code: @GwtIncompatible("Unnecessary")
    private void outputStringMap() throws IOException {
      if (!config.stringMapOutputPath.isEmpty()) {
        if (compiler.getStringMap() == null) {
          // Ensure an empty file is created if there is no string map.
          // This avoids confusing some build tools that expect to see the file, even if it is empty.
          if (!(new File(config.stringMapOutputPath).createNewFile())) {
            throw new IOException("Could not create file: " + config.stringMapOutputPath);
          }
        } else {
          compiler.getStringMap().save(config.stringMapOutputPath);
        }
      }
    }
docs: Outputs the string map generated by the {@link ReplaceStrings} pass if an output path exists.