Workbox fails to initialize with incorrect cache key

[wallzero]

Library Affected:
[email protected], GenerateSW

Browser & Platform:
n/a

Issue or Feature Request Description:

Currently I receive the following browser error with my SPA setup:

Uncaught incorrect-type: The parameter 'cachedAssetUrl' passed into 'workbox-routing.registerNavigationRoute()' must be of type string.
    at Object.isType (http://localhost:8080/bundle/workbox/workbox-v4.3.1/workbox-core.dev.js:457:13)
    at Object.registerNavigationRoute (http://localhost:8080/bundle/workbox/workbox-v4.3.1/workbox-routing.dev.js:814:25)
    at http://localhost:8080/workbox.js:39:17

This is my current setup in webpack:

new GenerateSW({
        cacheId: 'any',
        directoryIndex: 'index.html',
        exclude: [/\.map($|\?)/, /\.gz$/],
        importsDirectory: 'workbox',
        importWorkboxFrom: 'local',
        navigateFallback: '/index.html',
        navigateFallbackBlacklist: [/^\/bundle/],
        precacheManifestFilename: 'workbox.manifest.js?[manifestHash]',
        swDest: path.join('..', 'workbox.js')
})

The problem is in the generated workbox.js:

self.__precacheManifest = [].concat(self.__precacheManifest || []);
workbox.precaching.precacheAndRoute(self.__precacheManifest, {
  "directoryIndex": "/index.html"
});

workbox.routing.registerNavigationRoute(workbox.precaching.getCacheKeyForURL("/index.html"), {
  blacklist: [/^\/bundle/],
});

.getCacheKeyForURL() is returning undefined. The precache key shouldn't have the the leading forward slash. Everything works if I remove it:

workbox.precaching.getCacheKeyForURL("index.html")

In searching I noticed the following PR #1874 which uses navigateFallback for the cache key. Perhaps this should instead be using directoryIndex?

I also see that registerNavigationRoute() has been deprecated, so perhaps this issue is late and can be ignored. I will test the next @5.0-alpha when #2143 is merged.

[wallzero]

I've managed to fix the issue by prefixing the applications <base> href to navigateFallback. Now .getCacheKeyForURL() finds a match.