Blocked Users Show Up in "To" Autocomplete Field

Hey Berdir,

In my testing of "User Blocking Rules," I did notice one thing that is either a bug or a feature request. Basically, if a rule is set at admin/config/messaging/privatemsg/block to prevent sending to a particular role, then users of that role should not show up in the "To" autocomplete field when sending a new message.

Here's a use case: The site admin may want to prevent users other than site administrators from sending messages to regular authenticated users (such as if Private Messaging is being used for an admin notification system). This rule can be set up, but then other users will still see authenticated users listed in the "To" autocomplete (even though they will be prevented from sending to them). This could get cumbersome for sites that have tens of thousands of authenticated users. Also, the site administrator may not want to use all authenticated users on the site to show up in the autocomplete for security reasons.

So here's the question: Would it create a lot of overhead and performance issues to first check who is permitted to show up in the autocomplete?

Also, we have the issue of individual users blocking other users: It would be better if users who are blocking you didn't show up in the autocomplete, but I'm wondering about the overhead issues of having to check if you've been blocked by anyone when writing a new message.

What do you think?

Best,
Ben

P.S. Do roles who do not have "Read messages" permission show up in the autocomplete? I wasn't sure about that one.