How to get "emacsclient --eval x" to DWIM when Emacs is not started

[Mathias Dahl]

How can I get "emacsclient --eval x" to DWIM when Emacs is not
started? I have tried the following:

emacsclient -e '(message "Hello!")' -a emacs

But that does not work. What happens is that Emacs, when started as
the alternate editor, tries to open a file with the name ''(message
"Hello!").

For normal operation, i.e. not using --eval but just for opening a
file, -a emacs works well and does what I expect. Why does not --eval
do the same? I have, of course, (server-start) in my .emacs file.

As far as I can see, the manual does not mention this case.