src/main/java/com/google/devtools/build/lib/skyframe/SkylarkImportUniqueCycleFunction.java


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// Copyright 2015 Google Inc. 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.skyframe;

import com.google.devtools.build.lib.cmdline.PackageIdentifier;
import com.google.devtools.build.skyframe.SkyKey;
import com.google.devtools.build.skyframe.SkyValue;

/**
 * Emits an error message exactly once when a Skylark import cycle is found when running inlined
 * {@link SkylarkImportLookupFunction}s.
 */
class SkylarkImportUniqueCycleFunction extends AbstractChainUniquenessFunction<SkyKey> {
  private static final SkyValue INSTANCE = new SkyValue() {};

  @Override
  protected String getConciseDescription() {
    return "cycle in referenced extension files";
  }

  @Override
  protected String getHeaderMessage() {
    return "";
  }

  @Override
  protected String getFooterMessage() {
    return "";
  }

  @Override
  protected SkyValue getDummyValue() {
    return INSTANCE;
  }

  @Override
  protected String elementToString(SkyKey elt) {
    PackageIdentifier pkgId = (PackageIdentifier) elt.argument();
    return pkgId.getPathFragment().getPathString();
  }
}