Function readCompressedJsonFileFallbackLazily

lib/read-json-file.js:40–78

(xpath)

// Wrapper on readCompressedJsonFileFallback that initially only checks
// if the file exists but doesn't read the content till you call it.
export function readCompressedJsonFileFallbackLazily(xpath) {
  const cache = new Map()
  // This will throw if the file isn't accessible at all, e.g. ENOENT
  // But, the file might have been replaced by one called `SAMENAME.json.br`
  // because in staging, we ship these files compressed to make the
  // deployment faster. So, in our file-presence check, we need to
  // account for that.
  try {
    fs.accessSync(xpath)
  } catch (err) {
    if (err.code === 'ENOENT') {
      try {
        fs.accessSync(xpath + '.br')
      } catch (err) {
        if (err.code === 'ENOENT') {
          throw new Error(`Neither ${xpath} nor ${xpath}.br is accessible`)
        }
        throw err
      }
    } else {
      throw err
    }
  }
  return () => {
    if (!cache.has(xpath)) {
      cache.set(xpath, readCompressedJsonFileFallback(xpath))
      if (globalCacheCounter[xpath]) {
        console.warn(
          "If this happens it's because the readCompressedJsonFileFallbackLazily " +
            'function has been called non-globally. Only use ' +
            'readCompressedJsonFileFallback once at module-level.'
        )
        throw new Error(`Globally reading the same file more than once (${xpath})`)
      }
      globalCacheCounter[xpath] = 1
    }
    return cache.get(xpath)
  }
}