src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkPrintable.java

// Copyright 2017 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.skylarkinterface;

/**
 * Interface for types that aren't {@link SkylarkValue}s, but that we still want to support printing
 * of.
 */
public interface SkylarkPrintable {

  /**
   * Prints an official representation of object x.
   *
   * <p>For regular data structures, the value should be parsable back into an equal data structure.
   *
   * @param printer a printer to be used for formatting nested values.
   */
  void repr(SkylarkPrinter printer);

  /**
   * Prints an informal, human-readable representation of the value.
   *
   * <p>By default dispatches to the {@code repr} method.
   *
   * @param printer a printer to be used for formatting nested values.
   */
  default void str(SkylarkPrinter printer) {
    repr(printer);
  }

  /**
   * Prints an informal debug representation of the value.
   *
   * <p>This debug representation is only ever printed to the terminal or to another out-of-band
   * channel, and is never accessible to Skylark code. Therefore, it is safe for the debug
   * representation to reveal properties of the value that are usually hidden for the sake of
   * performance, determinism, or forward-compatibility.
   *
   * <p>By default dispatches to the {@code str} method.
   *
   * @param printer a printer to be used for formatting nested values.
   */
  default void debugPrint(SkylarkPrinter printer) {
    str(printer);
  }
}