Allow Skylark import lookup values to be computed inline in order to avoid reifying them in the Skyframe graph.

--
MOS_MIGRATED_REVID=103758591

1 files changed, 41 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/CycleUtils.java b/src/main/java/com/google/devtools/build/lib/skyframe/CycleUtils.java
new file mode 100644
index 0000000000..c765ddf767
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/CycleUtils.java
@@ -0,0 +1,41 @@
+// Copyright 2015 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.skyframe;
+
+import com.google.common.base.Predicate;
+import com.google.common.collect.ImmutableList;
+import com.google.devtools.build.lib.util.Pair;
+
+/** Simple utility for separating path and cycle from a combined iterable. */
+class CycleUtils {
+  private CycleUtils() {}
+
+  static <S> Pair<ImmutableList<S>, ImmutableList<S>> splitIntoPathAndChain(
+      Predicate<S> startOfCycle, Iterable<S> pathAndCycle) {
+    boolean inPathToCycle = true;
+    ImmutableList.Builder<S> pathToCycleBuilder = ImmutableList.builder();
+    ImmutableList.Builder<S> cycleBuilder = ImmutableList.builder();
+    for (S elt : pathAndCycle) {
+      if (startOfCycle.apply(elt)) {
+        inPathToCycle = false;
+      }
+      if (inPathToCycle) {
+        pathToCycleBuilder.add(elt);
+      } else {
+        cycleBuilder.add(elt);
+      }
+    }
+    return Pair.of(pathToCycleBuilder.build(), cycleBuilder.build());
+  }
+}