src/main/java/com/google/devtools/build/lib/pkgcache/LoadedPackageProvider.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.pkgcache;

import com.google.common.annotations.VisibleForTesting;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.concurrent.Uninterruptibles;
import com.google.devtools.build.lib.events.EventHandler;
import com.google.devtools.build.lib.packages.NoSuchPackageException;
import com.google.devtools.build.lib.packages.NoSuchTargetException;
import com.google.devtools.build.lib.packages.Target;

import java.util.concurrent.Callable;

/**
 * Read-only API for retrieving packages, i.e., calling this API should not result in packages being
 * loaded.
 *
 * <p><b>Concurrency</b>: Implementations should be thread-safe.
 */
// TODO(bazel-team): Skyframe doesn't really implement this - can we remove it?
public interface LoadedPackageProvider {

  /**
   * Returns a target if it was recently loaded, i.e., since the most recent cache sync. This
   * throws an exception if the target was not loaded or not validated, even if it exists in the
   * surrounding package. If the surrounding package is in error, still attempts to retrieve the
   * target.
   */
  Target getLoadedTarget(Label label) throws NoSuchPackageException, NoSuchTargetException;

  /**
   * A bridge class that implements the legacy semantics of {@link #getLoadedTarget} using a
   * normal {@link PackageProvider} instance.
   */
  public static final class Bridge implements LoadedPackageProvider {
    private final PackageProvider packageProvider;
    private final EventHandler eventHandler;

    public Bridge(PackageProvider packageProvider, EventHandler eventHandler) {
      this.packageProvider = packageProvider;
      this.eventHandler = eventHandler;
    }

    @Override
    public Target getLoadedTarget(Label label)
        throws NoSuchPackageException, NoSuchTargetException {
      return getLoadedTarget(packageProvider, eventHandler, label);
    }

    /**
     * Uninterruptible method to convert a label into a target using a given package provider and
     * event handler.
     */
    @VisibleForTesting
    public static Target getLoadedTarget(
        final PackageProvider packageProvider, final EventHandler eventHandler, final Label label)
            throws NoSuchPackageException, NoSuchTargetException {
      try {
        return Uninterruptibles.callUninterruptibly(new Callable<Target>() {
          @Override
          public Target call()
              throws NoSuchPackageException, NoSuchTargetException, InterruptedException {
            return packageProvider.getTarget(eventHandler, label);
          }
        });
      } catch (NoSuchPackageException | NoSuchTargetException e) {
        throw e;
      } catch (Exception e) {
        throw new IllegalStateException(e);
      }
    }
  }
}