1 files changed, 130 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/AbstractLabelCycleReporter.java b/src/main/java/com/google/devtools/build/lib/skyframe/AbstractLabelCycleReporter.java
new file mode 100644
index 0000000000..797f15867e
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/AbstractLabelCycleReporter.java
@@ -0,0 +1,130 @@
+// 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.skyframe;
+
+import com.google.common.base.Function;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.events.Event;
+import com.google.devtools.build.lib.events.EventHandler;
+import com.google.devtools.build.lib.packages.NoSuchThingException;
+import com.google.devtools.build.lib.packages.Target;
+import com.google.devtools.build.lib.pkgcache.LoadedPackageProvider;
+import com.google.devtools.build.lib.syntax.Label;
+import com.google.devtools.build.skyframe.CycleInfo;
+import com.google.devtools.build.skyframe.CyclesReporter;
+import com.google.devtools.build.skyframe.SkyKey;
+
+/** Reports cycles between skyframe values whose keys contains {@link Label}s. */
+abstract class AbstractLabelCycleReporter implements CyclesReporter.SingleCycleReporter {
+
+  private final LoadedPackageProvider loadedPackageProvider;
+
+  AbstractLabelCycleReporter(LoadedPackageProvider loadedPackageProvider) {
+    this.loadedPackageProvider = loadedPackageProvider;
+  }
+
+  /** Returns the String representation of the {@code SkyKey}. */
+  protected abstract String prettyPrint(SkyKey key);
+
+  /** Returns the associated Label of the SkyKey. */
+  protected abstract Label getLabel(SkyKey key);
+
+  protected abstract boolean canReportCycle(SkyKey topLevelKey, CycleInfo cycleInfo);
+
+  protected String getAdditionalMessageAboutCycle(SkyKey topLevelKey, CycleInfo cycleInfo) {
+    return "";
+  }
+
+  @Override
+  public boolean maybeReportCycle(SkyKey topLevelKey, CycleInfo cycleInfo,
+      boolean alreadyReported, EventHandler eventHandler) {
+    Preconditions.checkNotNull(eventHandler);
+    if (!canReportCycle(topLevelKey, cycleInfo)) {
+      return false;
+    }
+
+    if (alreadyReported) {
+      Label label = getLabel(topLevelKey);
+      Target target = getTargetForLabel(label);
+      eventHandler.handle(Event.error(target.getLocation(),
+          "in " + target.getTargetKind() + " " + label +
+              ": cycle in dependency graph: target depends on an already-reported cycle"));
+    } else {
+      StringBuilder cycleMessage = new StringBuilder("cycle in dependency graph:");
+      ImmutableList<SkyKey> pathToCycle = cycleInfo.getPathToCycle();
+      ImmutableList<SkyKey> cycle = cycleInfo.getCycle();
+      for (SkyKey value : pathToCycle) {
+        cycleMessage.append("\n    ");
+        cycleMessage.append(prettyPrint(value));
+      }
+
+      SkyKey cycleValue = printCycle(cycle, cycleMessage, new Function<SkyKey, String>() {
+        @Override
+        public String apply(SkyKey input) {
+          return prettyPrint(input);
+        }
+      });
+
+      cycleMessage.append(getAdditionalMessageAboutCycle(topLevelKey, cycleInfo));
+
+      Label label = getLabel(cycleValue);
+      Target target = getTargetForLabel(label);
+      eventHandler.handle(
+          Event.error(target.getLocation(), "in " + target.getTargetKind() + " " + label
+              + ": " + cycleMessage.toString()));
+    }
+
+    return true;
+  }
+
+  /**
+   * Prints the SkyKey-s in cycle into cycleMessage using the print function.
+   */
+  static SkyKey printCycle(ImmutableList<SkyKey> cycle, StringBuilder cycleMessage,
+      Function<SkyKey, String> printFunction) {
+    Iterable<SkyKey> valuesToPrint = cycle.size() > 1
+        ? Iterables.concat(cycle, ImmutableList.of(cycle.get(0))) : cycle;
+    SkyKey cycleValue = null;
+    for (SkyKey value : valuesToPrint) {
+      if (cycleValue == null) {
+        cycleValue = value;
+      }
+      if (value == cycleValue) {
+        cycleMessage.append("\n  * ");
+      } else {
+        cycleMessage.append("\n    ");
+      }
+      cycleMessage.append(printFunction.apply(value));
+    }
+
+    if (cycle.size() == 1) {
+      cycleMessage.append(" [self-edge]");
+    }
+
+    return cycleValue;
+  }
+
+  protected final Target getTargetForLabel(Label label) {
+    try {
+      return loadedPackageProvider.getLoadedTarget(label);
+    } catch (NoSuchThingException e) {
+      // This method is used for getting the target from a label in a circular dependency.
+      // If we have a cycle that means that we need to have accessed the target (to get its
+      // dependencies). So all the labels in a dependency cycle need to exist.
+      throw new IllegalStateException(e);
+    }
+  }
+}