myapp/node_modules/make-fetch-happen/lib/cache/index.js

const { NotCachedError } = require('./errors.js')
const CacheEntry = require('./entry.js')
const remote = require('../remote.js')

// do whatever is necessary to get a Response and return it
const cacheFetch = async (request, options) => {
  // try to find a cached entry that satisfies this request
  const entry = await CacheEntry.find(request, options)
  if (!entry) {
    // no cached result, if the cache mode is 'only-if-cached' that's a failure
    if (options.cache === 'only-if-cached') {
      throw new NotCachedError(request.url)
    }

    // otherwise, we make a request, store it and return it
    const response = await remote(request, options)
    const newEntry = new CacheEntry({ request, response, options })
    return newEntry.store('miss')
  }

  // we have a cached response that satisfies this request, however if the cache
  // mode is 'no-cache' then we send the revalidation request no matter what
  if (options.cache === 'no-cache') {
    return entry.revalidate(request, options)
  }

  // if the cached entry is not stale, or if the cache mode is 'force-cache' or
  // 'only-if-cached' we can respond with the cached entry. set the status
  // based on the result of needsRevalidation and respond
  const _needsRevalidation = entry.policy.needsRevalidation(request)
  if (options.cache === 'force-cache' ||
      options.cache === 'only-if-cached' ||
      !_needsRevalidation) {
    return entry.respond(request.method, options, _needsRevalidation ? 'stale' : 'hit')
  }

  // if we got here, the cache entry is stale so revalidate it
  return entry.revalidate(request, options)
}

cacheFetch.invalidate = async (request, options) => {
  if (!options.cachePath) {
    return
  }

  return CacheEntry.invalidate(request, options)
}

module.exports = cacheFetch