Isolate Users in Groups

[Iman Rameshni]

Hello all, I am a Jira admin and I manage several projects, recently I created separate groups for each project, now I need to isolate group members, I mean I need to somehow configure groups so that a group member only can find other group members even if he/she search for a person in People section he can only find his group members and not find other groups members; is it possible in Jira? and how can I configure it?

[Alexander Pappert]

in project permission, you can configure the groups which can be an assignee of the issue.

user a is in group a

user b is in group b

permission says only group a members can be assignee

so user a can not find/see user b

[Nic Brough -Adaptavist-]

No, Jira has no way to hide people - you can either see and search for everyone, or you can not.  The "browse users" permission in global permissions is simply on or off for a person.

[Iman Rameshni]

Thanks,
Then if I disable "browse users" permission, can users assign a task to another user?

[Nic Brough -Adaptavist-]

Yes, they can, but they'll need to know the name of the other user, as they'll have to type it in full to get it selected.

[Iman Rameshni]

Thanks

[Iman Rameshni]

I implemented the discussed solution and everything is working perfectly, ther is only one problem in @mentioning users in tasks and issues.
Is there any way to solve it?
@Nic Brough -Adaptavist- 
And again thanks for your helpful comments.

[Nic Brough -Adaptavist-]

We don't know, you have not told us what the problem is (or what you have "implemented")

[Iman Rameshni]

Actually I created separate groups for different project, and also I created permission schemes for each project, so that each group can only have access to their project;
Then I disabled "browse users" permission on global level.
Now created tasks can be assigned to people in the group but people can not be mentioned in the comments.
Is there any way to solve the mentioning problem with current configuration?
I hope I could explain the situation.

[Nic Brough -Adaptavist-]

You need browse user to be able to look up people to mention.  This is not a "problem", it's by design, you've chosen to turn it off.

[Iman Rameshni]

Thanks,
by problem I meant my problem :D
so if I enable "browse users" permission, is there any way to disable users from searching other users that are not in the same group with them?

I need to stop users from searching and seeing other users that are not working on the same project with them; actually that's my main goal.

[Nic Brough -Adaptavist-]

I already explained how the lookups worked in my original answer.

I am sorry that it was not clear that you can't do what you're asking, user lookups are flat can or cannot.