Confusing/Unhelpful Error at Login When XML-RPC Is Blocked

[SiobhyB]

Expected behavior

If I enter the URL for a WordPress site that blocks XML-RPC, I expect to receive a helpful error message that informs me why I'm not able to log into that site via the app.

Actual behavior

The following error appears when a URL for a WordPress site that blocks XML-RPC is entered:

"We're sure this is a great site - but it's not a WordPress site, so you can't connect to it with the app."

Screenshot:

Steps to reproduce the behavior

1. Navigate to the app's login screen and select the "Log in by entering site address" option.
2. Submit the URL to a site that blocks XML-RPC.

Tested on iPad mini, 10.9 of WordPress for iOS

cc-ing @etoledom, who worked on these error messages during a hack week in March:

https://a8c.slack.com/archives/C9JMWK5HQ/p1520333424000220-slack-happier-hes

I've also opened wordpress-mobile/WordPress-Android#8459 for Android.

[aerych]

A few thoughts:

• We need to harmonize the messages shown between WPAndroid and WPiOS.
• This might be a good time to switch from our current self-hosted discovery logic to querying public-api.wordpress.com/rest/v1.1/connect/site-info or use this call as a fall back.
• When all else fails we might check for the presence of the WP REST API to confirm we're dealing with a self-hosted site.
• In cases where we can't identify a WordPress site it would be nice if we could tweak the message shown to allow for cases the apps are wrong.