Not possible to override base_url in production

Hi Ryan, I haven't had the chance to look at your patch yet, but it appears you are experiencing this issue: #2727863: Multiple domain names
Can you please try passing the uri parameter to cron and confirm it sorts out the problem?

I was running into the same issue with our Pantheon hosted sites using this module. The patch in #10 is working well for us. We've got a mix of both nodes and taxonomy terms set to show up in the sitemap and both are now being added with our preferred base URL.

Thanks for the patch Ryan, it appears there is a wider interest to implement this, so I will look into this next.

My review of the patch (without having applied it yet):
Why are #9 and #10 so much different and which one is right for dev? Please don't post patches against the stable version. Also it seems strange to use str_replace to replace the string coming from the URL object and I feel there must be a cleaner way. The URL class doesn't seem to have an option to alter the URLs base path. Anybody has an idea how to cleanly implement this?

There is an API within simple_sitemap for getting the module's settings, use the simple_sitemap.generator service's getSetting() method instead:

$base_url = \Drupal::service('simple_sitemap.settings')->getSetting('base_url')

instead of

$config = \Drupal::config('simple_sitemap.settings')->get('settings');
$base_url = $config['base_url'];

I feel like this next line should have its own method (if we decide to use str_replace), but this is nitpicking:

$urls[$language->getId()] = str_replace($GLOBALS['base_url'], $batch_info['base_url'], $url_object->toString());

Thanks for your time!

Please do not forget to pull the new dev version first, as there has been lots of code refactoring to improve testability.

Attached is a reroll of patch in #10 I am using on Platform.sh against 8.x-2.x-dev.

@hitfactory Thanks for rerolling, however some of my critique on the patch from #15 still remains.
I've changed the logic to the point I'm happier with the code and commited to dev. The logic could still be improved though. I've also added a form validator and a couple of tests. Can you guys test the functionality for me?