrappedValue = nodeEntry.getValueMaybeWithMetadata();
+          SkyValue justValue = ValueWithMetadata.justValue(maybeWrappedValue);
+          if (justValue != null) {
+            return ValueOrExceptionUtils.ofValueUntyped(justValue);
+          }
+          ErrorInfo errorInfo =
+              Preconditions.checkNotNull(ValueWithMetadata.getMaybeErrorInfo(maybeWrappedValue));
+          Exception exception = errorInfo.getException();
+
+          if (exception != null) {
+            // Give SkyFunction#compute a chance to handle this exception.
+            return ValueOrExceptionUtils.ofExn(exception);
+          }
+          // In a cycle.
+          Preconditions.checkState(
+              !Iterables.isEmpty(errorInfo.getCycleInfo()), "%s %s", errorInfo, maybeWrappedValue);
+          return ValueOrExceptionUtils.ofNull();
+        }
+      };
+
+  @Override
+  protected Map<SkyKey, ValueOrUntypedException> getValueOrUntypedExceptions(Set<SkyKey> depKeys) {
+    Map<SkyKey, NodeEntry> resultMap = queryableGraph.getBatch(depKeys);
+    Map<SkyKey, NodeEntry> resultWithMissingKeys = new HashMap<>(resultMap);
+    for (SkyKey missingDep : Sets.difference(depKeys, resultMap.keySet())) {
+      resultWithMissingKeys.put(missingDep, null);
+    }
+    return Maps.transformValues(resultWithMissingKeys, NODE_ENTRY_TO_UNTYPED_VALUE);
+  }
+
+  @Override
+  public EventHandler getListener() {
+    return eventHandler;
+  }
+
+  @Override
+  public boolean inErrorBubblingForTesting() {
+    return false;
+  }
+}