workbox-precache caches error responses

Hi

Library Affected: workbox-precache

Browser & Platform: Google Chrome latest

Issue or Feature Request Description:

Workbox precache module caches 404 error response, but it shouldn’t, See screenshot:

Using workbox 6.0.2

My sw.js

const precacheUrls = self.__WB_MANIFEST;
if (precacheUrls) {
  precacheAndRoute(precacheUrls);
}

[jeffposnick]

This is now fixed in the v6.1.0 release.

[jeffposnick]

Ah, thank you for sharing all those steps. I believe this is a regression due to some changes in our precaching logic introduced in Workbox v6:

https://github.com/GoogleChrome/workbox/blob/590d1264f57392b1feb538440858f20a52fe6fdf/packages/workbox-precaching/src/PrecacheStrategy.ts#L142-L166

That const response = await handler.fetchAndCachePut(request) line should just be a handler.fetch(), and the handler.cachePut() should be deferred until after the responseSafeToPrecache result is confirmed to be true. In the current implementation, we’re ending up saving entries to the cache and failing the current install, but the next install attempt succeeds (because we don’t attempt to re-cache entries that are already cached unless their revision has changed).

I’ll get a fix out for this targeted for the upcoming 6.1.0 release. Thanks for pointing it out!

CC: @philipwalton