New with Yosemite, "set selected messages of the front viewer" FAILS.

[wcattey]

Having gotten rather annoyed with how Yosemite broke the action of the right arrow key to bring me to the first unread message of a conversation, I decided to try out some of the available AppleScript that selects the next unread message.

The most robust version I found was:

	try
		tell application "Mail"
			activate
			tell the front message viewer
				set unreadMessages to (the messages whose ¬
					read status is false) as list
				if (count of unreadMessages) is not 0 then
					set selected messages to {the first item of unreadMessages}
				else
					beep
				end if
			end tell
		end tell
	on error error_message
		beep
		display dialog "Error looking for next unread message: " & ¬
			return & return & error_message buttons {"OK"} default button 1
	end try

The version submitted to this forum by Bruce Philips in 2009 doesn’t seem to work in Mavericks.

http://macscripter.net/viewtopic.php?id=17906

So I decided to bite the bullet and learn AppleScript, and to study the Mail.app dictionary.

I discovered that indeed Yosemite returns the list of unread messages in unsorted form, compared to Mavericks.
I crafted the AppleScript below to show me EXACTLY what was being chosen so that I could confirm all was well:

try
	tell application "Mail"
		activate
		set outStr to ""
		set selMessage to null
		set unreadMessages to the messages of the front message viewer ¬
			whose read status is false
		repeat with thisMessage in unreadMessages
			if selMessage is null then
				set selMessage to thisMessage
			else
				if (date received of thisMessage) is less than (date received of selMessage) then
					set selMessage to thisMessage
				end if
			end if
			set newStr to the subject of thisMessage & ": " & ¬
				(date received of thisMessage) & return
			set outStr to outStr & newStr
		end repeat
		display dialog outStr & return & "Selected: " & ¬
			the subject of selMessage
		set selected messages of the front message viewer to selMessage
	end tell
on error error_message
	beep
	display dialog "Error looking for next unread message: " & ¬
		return & return & error_message buttons {"OK"} default button 1
end try

And this works just fine under Maverics, but under Yosemite, NO message is selected.
(Actually there is a failure mode where one is selecting into a conversation that is closed,
but I’ll leave that as question #2 when we get the basic thing working again under Yosemite.)

In the helpful article from this site on using Dictionaries
http://macscripter.net/viewtopic.php?id=24777

We see the bottom line:

Some applications don’t always conform to their dictionaries. Apple’s own Mail program comes to mind here, as it has been plagued with dictionary inaccuracies and things that don’t work since, I think, Panther. So if a command or class doesn’t behave as it should, check with other scripters or here at Macscripter to see if others have a work-around.

So…

Does anyone know how to get Mail.app in Yosemite to actually select a message?
The way that used to work now fails.