@Alexia Can you specify how this broke extensions? E.g. through a hook? If so, please state which hook and include an example of that worked before and now doesn't.
Looking through the code modified by this patch, it seems the extrainput key is only used internally and not exposed through any hooks that I could find. I did find a few other unrelated methods in the same class that do still use the key extraInput and are exposed.
The introduction of this class can be traced to 3617c982c9db7 which is the introduction of AuthManager for the login page. Its commit message includes the following text which seems relevant:
- Adding fields to the login/signup forms by manipulating the template via the extraInput/extrafields parameters is not supported anymore.
I suspect that maybe this patch was written in the hopes that it restores compatibility, but without knowing whether this worked for you, and how, I'm hesitant to merge it. In its current state, I suspect that maybe the patch may've been rebased from code that predates AuthManager. If that is the case, it would explain why the patch may've worked for you, but doesn't work on current master, where the code (albeit looking the same) is no longer called the same way.
The issue was that when I submitted this patch 1.5 years ago that it broke several extensions that relied on it and had not been updated yet.(Such as ConfirmEdit.) Looking at my current local code base all of those extensions have been updated and no longer rely on it. This can be abandoned.