src/main/java/com/google/devtools/build/lib/analysis/WrappingProviderHelper.java

// Copyright 2017 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 java.util.ArrayList;
import java.util.List;
import javax.annotation.Nullable;

/** Helper methods for {@link WrappingProvider} */
public class WrappingProviderHelper {

  private WrappingProviderHelper() {}

  /** Gets the actual providers from a list of wrappers. */
  public static <T extends TransitiveInfoProvider> List<T> unwrapProviders(
      Iterable<? extends WrappingProvider> wrappingProviders, Class<T> providerClass) {
    List<T> result = new ArrayList<>();
    for (WrappingProvider wrappingProvider : wrappingProviders) {
      T provider = wrappingProvider.getTransitiveInfoProviderMap().getProvider(providerClass);
      if (provider != null) {
        result.add(provider);
      }
    }
    return result;
  }

  /** Reads a provider via a wrapping provider. Returns null if not wrapped. */
  @Nullable
  public static <T extends TransitiveInfoProvider, U extends WrappingProvider> T getWrappedProvider(
      TransitiveInfoCollection collection, Class<U> wrappingProviderClass, Class<T> providerClass) {
    WrappingProvider wrappingProvider = collection.getProvider(wrappingProviderClass);
    if (wrappingProvider != null) {
      return wrappingProvider.getTransitiveInfoProviderMap().getProvider(providerClass);
    }
    return null;
  }
}