Use of fetch API breaks cordova apps

[gpiffault]

mapbox-gl-js version: 0.51.0

browser: Chrome 70 (webview)

#7371 introduces a bug in cordova apps loading local assets. The fetch API doesn't support the file: scheme whereas xhr does (JakeChampion/fetch#92 (comment)) so when style specification or images are stored locally, they won't load after 0.51.0 (works fine up to 0.50.0).

For reference, I commented on the commit here eec8cd5#commitcomment-31351193

[mourner]

Yeah, we should probably switch to XHR when requesting a URL with a file protocol. Would you like to do a PR with the fix? cc @kkaefer

[kkaefer]

It looks like no browser allows access via file:// URLs anyway´ due to security constraints. E.g. Chrome reports:

Access to XMLHttpRequest at 'file://test/integration/tiles/14-8803-5375.mvt' from origin 'file://' has been blocked by CORS policy: Cross origin requests are only supported for protocol schemes: http, data, chrome, chrome-extension, https.

[gpiffault]

This behaviour is disabled in the webview cordova uses (only for xhr, not for fetch, it's probably not possible for fetch). Unfortunately I think it's not trivial to test it out, you need to install cordova, make a sample project and run it on a device. I can help with the testing.

[mourner]

@kkaefer it's possible in certain environments like Cordova. We had related PRs before, e.g. this one #6610

[ansarikhurshid786]

I am also using ionic 3 which use cordova for building ios and android application. In my application it is working fine. I seen my application running on local web server.

[kkaefer]

@gpiffault This should be fixed in #7818.

[gpiffault]

@kkaefer Thanks. Actually it didn't directly fixed my use case besause I used relative URLs to load the local assets so the regexp isn't enough in this case. It works when I convert my URLs to absolute but it's not quite straightforward, you might get new bug reports about this.

[denis1994]

I have the same problem. I use mapbox in react project with cordova but my pins images aren't loaded. Downgrading to 0.50.0 works fine. I also use relative paths.

[denis1994]

@gpiffault I will test your commit and report here. Perhaps they can take it to the actual version.