`cabbrev` user commands are not shown

[steliyan]

I am not sure if this is even supposed to work, but these cabbrev doesn't seem to work:

vim.cmd([[
  cabbrev <expr> SessionSave getcmdtype() == ":" && getcmdline() == "SessionSave" ? "SaveSession" : "SessionSave"
]])

Maybe the registration order matters? Should this be done before or after the cmp-cmdline is loaded?