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Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs.

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/*
 * Copyright 2019 The Closure Compiler Authors.
 *
 * 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.javascript.jscomp.diagnostic;

import static java.nio.charset.StandardCharsets.UTF_8;

import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.FormatMethod;
import com.google.errorprone.annotations.FormatString;
import com.google.errorprone.annotations.MustBeClosed;
import com.google.gson.stream.JsonWriter;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CodingErrorAction;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.function.Supplier;

/**
 * An implementation that adapts a {@link BufferedWriter} and writes to a real file.
 *
 * This class is designed to be super-sourceable by J2CL, since JS environments often don't have
 * file APIs. Doing so enables logging statements to be checked-in.
 */
final class WritingLogFile extends LogFile {

  @MustBeClosed
  static LogFile create(Path file) {
    try {
      Path dir = file.getParent();
      Files.createDirectories(dir);
      CharsetEncoder encoder = UTF_8.newEncoder();
      // Allow the logged string to contain invalid Unicode (replace invalid character sequences
      // but don't throw). This is useful in cases where the source code contains invalid Unicode
      // (e.g., inside strings).
      encoder
          .onMalformedInput(CodingErrorAction.REPLACE)
          .onUnmappableCharacter(CodingErrorAction.REPLACE);
      return new WritingLogFile(
          new BufferedWriter(
              new OutputStreamWriter(
                  Files.newOutputStream(
                      file,
                      StandardOpenOption.CREATE,
                      StandardOpenOption.APPEND,
                      StandardOpenOption.WRITE),
                  encoder)));
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }

  private final BufferedWriter writer;

  private WritingLogFile(BufferedWriter writer) {
    this.writer = writer;
  }

  @Override
  public LogFile log(Object value) {
    return logInternal(value.toString());
  }

  @Override
  public LogFile log(String value) {
    return logInternal(value);
  }

  @Override
  public LogFile log(Supplier value) {
    return logInternal(value.get());
  }

  @Override
  @FormatMethod
  public LogFile log(@FormatString String template, Object... values) {
    return logInternal(String.format(template, values));
  }

  @Override
  public LogFile logJson(Object value) {
    return logInternal(LogsGson.toJson(value));
  }

  @Override
  public LogFile logJson(Supplier