Update from Google.
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MOE_MIGRATED_REVID=85702957
diff --git a/src/main/java/com/google/devtools/build/skyframe/CyclesReporter.java b/src/main/java/com/google/devtools/build/skyframe/CyclesReporter.java
new file mode 100644
index 0000000..a9b0d8e
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/skyframe/CyclesReporter.java
@@ -0,0 +1,102 @@
+// 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.skyframe;
+
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
+import com.google.devtools.build.lib.events.EventHandler;
+
+/**
+ * An utility for custom reporting of errors from cycles in the the Skyframe graph. This class is
+ * stateful in order to differentiate between new cycles and cycles that have already been
+ * reported (do not reuse the instances or cache the results as it could end up printing
+ * inconsistent information or leak memory). It treats two cycles as the same if they contain the
+ * same {@link SkyKey}s in the same order, but perhaps with different starting points. See
+ * {@link CycleDeduper} for more information.
+ */
+public class CyclesReporter {
+
+ /**
+ * Interface for reporting custom information about a single cycle.
+ */
+ public interface SingleCycleReporter {
+
+ /**
+ * Reports the given cycle and returns {@code true}, or return {@code false} if this
+ * {@link SingleCycleReporter} doesn't know how to report the cycle.
+ *
+ * @param topLevelKey the top level key that transitively depended on the cycle
+ * @param cycleInfo the cycle
+ * @param alreadyReported whether the cycle has already been reported to the
+ * {@link CyclesReporter}.
+ * @param eventHandler the eventHandler to which to report the error
+ */
+ boolean maybeReportCycle(SkyKey topLevelKey, CycleInfo cycleInfo, boolean alreadyReported,
+ EventHandler eventHandler);
+ }
+
+ private final ImmutableList<SingleCycleReporter> cycleReporters;
+ private final CycleDeduper<SkyKey> cycleDeduper = new CycleDeduper<>();
+
+ /**
+ * Constructs a {@link CyclesReporter} that delegates to the given {@link SingleCycleReporter}s,
+ * in the given order, to report custom information about cycles.
+ */
+ public CyclesReporter(SingleCycleReporter... cycleReporters) {
+ this.cycleReporters = ImmutableList.copyOf(cycleReporters);
+ }
+
+ /**
+ * Reports the given cycles, differentiating between cycles that have already been reported.
+ *
+ * @param cycles The {@code Iterable} of cycles.
+ * @param topLevelKey This key represents the top level value key that returned cycle errors.
+ * @param eventHandler the eventHandler to which to report the error
+ */
+ public void reportCycles(Iterable<CycleInfo> cycles, SkyKey topLevelKey,
+ EventHandler eventHandler) {
+ Preconditions.checkNotNull(eventHandler);
+ for (CycleInfo cycleInfo : cycles) {
+ boolean alreadyReported = false;
+ if (!cycleDeduper.seen(cycleInfo.getCycle())) {
+ alreadyReported = true;
+ }
+ boolean successfullyReported = false;
+ for (SingleCycleReporter cycleReporter : cycleReporters) {
+ if (cycleReporter.maybeReportCycle(topLevelKey, cycleInfo, alreadyReported, eventHandler)) {
+ successfullyReported = true;
+ break;
+ }
+ }
+ Preconditions.checkState(successfullyReported,
+ printArbitraryCycle(topLevelKey, cycleInfo, alreadyReported));
+ }
+ }
+
+ private String printArbitraryCycle(SkyKey topLevelKey, CycleInfo cycleInfo,
+ boolean alreadyReported) {
+ StringBuilder cycleMessage = new StringBuilder()
+ .append("topLevelKey: " + topLevelKey + "\n")
+ .append("alreadyReported: " + alreadyReported + "\n")
+ .append("path to cycle:\n");
+ for (SkyKey skyKey : cycleInfo.getPathToCycle()) {
+ cycleMessage.append(skyKey + "\n");
+ }
+ cycleMessage.append("cycle:\n");
+ for (SkyKey skyKey : cycleInfo.getCycle()) {
+ cycleMessage.append(skyKey + "\n");
+ }
+ return cycleMessage.toString();
+ }
+}
