src/main/java/com/google/devtools/build/lib/skyframe/RepositoryMappingValue.java

// Copyright 2018 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.lib.skyframe;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Interner;
import com.google.devtools.build.lib.cmdline.RepositoryName;
import com.google.devtools.build.lib.concurrent.BlazeInterners;
import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
import com.google.devtools.build.skyframe.AbstractSkyKey;
import com.google.devtools.build.skyframe.SkyFunctionName;
import com.google.devtools.build.skyframe.SkyKey;
import com.google.devtools.build.skyframe.SkyValue;
import java.util.Objects;

/**
 * A value that represents the 'mappings' of an external Bazel workspace, as defined
 * in the main WORKSPACE file. The SkyValue contains the mappings themselves, with the key being
 * the name of the external repository.
 *
 * <p>Given the following rule:
 * <pre>{@code
 * local_repository(
 *   name = “a”,
 *   path = “../a”,
 *   repo_mapping = {“@x” : “@y”}
 * )
 * }</pre>
 *
 * <p>The SkyKey would be {@code "@a"} and the SkyValue would be the map {@code {"@x" : "@y"}}
 *
 * <p>This is kept as a separate value with trivial change pruning so as to not necessitate a
 * dependency from every {@link PackageValue} to the //external {@link PackageValue}, so that
 * changes to things in the WORKSPACE other than the mappings (and name) won't require reloading
 * all packages. If the mappings are changed then the external packages need to be reloaded.
 */
public class RepositoryMappingValue implements SkyValue {

  private final ImmutableMap<RepositoryName, RepositoryName> repositoryMapping;

  private RepositoryMappingValue(ImmutableMap<RepositoryName, RepositoryName> repositoryMapping) {
    Preconditions.checkNotNull(repositoryMapping);
    this.repositoryMapping = repositoryMapping;
  }

  /** Returns the workspace mappings. */
  public ImmutableMap<RepositoryName, RepositoryName> getRepositoryMapping() {
    return repositoryMapping;
  }

  /** Returns the {@link Key} for {@link RepositoryMappingValue}s. */
  public static Key key(RepositoryName repositoryName) {
    return RepositoryMappingValue.Key.create(repositoryName);
  }

  /** Returns a {@link RepositoryMappingValue} for a workspace with the given name. */
  public static RepositoryMappingValue withMapping(
      ImmutableMap<RepositoryName, RepositoryName> repositoryMapping) {
    return new RepositoryMappingValue(Preconditions.checkNotNull(repositoryMapping));
  }

  @Override
  public boolean equals(Object o) {
    if (!(o instanceof RepositoryMappingValue)) {
      return false;
    }
    RepositoryMappingValue other = (RepositoryMappingValue) o;
    return Objects.equals(repositoryMapping, other.repositoryMapping);
  }

  @Override
  public int hashCode() {
    return Objects.hash(repositoryMapping);
  }

  @Override
  public String toString() {
    return repositoryMapping.toString();
  }

  /** {@link SkyKey} for {@link RepositoryMappingValue}. */
  @AutoCodec.VisibleForSerialization
  @AutoCodec
  static class Key extends AbstractSkyKey<RepositoryName> {

    private static final Interner<Key> interner = BlazeInterners.newWeakInterner();

    private Key(RepositoryName arg) {
      super(arg);
    }

    @AutoCodec.VisibleForSerialization
    @AutoCodec.Instantiator
    static Key create(RepositoryName arg) {
      return interner.intern(new Key(arg));
    }

    @Override
    public SkyFunctionName functionName() {
      return SkyFunctions.REPOSITORY_MAPPING;
    }
  }
}