Display dialog to a remote machine via EPPC - macos

Question

How can I send a display dialog to a remote machine via EPPC? I believe Scripting Addition Security in the release notes discusses the issue but I have not been able to resolve it yet. Release Notes
Attempt 1
using terms from application "Finder"
set remoteFinder to application "Finder" of machine "eppc://user:password#host"
tell remoteFinder to display dialog "Hi!" buttons {"A", "B"}
end using terms from
Attempt 2
The application "dispD.app" is saved on the remote machine and should accept the yourMessage parameter.
on run {yourMessage}
display dialog yourMessage buttons {"A", "B"}
end run
I run this script from the local computer:
using terms from application "Finder"
set remoteFinder to application "Finder" of machine "eppc://user:password#host"
tell remoteFinder to run script file "path:to:my:dispD.app" with parameters {"Hi!"}
end using terms from

Answer 1

I think what you want to do may be impossible to do directly, although it's so hard to find docs on this that I'm not 100% sure. Various threads at MacScripter (such as this one) and on the Apple forums indicate a variety of problems talking to OSAXen ("Scripting Additions") over EPPC. (The threads get a bit confusing, because all of them diverge into red herrings, but I think some of them have relevant information.) And the "display dialog" command is not part of Finder (or System Events), it's part of the StandardAdditions OSAX.
This is actually hard to test from within AppleScript, because OSAX additions are pulled in automatically. But from appscript, you can manually attach an OSAX to an application like this:
sa = osax.ScriptingAddition('StandardAdditions', name='Finder')
sa.display_dialog('hi')
As expected, this works. while this gives an "unknown property, element, or command":
f = app(name='Finder')
f.display_dialog('hi')
Now, if I do an actual Finder command, like this:
f.windows()
Everything works. And if I want to remote that:
rf = app(url='eppc://test:test#localhost/Finder')
rf.windows()
No problem. But now:
sa = osax.ScriptingAddition('StandardAdditions', url='eppc://test:test#localhost/Finder')
sa.display_dialog('hi')
This works on 10.5, but not on 10.6, 10.7, or 10.8. (Well, out of the 8 machines I have access to, it works on the one that's running 10.5, but not on any of the 7 running 10.6+).
So, I think this is your problem.
As for solutions, I can think of a few hacky ways around this:
Instead of using remote scripting, use ssh + local osascript.
Use cocoadialog, pashua, etc., and drive them with do shell script, instead of using display dialog. (This will require you to have the respective tool on the remote target machine, not the local machine.)
Remote-script some app that can display dialogs natively, instead of relying on StandardAdditions. (I don't know if any of the stock apps have any way of doing this, so this might require installing something on the remote machine, in which case you might as well just use cocoadialog.)