/*
 * Copyright 2019-present Facebook, Inc.
 *
 * 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.facebook.buck.core.rules.attr;

import com.facebook.buck.core.rules.BuildRule;
import com.facebook.buck.core.sourcepath.SourcePath;
import com.google.common.collect.ImmutableMap;
import javax.annotation.Nullable;

/**
 * {@link com.facebook.buck.core.rules.BuildRule} instances that support multiple outputs via output
 * labels.
 */
public interface HasMultipleOutputs extends BuildRule {
  /**
   * Returns the {@link SourcePath} to the output associated with the given output label, or {@code
   * null} if it does not exist.
   */
  @Nullable
  SourcePath getSourcePathToOutput(String outputLabel);

  /** Returns a map of {@link SourcePath} instances keyed by associated output labels. */
  ImmutableMap<String, SourcePath> getSourcePathsByOutputsLabels();
}

@@ -790,16 +790,43 @@
 bleMap;%0A
+import java.util.Optional;%0A
 import j
@@ -1166,16 +1166,143 @@
 t exist.
+ If an empty output label is given, returns the default %7B@link%0A   * SourcePath%7D to the default output associated with the rule.
 %0A   */%0A 
@@ -1347,22 +1347,32 @@
 oOutput(
+Optional%3C
 String
+%3E
  outputL

Change HasMultipleOutputs#getSourcePathToOutput to take an Optional<String> instead of String