Wp-calypso: Signup: Unable to proceed at last step

[v18]

This issue is not reproducible each time, here are approximate steps:

1. Sign up at wordpress.com/start
2. Go through signup (I chose porfolio, a .wp.com address, and a free plan)
3. See message that things are being set up in the background
4. See button that asks me to continue
5. See that button doesn't work, and see this error message:

Uncaught DOMException: Failed to execute 'pushState' on 'History': A history state object with URL 'https://valtest20180705.wordpress.com/' cannot be created in a document with origin 'https://wordpress.com' and URL 'https://wordpress.com/start/user'.

Apologies, I don't have screenshots or more detailed info!

This is not reproducible every time I sign up, maybe it's an A/B test?

@gwwar is thinking maybe we're using page.js instead of a normal link.

[gwwar]

Reading the code, on the processing screen was pass through a click handler:

https://github.com/Automattic/wp-calypso/blob/6a31cd6eddd23f83bcf2f822397b2ce55126e507/client/signup/processing-screen/index.jsx#L271-L273
Tracing this back further, we pass through:

https://github.com/Automattic/wp-calypso/blob/6a31cd6eddd23f83bcf2f822397b2ce55126e507/client/signup/main.jsx#L487-L490

Which if we follow that, internally calls handleLogin:
https://github.com/Automattic/wp-calypso/blob/6a31cd6eddd23f83bcf2f822397b2ce55126e507/client/signup/main.jsx#L311-L325

If we're attempting to navigate outside of the current origin of say WordPress.com, it's problematic to use page.js page( destination ). The browser history API will complain because we're only allowed to push history state on the same origin for security reasons.

https://developer.mozilla.org/en-US/docs/Web/API/History_API#The_pushState()_method

[meremagee]

Caught this one today as well!
Chrome Version 67.0.3396.99 (Official Build) (64-bit). Console for your viewing pleasure:

Appears log in is successful (hit "login" after site creation hung):

[mattwiebe]

This reminds me of an old classic #908