Delete I18n logic from engine

[johnnyshields]

The lines deleted in the PR are unnecessary, and they inadvertently change the I18n behavior of your entire app.

(In my case, it breaks the i18n-js gem's export, but others may be affected.)

It looks like this was added by @jasl here: 78fa331

My guess was he wanted the English error messages for Doorkeeper to appear even when using a different default locale. But the Doorkeeper gem should NOT reconfigure your Rails app globally in order to achieve this goal!

[tute]

Thanks for your contribution!

I agree that doorkeeper shouldn't silently reconfigure your app, and that should be considered a bug. That said, this is a backwards incompatible change, which in turns will bring back the bug described in #627.

How can we keep that bug fixed, while being considerate of the application's configuration? Is there a way to fallback only the translations with a doorkeeper. prefix?

[johnnyshields]

#627 is not a bug. It is expected behavior of Rails if:

1. You do not have a translation for a given locale AND
2. You have not set locale fallbacks in your app.

This is how I18n works for every app and gem in existence, and it's not up to Doorkeeper to force an override on the user.

[johnnyshields]

I think we can put a warning in the gem log when upgrading:

****
As of version x.y.z Doorkeeper no longer sets I18n.fallback_locales by default. 
If you are using I18n in your app, please either ensure you have fallbacks in your
Rails configuration (see: http://guides.rubyonrails.org/i18n.html) or use one of our
translations at https://github.com/doorkeeper-gem/doorkeeper-i18n
****

[tute]

#627 is not a bug. It is expected behavior of Rails if:

You do not have a translation for a given locale AND
You have not set locale fallbacks in your app.

This make sense.

About backwards incompatibility, we didn't yet release v4, so we can be backwards incompatible. Merging, thank you!

[tute]

Ouch, we should have added this context to the commit message. I'll add it to NEWS when we prepare a new release.

[johnnyshields]

Cheers!