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// Copyright 2014 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.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.devtools.build.lib.events.ExtendedEventHandler;
/**
* 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,
ExtendedEventHandler 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, ExtendedEventHandler 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();
}
}
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