Bad Request (400) when opening PayPal Payment Popup (eg clicking Pay with PayPal during checkout)

[MFRWDesign]

Bad Request (400) when opening PayPal Payment Popup (eg clicking Pay with PayPal during checkout)

[seand7565]

Hey Thomas! Some initial thoughts here:
As you mentioned, this is probably the result of ill-formatted data somewhere. Initially, I thought this could be an issue with the data being sent (which is formatted here) - because PayPal is very picky that all numbers add up - but in that case, the PayPal dialogue should quit, a JS alert should pop up for the customer, and an error message should be logged to the server log.

But in this case, that doesn't appear to be the case. This is the request that it should be performing, but seems like something is breaking before then. My guess is it'll be something with the paypal_order not building correctly. I'm not sure how customized your installation is, is there any reason you can think of that would make the paypal_order not build correctly?

[MFRWDesign]

Looks like we finally figured this one out, or more or less. Since the bug only happens when BASIC AUTH is enabled, which we have enabled for our staging server, it seems pretty clear that's the cause. Turning it off produced another error, but as it turned out, that was related to our test credentials.

Once we had Basic AUTH off and switched in the live credentials. It worked just fine. For now, maybe we should just add a note about it in the README since everyone's setup is likely to be a bit different.

Beyond that, I think we might be able to fix this by conditionally adding the Basic Auth credentials directly to the request URL (if the BASIC_AUTH env was set). eg something simple like:
https://#{ENV['BASIC_AUTH'].present? ? ENV['BASIC_AUTH'] + "@" : ""}staging-server-on-heroku.com/solidus_paypal_commerce_platform/paypal_orders/R684159333?payment_method_id=3&order_token=gtZcM_4Ksdb4aGFZjCah7Q