src/main/java/com/google/devtools/build/lib/analysis/LanguageDependentFragment.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.lib.analysis;

import com.google.common.collect.ImmutableSet;
import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
import java.util.Objects;

/**
 * Transitive info provider for rules that behave differently when used from
 * different languages.
 *
 * <p>Most rules generate code for a particular language or are totally language independent.
 * Some rules, however, behave differently when depended upon from different languages.
 * They might generate different libraries when used from different languages (and with
 * different API versions). This interface allows code sharing between implementations.
 *
 * <p>This provider is not really a roll-up of transitive information.
 */
@Immutable
@AutoCodec
public final class LanguageDependentFragment implements TransitiveInfoProvider {
  /**
   * A language that can be supported by a multi-language configured target.
   *
   * <p>Note that no {@code hashCode}/{@code equals} methods are provided, because these
   * objects are expected to be compared for object identity, which is the default.
   */
  @AutoCodec
  public static final class LibraryLanguage {
    private final String displayName;

    @AutoCodec.Instantiator
    public LibraryLanguage(String displayName) {
      this.displayName = displayName;
    }

    @Override
    public String toString() {
      return displayName;
    }

    @Override
    public boolean equals(Object other) {
      if (!(other instanceof LibraryLanguage)) {
        return false;
      }
      LibraryLanguage otherLanguage = (LibraryLanguage) other;
      return Objects.equals(displayName, otherLanguage.displayName);
    }

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

  private final ImmutableSet<LibraryLanguage> languages;

  @AutoCodec.Instantiator
  public LanguageDependentFragment(ImmutableSet<LibraryLanguage> languages) {
    this.languages = languages;
  }

  /**
   * Returns a set of the languages the ConfiguredTarget generates output for.
   * For use only by rules that directly depend on this library via a "deps" attribute.
   */
  public ImmutableSet<LibraryLanguage> getSupportedLanguages() {
    return languages;
  }
}