Another weird episode on my Mac

I'm not sure what brought this on...

Some months ago (less than six, but more than one), after an OSX update of sorts, Messages stopped showing peoples' names and began just showing the phone numbers.

Quite irritating. For any given messager, for the very few I have a photo of, I could see that, or, if the number matched a Contacts entry, I could see first and last initials ("AB"), but that darn number was always there in place of the name.

For computers, it's more efficient to use the numbers. But for people, well, we don't work like that. Partly because we tolerate duplicated names ("John Smith") where the computer cannot.

If you look online you can't find a solution. Apparently talking to Apple Tech Support won't get it done either. (???)

Well, ok, you CAN find solution online.

Here's my situation: all works great on my iPhone. But suddenly not on my Mac. Mac running High Sierra.

Nothing I do/try fixes it.

Until this:

1. Close the contacts app. Close Messages. Close Mail.
2. Go to ~/Library/Application Support/ (in Finder, using command-shift-G)
3. Rename the "AddressBook" folder to something like "AddressBook-old" just to be safe
4. Open the contacts app. Wait a couple minutes for it to resynchronize
5. It will create a new AddressBook folder that syncs to icloud properly. Wait until you see all your contacts re-appear.
6. If it's all dandy delete the renamed AddressBook folder

OK, if it's NOT all dandy, quit Contacts, delete the NEW AddressBook folder, and rename the old one back to AddressBook.

But this worked for me. (other folks found that making sure the phone number format lined up exactly the same did the trick--but I would argue that that is a different problem)

Really don't know why. If *I* were the author of the software, Contacts, Messages, all that contacts-using stuff, this wouldn't ever happen, and some other annoyances would also go away. 

All this "Account" stuff in OSX has got some fundamental issues, primarily associated with what happens when you have a bunch of accounts and old ones go away.

Mail has never had this problem for me, but maybe that one is better about multiple accounts.

The inconsistency is annoying.