content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 org.apache.beam.sdk.util.construction;
  
  import java.util.Map;
  import org.apache.beam.sdk.coders.CannotProvideCoderException;
  import org.apache.beam.sdk.options.PipelineOptions;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.apache.beam.sdk.transforms.display.DisplayData;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.PInput;
  import org.apache.beam.sdk.values.POutput;
  import org.apache.beam.sdk.values.PValue;
  import org.apache.beam.sdk.values.TupleTag;
  
  /**
   * A base class for implementing {@link PTransform} overrides, which behave identically to the
   * delegate transform but with overridden methods. Implementors are required to implement {@link
   * #delegate()}, which returns the object to forward calls to, and {@link #expand(PInput)}.
   */
  @SuppressWarnings({
    "rawtypes", // TODO(https://github.com/apache/beam/issues/20447)
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public abstract class ForwardingPTransform<InputT extends PInput, OutputT extends POutput>
      extends PTransform<InputT, OutputT> {
    protected abstract PTransform<InputT, OutputT> delegate();
  
    @Override
    public OutputT expand(InputT input) {
      OutputT res = delegate().expand(input);
      if (res instanceof PCollection) {
        PCollection pc = (PCollection) res;
        try {
          pc.setCoder(delegate().getDefaultOutputCoder(input, pc));
        } catch (CannotProvideCoderException e) {
          // Let coder inference happen later.
        }
      }
      return res;
    }
  
    @Override
    public Map<TupleTag<?>, PValue> getAdditionalInputs() {
      return delegate().getAdditionalInputs();
    }
  
    @Override
    public void validate(PipelineOptions options) {
      delegate().validate(options);
    }
  
    @Override
    public String getName() {
      return delegate().getName();
    }
  
    @Override
    public void populateDisplayData(DisplayData.Builder builder) {
      builder.delegate(delegate());
    }
  }
  