Can't pass credentials when precaching routes

[mnquintana]

Library Affected:
workbox-precaching@3.0.0-beta.0

Browser & Platform:
All browsers

Issue or Feature Request Description:
Currently workbox.precache isn't passing credentials along when fetching assets, which means that any requests that require, say, a valid cookie, will fail. 😢

It looks like this is because the PrecacheController is explicitly passing in null for fetchOptions to the fetchWrapper:

workbox/packages/workbox-precaching/controllers/PrecacheController.mjs

Lines 207 to 211 in 08d323e

	let response = await fetchWrapper.fetch(
	precacheEntry._networkRequest,
	null,
	plugins,
	);

What I'd like to see is an API to pass fetchOptions down to the fetch wrapper, potentially on a per route / asset basis.

Steps to Reproduce

1. Create a precache manifest entry pointing to an asset that can only be accessed with a cookie
2. workbox.precache.precacheAndRoute(...)
3. Load the page and wait for the Service Worker to activate
4. Fetching the asset will fail

Let me know if there's any more info I could provide that'd be helpful! 🙇

[jeffposnick]

Thanks for reporting this!

We hardcoded same-origin for precaching in the previous Workbox release (and in sw-precache), and it seemed to be non-controversial. Here's the v2 code:

workbox/packages/workbox-precaching/src/lib/controllers/base-cache-manager.js

Lines 28 to 35 in 60d9026

	this._requestWrapper = new RequestWrapper({
	cacheName,
	cacheId,
	plugins,
	fetchOptions: {
	credentials: 'same-origin',
	},
	});

@gauntface, I'll put together a PR to add this in to v3, unless you're aware of why we wouldn't want to do this anymore.