matter() caches the content even when an error is thrown

[hankei6km]

It cancels throwing an error when processing the cached content.

Steps to reproduce

import matter from 'gray-matter';

const fixture = '---whatever\nABC: XYZ\n---';
console.log('=== start');
try {
  matter(fixture);
} catch (err) {
  console.log(`Error1: ${err}`);
}
console.log('===');
try {
  matter(fixture);
} catch (err) {
  console.log(`Error2: ${err}`);
}
console.log('=== done');

// === start
// Error1: Error: gray-matter engine "whatever" is not registered
// ===
// === done

Workaround

https://github.com/jonschlinkert/gray-matter/issues/43#issuecomment-318258919

  matter(fixture, {});

or

https://github.com/hankei6km/gray-matter/blob/cae943deb97562eed22c1ad4f29ac7e93527d864/index.js#L29

function matter(input, options) {
  if (input === '') {
    return { data: {}, content: input, excerpt: '', orig: input };
  }

  let file = toFile(input);
  const cached = matter.cache[file.content];

  if (!options) {
    if (cached) {
      file = Object.assign({}, cached);
      file.orig = cached.orig;
      return file;
    }

    const ret = parseMatter(file, options);

    // only cache if there are no options passed. if we cache when options
    // are passed, we would need to also cache options values, which would
    // negate any performance benefits of caching
    matter.cache[file.content] = file;

    return ret;
  }

  return parseMatter(file, options);
}