[Offline] Bug fix - cached files now serving in offline too

[bekliev]

I'm catched this issue on Windows 10.

Step-by-step what happens:

const files = [
    // ...
    "favicon.png",
    // etc. (cache-able files)
];

const to_cache = shell.concat(files).filter(n => n !== '.DS_Store');
const cached = new Set(to_cache);


// Our listener
self.addEventListener('fetch', event => {
    // ...

    /*
     * We cannot pass this condition, cause of: url.pathname is equal to "/favicon.png"
     * the source: `cached.has(url.pathname)` which will become `cached.has("/favicon.png")`
     * this fix will do the thing: `cached.has(url.pathname.slice(1)` which will become `cached.has("favicon.png")`
     */
    if (url.host === self.location.host && cached.has(url.pathname.slice(1))) {
        // serving...
    }

    // ...
});

[iztsv]

The same issue on macos. cached set contains urls which don't start with /, but url.pathname always starts with /.

[bekliev]

I think this PR #138 would be better to approve and merge instead of mine.
Anyway check out both, please.

[benmccann]

See sveltejs/sapper#1210. We should figure out where we want to fix it