Unable to find mlb file

[ahmedriza]

Many thanks for this excellent plugin. Just started using this after coming to neovim (having been an emacs user for all of my life!).

Everything works very well so far, except that def-use doesn't appear to be working, although I do have an mlb file setup correctly, and I can manually run mlton to generate the du file.

As we can see, the plugin is unable to find the mlb file. The directory contains two files:

hello.sml
prog.mlb

prog.mlb contains the following

local
  $(SML_LIB)/basis/basis.mlb
in
  hello.sml
end

And the following works correctly:

mlton -prefer-abs-paths true -show-def-use prog.du -stop tc prog.mlb

OS: Mac OS 14.3.1.
NVIM: v0.9.5

Any thoughts on what could be going wrong?