src/main/java/com/google/devtools/build/lib/actions/cache/MetadataHandler.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.actions.cache;

import com.google.common.collect.ImmutableSet;
import com.google.devtools.build.lib.actions.Artifact;
import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
import com.google.devtools.build.lib.actions.FileArtifactValue;
import com.google.devtools.build.lib.actions.MetadataProvider;
import com.google.devtools.build.lib.vfs.FileStatus;
import java.io.IOException;

/**
 * Retrieves {@link FileArtifactValue} of {@link Artifact}s, and inserts virtual metadata as well.
 *
 * <p>Some methods on this interface may only be called after a call to {@link
 * #discardOutputMetadata}. Calling them before such a call results in an {@link
 * IllegalStateException}.
 *
 * <p>Note that implementations of this interface call chmod on output files if {@link
 * #discardOutputMetadata} has been called.
 */
public interface MetadataHandler extends MetadataProvider, MetadataInjector {

  /** Sets digest for virtual artifacts (e.g. middlemen). {@code digest} must not be null. */
  void setDigestForVirtualArtifact(Artifact artifact, byte[] digest);

  /**
   * Constructs a {@link FileArtifactValue} for the given output whose digest is known.
   *
   * <p>This call does not inject the returned metadata. It should be injected with a followup call
   * to {@link #injectFile} or {@link #injectDirectory} as appropriate.
   *
   * <p>chmod will not be called on the output.
   */
  FileArtifactValue constructMetadataForDigest(
      Artifact output, FileStatus statNoFollow, byte[] injectedDigest) throws IOException;

  /** Retrieves the artifacts inside the TreeArtifact, without injecting its digest. */
  ImmutableSet<TreeFileArtifact> getExpandedOutputs(Artifact artifact);

  /**
   * Returns true iff artifact was intentionally omitted (not saved).
   */
  // TODO(ulfjack): artifactOmitted always returns false unless we've just executed the action, and
  // made calls to markOmitted. We either need to document that or change it so it works reliably.
  boolean artifactOmitted(Artifact artifact);

  /**
   * Discards all known output artifact metadata, presumably because outputs will be modified. May
   * only be called before any metadata is injected.
   *
   * <p>Must be called at most once on any specific instance.
   */
  void discardOutputMetadata();

  /**
   * Discards output artifact metadata and removes them from other data structures. Use this if an
   * action can make multiple attempts that are expected to create the same set of output files.
   */
  void resetOutputs(Iterable<Artifact> outputs);
}