src/main/java/com/google/devtools/build/skyframe/TaggedEvents.java

// 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.annotations.VisibleForTesting;
import com.google.common.collect.Collections2;
import com.google.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableList;
import com.google.devtools.build.lib.events.Event;
import java.io.Serializable;
import java.util.Objects;
import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;

/**
 * A wrapper of {@link Event} that contains a tag of the label where the event was generated. This
 * class allows us to tell where the events are coming from when we group all the tags in a
 * NestedSet.
 *
 * <p>The only usage of this code for now is to be able to use --output_filter in Skyframe
 *
 * <p>This is intended only for use in alternative {@code MemoizingEvaluator} implementations.
 */
@Immutable
public final class TaggedEvents implements Serializable {
  private final ImmutableList<Event> events;
  private final int hashCode;

  @VisibleForTesting
  public TaggedEvents(final @Nullable String tag, ImmutableCollection<Event> events) {
    this.events =
        events.isEmpty()
            ? ImmutableList.of()
            : ImmutableList.copyOf(
                Collections2.transform(
                    events,
                    (Event e) -> e.withTag(tag)));
    this.hashCode = events.hashCode();
  }

  ImmutableList<Event> getEvents() {
    return events;
  }

  /**
   * Returns <i>some</i> moderately sane representation of the events. Should never be used in
   * user-visible places, only for debugging and testing.
   */
  @Override
  public String toString() {
    return events.toString();
  }

  @Override
  public int hashCode() {
    return hashCode;
  }

  @Override
  public boolean equals(Object other) {
    if (this == other) {
      return true;
    }
    if (!(other instanceof TaggedEvents)) {
      return false;
    }
    TaggedEvents that = (TaggedEvents) other;
    return (hashCode == that.hashCode) && Objects.equals(this.events, that.events);
  }
}