How can I set WM_CLASS for Emacs 27?

Question

I use scratchpads in XMonad (my WM) extensively for quickly capturing (notes, TODOs etc) from anyhwere. I have an instance of Emacs running permanently in a workspace, and launch emacsclient as my scratchpad.

XMonad relies on WM_CLASS property of the frame(?) to identify if it should start new emacsclient instance, or if it should reuse it started previously. Before Emacs 27, this is how I used to start emacsclient from XMonad:

emacsclient -c --frame-parameters='(quote (name . "scratchmacs"))'

Before Emacs 27, doing a xprops | grep WM_CLASS would return "scrathmacs", but Emacs 27 keep giving "Emacs" instead. As a result, everytime I call my scratch-pad, a new window for emacsclient opens up :-(

I have done a bunch of googling and read through the documentation (albeit quite non-methodically), but got nowhere.

Evaluating (assoc 'name (frame-parameters)) in new emacsclient frame gives correct answer, i.e scratchmacs (but xprop for this frame still says emacs).

How can I set WM_CLASS of my choice for new emacsclient frames?

Answer 1

I've pinged the bug report as it's still happening in Emacs 28, but in the meantime, I use the following:

# emacs.sh:
# call as ./emacs.sh [<file1>] [...]

flock "/run/lock/emacs-wmclassfix-$USER" bash -s "$@" <<'EOF' 
{
        emacsclient --no-wait --create-frame "$@" ||
        exec emacs --name emacs-title -f server-start "$@"
} &
EOF

If the server is started by calling emacs directly instead of letting emacsclient create one, then all goes to plan. This fully fixes the problem for me, without loss of functionality.