java/com/google/gitiles/VisibilityChecker.java

// Copyright 2019 Google LLC
//
// 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
//
//     https://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.gitiles;

import com.google.common.collect.ImmutableList;
import java.io.IOException;
import java.util.stream.Stream;
import org.eclipse.jgit.annotations.Nullable;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.RefDatabase;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevWalk;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Checks for object visibility
 *
 * <p>Objects are visible if they are reachable from any of the references visible to the user.
 */
public class VisibilityChecker {

  private static final Logger log = LoggerFactory.getLogger(VisibilityChecker.class);

  /**
   * Check if any of the refs in {@code refDb} points to the object {@code id}.
   *
   * @param refDb a reference database
   * @param id object we are looking for
   * @return true if the any of the references in the db points directly to the id
   * @throws IOException the reference space cannot be accessed
   */
  protected boolean isTipOfBranch(RefDatabase refDb, ObjectId id) throws IOException {
    // If any reference directly points at the requested object, permit display. Common for displays
    // of pending patch sets in Gerrit Code Review, or bookmarks to the commit a tag points at.
    return !refDb.getTipsWithSha1(id).isEmpty();
  }

  /**
   * Check if {@code commit} is reachable starting from {@code starters}.
   *
   * @param walk The walk to use for the reachability check
   * @param commit The starting commit. It *MUST* come from the walk in use
   * @param starters visible commits. Anything reachable from these commits is visible. Missing ids
   *     or ids referring to other kinds of objects are ignored.
   * @return true if we can get to {@code commit} from the {@code starters}
   * @throws IOException a pack file or loose object could not be read
   */
  protected boolean isReachableFrom(RevWalk walk, RevCommit commit, Stream<RevCommit> starters)
      throws IOException {
    return walk.getObjectReader()
        .createReachabilityChecker(walk)
        .areAllReachable(ImmutableList.of(commit), starters)
        .isEmpty();
  }

  @Nullable
  static RevCommit objectIdToRevCommit(RevWalk walk, ObjectId objectId) {
    if (objectId == null) {
      return null;
    }

    try {
      return walk.parseCommit(objectId);
    } catch (IOException e) {
      log.warn("Cannot translate %s to RevCommit: %s", objectId.name(), e.getMessage());
      return null;
    }
  }
}