src/common/get-file-info.js/getFileParser
function getFileParser(resolvedConfig, filePath, plugins) {
  if (resolvedConfig && resolvedConfig.parser) {
    return resolvedConfig.parser;
  }

  const inferredParser = options.inferParser(filePath, plugins);

  if (inferredParser) {
    return inferredParser;
  }

  return null;
}