code: function loadIconsFromDiskCache (loader, query, cacheFile, fileHash, callback) {
    // Stop if cache is disabled
    if (!query.persistentCache) return callback(null);
    var resolvedCacheFile = path.resolve(loader._compiler.parentCompilation.compiler.outputPath, cacheFile);
  
    fs.exists(resolvedCacheFile, function (exists) {
      if (!exists) return callback(null);
      fs.readFile(resolvedCacheFile, function (err, content) {
        if (err) return callback(err);
        var cache;
        try {
          cache = JSON.parse(content);
          // Bail out if the file or the option changed
          if (!isCacheValid(cache, fileHash, query)) {
            return callback(null);
          }
        } catch (e) {
          return callback(e);
        }
        callback(null, cache.result);
      });
    });
  }
docs: Try to load the file from the disc cache